Symposium CJ
Advances in Electroceramics

Session CJ-1 - Dielectrics and Microwave Materials

CJ-1:IL01  Ferroelectricity in Ag(Nb,Ta)O3 Ceramic System
D. SUVOROV, M. SPREITZER, L. LI, D. KLEMENT, Advanced Materials, Jozef Stefan Institute, Ljubljana, Slovenia

The Ag(NbxTa1-x)O3 system has received considerable attention in the recent years due to its attractive dielectric properties, especially the combination of high dielectric constant, low dielectric loss and temperature stability of dielectric constant at microwave frequencies. The solid solutions from the system undergo rich sequence of displacive phase transitions and their effect on the dielectric properties have been investigated thoroughly. Furthermore, they also affect materials` ferroelectric properties and ferroelectricity-related dielectric tunability, which are interesting and important issues that have not been investigated adequately so far.
In the present work Ag(NbxTa1-x)O3 ceramics were prepared using conventional solid-state reaction. Formation of the matrix phase, as well as its decomposition were carefully followed in relation to ceramic`s density. Consequently, for each solid solution optimal sintering temperature was selected. As-prepared ceramics were analyzed with respect to their RF and MW dielectric properties. Furthermore, due to interesting polarization-electric field relationship ferroelectricity and dielectric tunability of the ceramics were investigated with a high electric field. Depending on the composition and the maximum applied electric field we observed various ferroelectric-like hysteresis loops. Correspondingly, interesting dependence of dielectric constant on DC-bias was also observed, which will be further discussed during our contribution.


CJ-1:IL02  Dielectric and Piezoelectric Enhancement of Barium Titanate-based Nano-complex Ceramics based on Different Heteroepitaxial Interfaces
S. WADA, University of Yamanashi, Yamanashi, Japan

Barium titanate (BaTiO3, BT)-based nano-complex ceramics with various perovskite-structured materials, i.e., such as potassium niobate (KNbO3, KN), bismuth ferrite (BiFeO3, BF) and so on, were prepared at temperature below 230 ˚C by solvothermal method. In this study, KN had larg-er cell volume by 0.5 % than that of BT, while BF had smaller cell volume by 1 % than that of BT. Therefore, we expected that the dielectric properties for the BT-KN nano-complex ceramics were quiet different from those for the BT-BF nano-complex ceramics. Their interfaces were assigned to epitaxial interfaces by transmittance electron microscope (TEM). Moreover, X-ray diffraction (XRD) measurement with Rietveld refinements revealed that in the interfaces for BT-KN and BT-BF, there were structure-gradient region (SGR). Moreover, these nano-complex ce-ramics prepared in this study were porous with a porosity of around 25 ~ 35 %. The dielectric measurements showed that for the BT-KN nano-complex ceramics with KN/BT ratio of 1, the dielectric constant was 300 at 20 ˚C and 1 MHz, while for the BT-BF nano-complex ceramics with BF/BT ratio of 1, the dielectric constant was 70 at 20 ˚C and 1 MHz. To explain the results, we proposed SGR model dependent of lattice mismatch and material hardness.


CJ-1:L03  NiO and CeO2 Thin Films as High k Gate Dielectrics for Wide Band Gap Semiconductors
R. LO NIGRO, F. ROCCAFORTE, G. FISICHELLA, G. GRECO, P. FIORENZA, Istituto per la Microelettronica e Microsistemi (IMM)-CNR, Catania, Italy; S. BATTIATO, G. MALANDRINO, Dipartimento di Scienze Chimiche, Università degli Studi di Catania, and INSTM udr Catania, Catania, Italy

Wide band gap semiconductors are considered suitable candidates for high frequency and high power electron devices. In particular, GaN-based semiconductor field effect transistor (MESFET) and high electron mobility transistor (HEMT) devices have shown excellent progress, but a few significant difficulties in device performance still exist. Principle problems arise from the leakage current and parasitic resistance. One of the main issue to be addressed is the growth of a suitable dielectric oxide to be grown on GaN heterostructures to promote inversion, reduce gate leakage and provide surface passivation. Epitaxial oxides (NiO) thin films, such as NiO and CeO2, have been grown by metal-organic chemical vapor deposition (MOCVD) on AlGaN/GaN heterostructures. All the critical growth parameters have been studied in order to optimize the deposition process of the thin films suitable for applications in GaN-based devices. Optimized operative conditions determined the growth of epitaxial thin films which exhibited permittivity values (11.7 and 26), close to that of the bulk materials. This approach is advantageous with respect to other reported methods, such as the thermal oxidation of Ni films, because of its higher reproducibility and better film quality. Hence, the obtained epitaxial films can be very promising as gate dielectrics for AlGaN/GaN transistors technology.


CJ-1:IL05  Synthesis and Characterization of KNbO3 Nanomaterials
WOONG KIM, Department of Materials Science and Engineering, Korea University, Seoul, Republic of Korea

The synthesis of KNbO3-based nanowires and nanotubes and their piezoelectric and optical properties will be presented. KNbO3 nanomaterials can be produced by various synthesis methods such as hydrothermal reaction and sol-gel process. Hydrothermal reaction produces high quality single crystalline KNbO3 nanowires with different phases, which lead to different energy conversion and frequency generation efficiency. On the other hand, KNbO3 nanomaterials can be doped more easily when prepared via sol-gel process, which may led to improvement of piezoelectric and optical properties. Polycrystalline KNbO3 can be prepared in various forms such as nanowires, nanotubes, and thin-films via the sol-gel process. Our results imply that novel synthesis routes to KNbO3 nanowires and nanotubes may find energy harvesting and nanobiotechnological applications.


CJ-1:L06  Low-Firing PZT-Multi-Layer Bending Transducer Using Ag Inner Electrodes
A.J. MEDESI, T. HANEMANN, Laboratory for Materials Processing, Department of Microsystems Engineering, IMTEK, University of Freiburg, Germany

We present a fabrication technique for a piezoelectric multi-layer bending transducer via co-firing process with cost-effective internal electrodes for integration in a frequency-tunable vibration energy harvester.
Starting material is a PZT powder with "hard" piezoelectric characteristics (Qm = 2000), perfectly suited for generator built-up. At room temperature crack-free drying ceramic green tapes with E-Moduli above 250 MPa and no dependence of their mechanical properties on casting direction were fabricated by tape casting method from a new phthalate-free slurry composition with a solid content of 73 wt%. The most suitable binder-type of polyvinylbutyral was determined by performing tensile testing on green specimens.
For utilization of Ag as an inner electrode between ceramic layers, co-firing temperature should be lower than the melting point of Ag. However, a sufficient densification of the piezo-ceramic material occurs at temperatures higher than 1,100 °C. We compared the effects of Li2O, Li2CO3, CuO, PbO and La2O3 as sintering aids and obtained the highest densification below 900 °C (16%)for Li2O. Using 0.1 wt% Li2O added PZT ceramics, a multi-layer stack with screen-printed Ag inner electrodes was successfully fabricated via co-firing for integration into a harvester.


CJ-1:L07  Structural and High Frequency Dielectric Properties of Ba(ZrxTi1-x)O3 Films prepared by Reactive Magnetron Sputtering using Metal Targets
JINWOONG KIM¹, H. FUNAKUBO², H. SHIMA¹, K. NISHIDA¹, T. YAMAMOTO¹, ¹National Defense Academy, Yokosuka, Kanagawa, Japan; ²Tokyo Institute of Technology, Japan

Ba(ZrxTi1-x)O3 (BZT) films is a possible choice as an alternative to BST in the fabrication of ceramic capacitors because Zr4+ is chemically more stable than Ti4+. We investigated the tunable ferroelectric behavior of BZT films to determine the ferroelectric and tunable properties of compounds from the BZT films. The BZT films were deposited on (100)MgO and (100)Pt/(100)MgO substrate by a RF magnetron reactive sputtering method using metal targets. Compositions of BZT films were controlled by number of Ba and Zr metal pieces. All the BZT films crystallized into a single perovskite phase by optimum reactive gas flow ratio. Moreover, it was found that all the films on (100)MgO substrate were only (001)/(100) orientated and the ratio of Ba/Ti was stoichiometry. From reciprocal space mappings results with different Zr contents, it was confirmed that BZT films epitaxially grew on MgO substrates. AFM profiles showed that the average grain size and RMS roughness of BZT films monotonically decreased with increasing Zr content. A tunability of 75% and a loss tangent of 0.04 have been achieved for an optimized sample measured at 1 MHz and room temperature. We are going to discuss about of electrical properties of BZT films for high frequency tunable ferroelectrics at my presentation.


CJ-1:IL11  SrLn2Al2O7 (Ln = La, Nd, Sm) Microwave Dielectric Ceramics and their Modification
XIANG MING CHEN, LEI YI, XIAO QIANG LIU, LEI LI, Laboratory of Dielectric Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou, China

SrLn₂Al₂O₇ (Ln = La, Nd, Sm) ceramics were proposed and investigated as new candidates for ultra-low loss microwave dielectric materials. These ceramics indicated the Ruddlesden-Popper structure of general formula A_n+1B_nO_3n+1 with n = 2, which was composed by n perovskite layers alternating with one rock salt layer. Very high Qf value combined with a dielectric constant around 20 were obtained in the present ceramics, where the near-zero temperature coefficient of resonant frequency varied from negative to positive with changing Ln from La to Sm. The best combination of microwave dielectric characteristics was obtained as the following: ε_r = 18.2, Qf = 71,680 GHz and τ_f = -22.1 ppm/°C for SrLa₂Al₂O₇; ε_r = 20.5, Qf = 65,500 GHz and τ_f = -4.3 ppm/°C for SrNd₂Al₂O₇; and ε_r = 21.6, Qf = 64,680 GHz and τ_f = +4.0 ppm/°C for SrSm₂Al₂O₇. The microwave dielectric characteristics could be significantly improved by Ca-substitution for Sr, and a Qf value up to 130,000GHz was obtained in (Sr,Ca)La₂Al₂O₇ solid solutions together with the increased ε_r and controlled τ_f.


CJ-1:IL12  LTCC Integrated Piezoelectric Structures
M. SOBOCIÑSKI, J. JUUTI, H. JANTUNEN, Microelectronics and Materials Physics Laboratories, Department of Electrical Engineering, University of Oulu, Oulu, Finland

Piezoelectric components play key role in modern electronics. However to connect the piezoelectric structures to the outside world through packaging with an inexpensive manner is a challenge. The Low Temperature Co-fired Ceramic (LTCC) technology with embedded piezoelectric structures has been proposed as a one solution for this challenge. In the last ten years about one hundred papers have been published. In this paper the most feasible integration methods of piezoelectric structures and applications thus realized in the field of sensing, actuating and energy harvesting are reviewed and their advantages and limitations are discussed.


CJ-1:L14  BaTiO3 Ceramics Micro Structures new Fractal Frontiers
V.V. MITIC, University of Nis, Faculty of Electronic Engineering, Nis, Serbia, Institute of Technical Sciences of SASA, Belgrade, Serbia; V. PAUNOVIC, LJ. KOCIC, University of Nis, Faculty of Electronic Engineering, Nis, Serbia; S. JANKOVIC, Mathematical institute, SASA, Belgrade, Serbia; V. LITOVSKI, University of Nis, Faculty of Electronic Engineering, Nis, Serbia 

In this study, in order to establish grain shapes of sintered ceramics, new approach on correlation between microstructure-nanostructure and properties of rare-earth and other additives doped BaTiO3 and all electronics ceramics based on fractal geometry, related to intergranular contact surfaces and mathematical statistics calculations has been developed.
Fractal geometry has been used to describe complexity of the spatial distribution of BaTiO3-grains. The model of impedances, between clusters of ceramics grains, has been presented and calculations of microcapacitance generated in grains contacts of doped BaTiO3 have been performed.
Ву the control of shapes and numbers of contact surfaces on the level of the entire BaTiO3-ceramic sample, the control over structural properties of these ceramics can be done, with the aim of correlation between material electronic properties and corresponding microstructure. The fractal nature for analysis of the structure of ceramics providing a new approach for modeling and prognosing the grain shape and relations between the BaTiO3-ceramic structure, micro- and nano-, and dielectrical, ferroelectrics and all other electronic properties in the light of new frontier for higher level electronic circuits integration.


Session CJ-2 - Ferroelectrics, Piezoelectrics, Pyroelectrics

CJ-2:IL01  Interplay between Flexoelectricity and Nanodomains
G. CATALAN^{1, 2}, J. NARVAEZ², N. DOMINGO², S. SAREMINAEINI², J. OÈENÁSEK³, J. ALCALA⁴, B. NOHEDA⁵, HAIDONG LU⁶, A. GRUVERMAN⁶, ¹Institut Catala de Recerca i Estudis Avançats (ICREA), Catalunya; ²Institut Catala de Nanociència i Nanotecnologia (ICN2), CSIC-ICN, Campus de Bellaterra, Barcelona, Spain; ³New Technologies Research Centre, University of West Bohemia in Pilsen, Plzeò, Czech Republic; ⁴Department of Materials Science and Metallurgical Engineering, GRICCA, Universitat Politecnica de Catalunya, Barcelona, Spain; ⁵Zernike Institute for Advanced Materials, University of Groningen, The Netherlands; ⁶Department of Physics and Astronomy, University of Nebraska-Lincoln, NE, USA

The recognition of the importance and potential usefulness of domain walls in ferroic nanostructures and nanodevices has led to the emergence of the field of domain wall nanoelectronics. In parallel, and independently, there has also been an increased realization of the impact of strain gradient-induced polarization (flexoelectricity) in such devices. In this talk I would like show that these two topics are linked.
The connection between nanodomains and flexoelectricity runs in both directions, and accross lengthscales. Strain gradients generate flexoelectric polarization inside ferroelectric nanotwins and also inside domain walls. Also, the flexoelectricity generated by mechanically pushing with the tip of an atomic force microscope against the surface of a ferroelectric is capable of inducing ferroelectric switching, and thus is an effective tool for generating ferroelectric nanodomains and controlling the position of domain walls with nanoscopic accuracy. Conversely, the persistence of polar nanodomains in the paraelectric phase of some ferroelectrics and relaxors can artificially enhance their bending-induced polarization. The short summary is that flexoelectricity affects nanodomains, but, conversely, polar nanodomains can also affect bulk flexoelectricity.


CJ-2:IL02  Pyroelectric and Piezoelectric Properties of Nano-crystals grown inside Alumina Pores
S. BERGER, Faculty of Materials Science and Engineering, Technion, Haifa, Israel

Pyroelectric and piezoelectric properties of nano-crystals is of high technological and scientific interest for developing highly sensitive miniaturized sensors, detectors and actuators. Various non-linear non-perovskite dielectric nano-crystals were grown in our lab inside a highly dense array of amorphous alumina nano-pores such as Tri-Glycine Sulfate (TGS), Sodium potassium double tartrate hydrate known as Rochelle salt (RS), potassium nitrate (PN), sodium nitrite(SN) and potassium iodate (PI). The nano-crystals were grown with preferred crystallographic orientations along the longitudinal axis of the pores under specific thermodynamic conditions. The issues of a preferred site for nucleation and a preferred growth orientation inside the pores will be discussed. The nano-crystals grown inside the pores exhibit a highly sensitive pyroelectric and piezoelectric response characterized by a high figure-of-merit. The pyroelectric response of the TGS crystals to temperature fluctuations and infra-red light modulations is presented. The piezoelectric response of the PI crystals to a modulated applied force is compared to bulk PZT, AlN and ZnO crystals.


CJ-2:L03  Characterization of Nanostructured Phases and Peculiar Phase Transitions in BNBT Lead-free Piezoceramics
L. PARDO, A. GARCÍA, Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), Spain; E. MERCADELLI, C. GALASSI, National Research Council, Institute of Sci. & Technol. for Ceramics, Faenza, Italy

The crystal structure and the electrical properties of BaTiO3(BT), or BiNaTiO3 (BNT) have been studied from the 1950 decade and are now revisited, due to the strong need of development of high piezoelectric sensitivity and lead-free composition materials. Poling remains nowadays as a major issue in the development of high performance lead-free piezoceramics, since it has showed a completely different physical mechanism in these materials. For some of these lead-free compositions, field-induced structural transitions from pseudo-cubic phases to ferropiezoelectrically active phases have been observed [1,2]. Morphotropic Phase Boundaries (MPB) in the solid solutions of these systems have an evolving nature with the electric field [3]. Since the thermal evolution also involves structural changes, depolarization phenomena in these materials are also observed before the ferro-paraelectric temperature that determines the maxima of the dielectric permittivity [3]. Results on ceramics with composition in the solid solution system (1-x)BNT-xBT at the MPB [1] are here shown.
[1] L. Pardo et al. Smart Materials and Structures 19(11), 11507 (2010)
[2] L. Pardo et al. IEEE Trans. UFFC 58(9), 1893-1904 (2011)
[3] L.E. Fuentes et al. Contribution C-20. Proc. X RNE, Madrid (2011)


CJ-2:L04  Photoluminescence, Ferroelectric, Dielectric and Piezoelectric Properties of Sol-gel-derived Er-doped KNN-LN Lead-free Multifunctional Ceramics
XIAO WU, CHI MAN LAU, K.W. KWOK, Department of Applied Physics and Materials Research Centre, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China

A sol-gel method has been utilized to prepare lead-free 2 mol% Er-doped K0.5Na0.5NbO3-xLiNbO3 (Er-KNN-xLN, x = 0.08 and 0.10) ceramics. The XRD results show that the ceramics have the perovskite structure and Er3+ ions have diffused into the host lattice. Compared to the solid-state reaction method, the sol-gel method is favor to reduce the sintering temperatures (~ 50 ℃) of ceramics. Better compositional homogeneity, as well as finer and uniform grains is resulted from the sol-gel process, which have been confirmed by the SEM images. The photoluminescence properties of ceramic bulks have been systemically studied. Under the excitation of 980 nm, the ceramics exhibit visible up-conversion green (510-570 nm) and red (640-685 nm) emissions. The emission colors of them are located in the yellowish green region. The down-conversion emissions in near-infrared (1450-1650 nm) and mid-infrared (2600-2870 nm) regions have been exhibited. The ferroelectric, dielectric and piezoelectric properties of ceramics have also been investigated. Because of the good electrical and excellent photoluminescence performances, our sol-gel-derived Er-doped KNN-LN ceramics should have great potential for multifunctional optoelectronic applications, such as optical-electro integrated materials and devices.


CJ-2:L05  Electromechanical Properties and Microstructure of Undoped K0.5Na0.5NbO3 Ceramics and KNbO3-NaNbO3 Crystals
M. BAH, F. GIOVANNELLI, G. FEUILLARD, I. MONOT-LAFFEZ, Université François Rabelais de Tours, CNRS, CEA, ENIVL, GREMAN UMR 7347, Blois Cedex, France; Laboratoire des Sciences des Procédés et des Matériaux, CNRS, LSPM - UPR 3407, Université Paris 13, Sorbonne Paris Cité, Villetaneuse, France; E. LE CLEZIO, Université de Montpellier 2, IES, UMR 5214, Montpellier, France

PZT and its derivatives exhibit a wide range of piezoelectric properties allowing their applications in transducers, actuators and sensors. However, they are hazardous substances due to the toxicity of lead for human health and environment. Owing to their high dielectric, piezoelectric and mechanical characteristics, (K,Na)NbO3 (KNN)-based solid solutions are promising candidates for lead-free piezoelectric materials (Y. Saito et al., Nature 2004).In the present work, undoped K0.5Na0.5NbO3 ceramics are sintered with the spark plasma sintering technique. The electromechanical properties are related to the microstructure, oxygen stoichiometry and grain size. High thickness coupling factor of 45% and planar coupling coefficient of 48% are reached. The crystal growth of KNbO3-NaNbO3 system is investigated in order to study the effect of grain boundaries and grain size on the properties. This work focuses on the behavior at high temperature and on the stability of the molten zone. The stationary growth conditions of this system are quested by using the original floating zone method. The resulting crystals are characterized and Laue diffraction is performed on extracted samples.
The piezoelectric properties of these crystals are compared to those of their homologous ceramics.


CJ-2:IL06  Tuning the Chemistry and Architecture of Ferroelectric Thin Films and Multilayers for On-silicon Integration
D. LEVASSEUR^{1, 2}, E. BOUYSSOU², R. DE PAOLIS³, A. ROUSSEAU¹, F. COCCETTI³, G. GUEGAN², S. PAYAN¹, M. MAGLIONE¹, ¹CNRS, Univ. Bordeaux, ICMCB, UPR 9048, Pessac, France; ²ST Microelectronics, Tours, France; ³CNRS, Univ. Toulouse, LAAS, Toulouse, France

Ferroelectric thin films are under investigation for their possible use as tunable components for telecoms. The main limitations of these films are their high frequency losses and leakage current. We first addressed this issue on inserting a low loss dielectric barrier like SiO2 between the active film and its electrodes [1]. While being attractive at low frequencies, this solution was not efficient in the targeted telecom GHz frequency range. More recently, we have tuned the chemistry of (Ba,Sr)TiO3 to reduce the leakage current. Substituting Manganese on the Titanium site as was done previously in ceramics, we were able to reduce the leakage current. In depth XPS and optical elipsometry allowed us to ascribe this strong improvement to the trapping of electronic charges on deep levels in the band gap. The full modeling of such lowering of the leakage current will be described [2].
[1] V. Reymond, D. Michau, S. Payan, and M. Maglione J.Phys.: Condensed Matter 16, 9155 (2004)
[2] D. Levasseur, E. Bouyssou, R. De Paolis, A. Rousseau, F. Coccetti, G. Guegan, S. Payan, M. Maglione, J.Phys.Condensed Matter 2013 (in press)


CJ-2:IL07  Ferroelectrics for Wireless Sensor and Transducer Applications
KUI YAO, CHIN YAW TAN, SZU CHENG LAI, LEI ZHANG, ZHIYUAN SHEN, YIFAN CHEN, Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), Singapore

Many functions in ferroelectric materials involving energy conversions are attractive for sensor, transducer, and energy harvesting applications. Moreover, as dielectric materials with large polarization, ferroelectric materials also exhibit great values to directly store electrical signal and energy. Combining the effects of sensing and energy harvesting, and sometimes even the charge storage function, can potentially lead to advanced energy autonomous and wireless devices based on ferroelectric materials. With the power reduction in electronics, particularly in RF transmissions, many wireless sensors and transducers enabled with the material functions in ferroelectric materials may be becoming technically realistic and commercially viable in the future. Technical analyses on these characteristics of ferroelectrics valuable for wireless sensors and transducers will be conducted in this talk. Research activities on several technical developments involving ferroelectric materials and their applications for energy autonomous and wireless sensors and transducers in our lab are discussed.


CJ-2:L08  Characterization of Material Properties and Functionalities of Lead-free Bismuth-based Ceramics
L. BATISTA, U. RABE, S. HIRSEKORN, Fraunhofer Institute for Nondestructive Testing (IZFP), Saarbrücken, Germany

Ferroelectric materials are widely used in many applications as sensors, actuators, transducers, etc. Most of these materials are however based on toxic elements, as e.g. Lead (Pb), which can create hazards during materials processing, and also disposal. With the new European regulations restricting the use of such toxic elements, the need arises for new materials which provide the same or better functional properties. These properties such as piezoelectric constants and high electromechanical coupling factors are mostly determined by the microstructure and the arrangement of the domains. In the framework of a European/Mexico Project (BisNano), lead-free Bismuth-based bulk ceramics like (BNT), (BNT-BT), Mn-doped BNT-BT and Sr-doped BNT-BT were investigated and evaluated by different operating modes of an atomic force microscopy (AFM), especially dynamic modes in the ultrasonic range like the ultrasonic piezoelectric force microscopy (UPFM). Macroscopic properties of the above mentioned lead-free bismuth-based samples were also examined. Their piezoelectric activity was characterized by impedance and 3D laser vibrometer measurements. Mechanical properties such as Young's and shear moduli were determined by measuring longitudinal and transverse wave velocities and the density.


CJ-2:IL10  How can be Realized High Piezoelectricity from Measuring Acoustic Wave Velocities?
T. OGAWA, Department of Electrical and Electronic Engineering, Shizuoka Institute of Science and Technology, Fukuroi, Japan

Material research on piezoelectric ceramics was proposed from viewpoints of relationships between piezoelectricity and elastic constants such as Young's modulus (YE) and Passion's ratio (σ). We had investigated the relationship with k31 (coupling factor of transverse vibration mode) vs YE on various kinds of single crystals and ceramics. There was a linear relationship with k31 vs YE. Therefore, it was confirmed that the origin of high piezoelectricity was due to the mechanical softness of the materials. We developed a method to be convenient to measure acoustic wave velocities suitable for disk samples (dimensions of 10-15 mm diameter and 1.0-1.5 mm thickness) by an ultrasonic thickness gauge (Olympus Co., Model 35DL) with high-frequency (30 MHz and 20 MHz) pulse oscillation. From the relationships between kp (planar coupling factor of disk) vs longitudinal (VL) and transverse wave velocities (VS), Y33E and σ in PZT, PbTiO3, alkali niobate and alkali bismuth titanate, it was possible to divide VL and VS into three material groups. The kp lineally increased from 4 to 65% with decreasing Y33E from 15×1010 to 6×1010 N/m2 and lineally increased with increasing σ from 0.25 to 0.43. It was clarified that higher kp values can be realized at lower Y33E and higher σ values.


CJ-2:L12  Distinctive Contributions to High-temperature Dielectric Response of Relaxor Ferroelectric Lead Scandium Niobate Ceramic System
V. BOBNAR, H. URSIC, G. CASAR, S. DRNOVSEK, Jozef Stefan Institute, Ljubljana, Slovenia

Dielectric properties of Pb(Sc1/2Nb1/2)O3 ceramics, prepared from mechanochemically activated powder and showing a high degree of chemical homogeneity, were studied in a broad temperature range of 150-775 K. Various contributions were recognized in the detected response. A typical relaxor dispersive maximum, accompanied by a sharp hysteretic dielectric anomaly reveals that developed disordered PSN system even in zero electric field undergoes a spontaneous relaxor-to-ferroelectric phase transition. At high temperatures, a strong dielectric dispersion due to the Maxwell-Wagner-type surface-layer contributions governs the detected response. The intrinsic high-temperature response follows, however, the universal scaling rather than the classical mean-field behavior. The latter can be rejected on a confidence level better than 99%, and the analysis revealed a critical exponent indicating a behavior typically found in spin glasses. Finally, a perfect agreement between the fitting parameter of Tc=372 K (obtained by analysis in the interval of 600-775 K) and the experimentally detected value of this relaxor-to-ferroelectric transition temperature manifests that the low-temperature fingerprint behavior can be observed at much higher temperatures, well above the dispersive relaxor maximum.


CJ-2:L13  Effect of Isovalent B-site Doping on Structural and Electrical Properties of Bismuth-Sodium-Titanate
K. REICHMANN, M. NADERER, J. ALBERING, Christian Doppler Laboratory for Advanced Ferroic Oxides, Graz University of Technology, Graz, Austria; F.A. MAUTNER, Institute of Physical and Theoretical Chemistry, Graz University of Technology, Graz, Austria

Bismuth Sodium Titanate is the base compound for a family of lead-free piezoelectric materials, because of its extraordinary large strain induced by the electric field. With increasing temperature the ferroelectric phase turns into a non-polar relaxor phase at about 190°C and into a paraelectric phase above 350°C. Many modifications, including donor and acceptor doping on B-site, alkaline earth and rare earth doping on A-site and solid solutions with other ferroelectric perovskite compounds have been studied with respect to phase transitions, ferroelectric and piezoelectric properties.
This study investigates the effects of isovalent B-site doping by substituting tetravalent Titanium by the larger Zirconium and Tin and the smaller Germanium. Zirconium and Tin have a similar ionic radius but differ in mass and electronic structure. Tin and Germanium have the same electronic structure but differ in ionic radius (larger and smaller respectively than Titanium).
The samples were examined by X-ray diffraction, scanning electron microscopy, temperature dependent dielectric measurements and large signal polarization and strain measurements. The differences in symmetry, microstructure, dielectric and piezoelectric properties are outlined.


Session CJ-3 - Multiferroics

CJ-3:IL01  Hybrid Multiferroic Heterostructures
N.A. PERTSEV, A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences, St. Petersburg, Russia

In this Invited Lecture, recent advances in theoretical and experimental studies of multiferroic hybrids and heterostructures are reviewed. The first part is devoted to strain-mediated magnetoelectric (ME) effects appearing in ferroelectric-ferromagnetic (FE-FM) hybrids owing to the mechanical coupling between constituents. According to the theoretical predictions, strong enhancement of the direct ME effect should take place near strain-driven phase transitions in FE thin f ilms deposited of FM substrates. In turn, the converse ME effect maximizes in hybrids comprising FM films grown on relaxor ferroelectrics, and a giant ME susceptibility is expected near spin reorientation transitions. Remarkably, a magnetic tunnel junction fabricated on a FE substrate represents an electric-write nonvolatile magnetic memory cell with nondestructive readout. In the second part, interface-related ME phenomena in ferroic nanostructures are discussed. In particular, we consider the interfacial ME effect resulting from changes in the band structure at FM-FE interfaces, which leads to the appearance of four resistance states in multiferroic tunnel junctions. Finally, the voltage-driven magnetization dynamics in nanostructures with the electric-field-dependent interfacial anisotropy is described.


CJ-3:IL02  Optical Probing of Ferroelectrics and Multiferroics
V. GOPALAN, Materials Science and Engineering, Pennsylvania State University, University Park, PA, USA; T. LUMMEN, EPFL, Lausanne, Switzerland

Ferroelectric materials possess a built-in electrical polarization in the material in the absence of any external field, and a field can switch between distinct polarization states.  Multiferroics may in addition be (anti)ferromagnetic and ferroelastic.  In this talk, I will present optical probing of ferroelectric, ferroelastic and magnetic phenomena using linear and nonlinear optics.
First, in classic ferroelectrics such as barium titanate and potassium niobate, we have discovered a new low symmetry monoclinic phase with piezoelectric and nonlinear optical properties that are 400% higher than the known phases.  These metastable phases are stabilized across the known first order ferroelectric-ferroelectric phase transitions in the presence of domain walls, giving them what I term a “thermotropic phase boundary” character.
Secondly, in a nonpolar distorted perovskite such as CaTiO3, I will demonstrate the presence of polar domains through a roto-flexo effect, i.e a coupling of rotostriction and flexoelectricity.
Finally, I will present examples of multiferroics, such as BiFeO3 and EuTiO3 where the multiferroic character is revealed with optics in combination with other techniques.


CJ-3:IL03  Polarization Fatigue and Non-destructive Readout of Ferroelectric Memory
XI ZOU, RUI GUO, LU YOU, JUNLING WANG, School of Materials Science and Engineering Nanyang Technological University, Singapore

Ferroelectric fatigue refers the reduction of switchable polarization upon repetitive electrical cycling. It is detrimental to the performance and life time of ferroelectric base devices, and has been studied for decades.[1] Different mechanisms have been proposed, including defects redistribution and charge injec-tion. However, direct microscopic study of fatigue has yet to be explored. We have studied the fatigue of BiFeO3 films using PFM and SKPM under a planar-electrode setup. [2] It is observed that negative charges accumulate (e.g. electrons) at the electrode/film interface during fatigue measurement, where domain pinning occurred. When the pinned domains grew across the channel after further cycling, macroscopic fatigue was observed. To circumvent the fatigue problem, non-destructive readout of fer-roelectric memory needs to be developed. I will also discuss our recent work on ferroelectric photovol-taic effect for memory application. [3]
References
[1] N. Setter et al, J. Appl. Phys. 100, 051606 (2006).
[2] Xi Zou, Lu You, Weigang Chen, Hui Ding, Di Wu, Lang Chen, and Junling Wang, ACS Nano, 6, 8997 (2011).
[3] Rui Guo, Lu You, Yang Zhou, Zhi Shiuh Lim, Xi Zou, Lang Chen, R. Ramesh, Junling Wang, Nature Communication, 4:1990 doi: 10.1038/ncomms2990 (2013).


CJ-3:IL05  Doping Driven Control of the Concomitant Ferroelectric and Magnetic Transition in Bismuth Ferrites
CHAN-HO YANG, Department of Physics, KAIST; and KAIST Institute for the NanoCentury, Daejeon, Republic of Korea

The antiferromagnetic transition temperature of the highly-elongated bismuth ferrite is largely suppressed to near room temperature and moreover the ferroelectric order undergoes a first order transition to another ferroelectric state simultaneously at the magnetic transition temperature indicating strong spin-lattice coupling [1]. The c-axis lattice parameter change at the magnetic transition temperature is ~0.2 % which is comparable with current commercialized magnetostrictive alloys like Terfenol-D. Our findings reveal a unique example of concurrent magnetic and ferroelectric transition at the same temperature in a proper ferroelectric, potentially providing an avenue for room temperature magnetoelectric applications. In the talk, our strategy to modify the multiferroic transition through chemical substitutions will be introduced.
[1] K. T. Ko et al., Nature Communications 2, 567 (2011)


CJ-3:IL06  Metal-organic Chemical Vapor Deposition of Magnetoelectric BiFeO3 based Multiferroics: Nanocomposites and Solid Solutions
G. MALANDRINO, Dipartimento di Scienze Chimiche, Università di Catania, and INSTM UdR Catania, Catania, Italy

Multiferroics, are materials in which at least two of the three ferroic orders, ferroelectricity, ferro- or anti-ferromagnetism and ferroelasticity coexist. Nevertheless, they do not usually exhibit the magnetoelectric effect and to produce challenging magnetoelectric devices, i.e. to manipulate magnetization by an electric field at room-temperature, the fabrication of magnetoelectric materials represents a crucial step. BiFeO3 is unique among various multiferroics, as its ferroelectric and magnetic transition temperatures are well above the room temperature, thus it represent a key material in the fabrication of magnetoelectric systems. In the present study MOCVD has been exploited as a synthetic route to produce nanocomposite and/or solid solution thin films. In particular, fabrication of Bi(1-x)AxFe(1-y)ByO3 films or BiFeO3/AxByOz (A = Ba, Co; B = Ti, Fe) nanocomposites on insulating and conducting perovskite substrates will be addressed. Film structural, morphological and compositional characterizations provided a suitable correlation between properties of mixed films and deposition conditions. Ferroelectric/piezoelectric properties have been investigated at the nanoscale level by Piezoresponce Force Microscopy (PFM) and Single-point Piezoresponce Force Spectroscopy (SPF).

 
Session CJ-4 - Semiconducting Ceramics

CJ-4:IL01  Thermoelectric Properties of TiO2 Based Materials: Review with Recent Developments
J. LOCS, K. RUBENIS, Riga Technical University, Rudolfs Cimdins Riga Biomaterials Innovations and Development Centre, Riga, Latvia

Transitional metal oxides have attracted significant attention in recent years and are considered as promising alternative materials for thermoelectric applications, since they are environmental friendly and have high chemical and thermal stability at high temperatures. Although titanium dioxide is one of the most studied transition metal oxides, in the field of thermoelecric materials it is relatively less investigated. In this presentation we review current progress of titanium dioxide based thermoelectric materials. The effect of structural defects, various dopants, synthesis methods, processing techniques and conditions on electrical, thermal and themroelectric properties of TiO2 will be reviewed.


CJ-4:IL03  Spatially Resolved Photo-detection in Leaky Ferroelectric Oxides
MOO-HO JO, Center for Artificial Low-Dimensional Electronic Systems (Institute for Basic Science, IBS) & Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Korea

Spontaneous polarization in ferroelectrics is electrically switchable in a hysteretic manner and thus serves as a basis for solid-state memory. It can also yield interesting optoelectronic memory effects as an active channel upon photogenerated carrier motions, whose spatial variation can be inherently determined over the internal potential gradient, imposed by ferroelectric domains and domain walls at the nanometer scale. Here, we provide visual evidence for such optoelectronic memory characteristics, spatio-temporally resolved on mono-domain and multi-domain ferroelectric BiFeO3 thin films. Specifically, it was found that the local internal order of spontaneous polarization at the ferroelectric domain and oxygen vacancy migration at the domain walls independently determine the optoelectronic switching characteristics. Our study suggests implication for non-volatile optoelectronic memory based on ferrroelectric oxides by domain engineering and nano-ionic transport.


CJ-4:IL05  P-type Oxide Semiconductors for High Performance Gas Sensors: New Challenges and Opportunities
JONG-HEUN LEE, Department of Materials Science and Engineering, Korea University, Seoul, Republic of Korea

Oxide semiconductors are promising material platforms for highly sensitive, cost-effective, and reliable gas sensors. Since 1960s, the n-type oxide semiconductors such as SnO2, ZnO, TiO2, In2O3, Fe2O3, and WO3 have been intensively studied to detect trace concentrations of harmful, toxic and explosive gases. In contrast, the p-type oxide semiconductors such as NiO, CuO, Cr2O3, and Mn3O4 with different receptor functions, conduction paths, and gas sensing mechanisms, have been barely investigated as chemoresistive materials because of their relatively low gas responses. Moreover, the selective detection of a specific gas using oxide semiconductors remains a challenging issue for the practical applications. In this contribution, new strategies to design high-performance p-type oxide semiconductors with ultrahigh sensitivity and ultrahigh selectivity have been suggested, which include the control of charge carrier concentration by aliovalent doping and the promotion of sensing reaction toward a specific gas by loading or doping catalysts. The p-type oxide semiconductors with distinctive catalytic activity and electrical property are valuable materials to design gas sensors with new and novel functionalities.


CJ-4:IL06  Properties of n-type CeO2 and its Gas Sensor Application
N. IZU, National Institute of Advanced Industrial Science and Technology (AIST), Nagoya, Aichi, Japan

CeO2 (cerium oxide or ceria) is attractive to many applications. This paper focuses on gas sensors using ceria.
Ceria is one of nonstoichiometric oxides and can change its oxidation state from Ce3+ to Ce4+ and vice versa. The principle of resistive type ceria gas sensor is as follows: When oxygen concentration decreases, the equilibrium shifts and Ce3+ (CeCe') and VO.. increase on the surface of cerium oxide. Then CeCe' and VO.. diffuse to inside. Finally the equilibrium is achieved. Since the charge carrier is CeCe' in cerium oxide, the electrical conductivity of cerium oxide increases. Here the diffusion coefficient of VO.. is much smaller than that of CeCe'. Therefore, the surface reaction and the VO.. diffusion are very important when we consider the rate-limiting step of the sensor response.
In this paper, resistive type sensors using ceria are introduced: Oxygen sensors with fast response properties, oxygen sensors with temperature independent signal, carbon monoxide sensors made from nanoparticles with very unique structures and so on.


CJ-4:L07  Nano-derived Tungstate and Molybdate Oxides for the Sensing of H2, H2S and SO2 at High Temperatures
E.M. SABOLSKY, E. CIFTYUREK, K. SABOLSKY, Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV, USA

The measurement of H2, H2S and SO2 concentrations within coal gasifiers and other reactors is important for process control and emissions monitoring. The development of selective sensing materials that will be active at high temperature (>500 C) for these gasses has shown to be a challenge. The high temperature conditions usually result in compositional and microstructural instability due the increased kinetics for sintering/coarsening and chemical reactions. The current work investigates the use of ternary tungstate and molybdate nanomaterials as sensing materials for these gases at 600-1000 C. The electrical response (chemiresistive response) towards H2, H2S and SO2 at levels of 5 to 4000 ppm in N2 and microstructural stability were investigated. The sensing nanomaterials were deposited over interdigitized electrodes to form both a centimeter- and micron-size sensor platform. The microstructural, compositional and electrical analyses were completed over untested and tested sensors, and a basic mechanistic model was developed to explain the highly selective nature and stability of the various sensing compositions.


CJ-4:L08  High Crystalline Cu2O Thin Films Prepared by Electric Current Heating Using Copper Wire
T. OKAMOTO,  K. YAMAZAKI, Y. KUROKI, Nagaoka University of Technology, Nagaoka, Niigata, Japan; M. TAKATA, Japan Fine Ceramics Center, Atsuta-ku, Nagoya, Japan, Nagaoka University of Technology, Nagaoka, Niigata, Japan

Cuprous oxide (Cu2O), which is a non-toxic and inexpensive p-type semiconductor with a direct band gap of 2.1 eV, is expected to be used for many electrical and optical applications such as photovoltaics, gas sensors, photocatalysts, spintronics and storage devices. However, it is difficult to obtain the single phase of Cu2O with a high crystallinity. In most cases, mixture of phases of Cu, Cu2O and CuO is obtained and post-annealing or etching process to remove the phases excepting Cu2O is necessary. The difficulty to obtain the single phase of the Cu2O is one of the nagging problems for utilizing Cu2O as a semiconductor. In this study, Cu wires were heated by the electric currents to prepare Cu2O thin films. The films with Cu2O single phase were successfully deposited on glass substrates placed above the wires under air pressures in the range of 100 - 40 Pa. Annealing at 800 oC under atmospheric pressure with oxygen partial pressure of 12 Pa greatly improved its crystallinity, and the films showed the improved time response for photoconductivity.

 
Session CJ-5 - Fast Ion-conducting Ceramics

CJ-5:IL01  Advanced Composite Electrodes for Solid State Li-ion Battery
K. KANAMURA, M. SHOJI, J. WAKASUGI, H. MUNAKATA, Department of Applied Chemistry, Tokyo Metropolitan University, Hachioji, Tokyo, Japan

All solid state battery has been investigated for next generation electrochemical energy storage system. Several Li+ ion conductive solid electrolyte have been applied to this battery. There are two kinds of ceramics for all solid state battery. One is sulfide and another is oxide. In both case, a composite between active material and solid electrolyte have to be prepared in order to produce a good interface between them. In this report, the fabrication and characterization for the composite with solid oxide electrolyte is presented to show solved problems for realization of all solid electrolyte. An electrochemical reaction rate of composite between active material and solid electrolyte is determined by a contact area and interfacial chemical and physical properties. In this study. Li7La3Zr2O12 (LLZ) was utilized as solid electrolyte and LiCoO2 (LCO) was used as active material. Three dimensional hole-array structure of LLZ was prepared by using photolithography to obtain larger contact area between LLZ and LCO. In addition, in order to control chemical and physical properties of interface between LLZ and LCO, the sol-gel process was employed. The discharge and charge characteristics of the prepared cell was tested using electrochemical methods.


CJ-5:IL02  New Interstitial Oxide Ion Conductors for Electrochemical Applications
S. SKINNER, R. BAYLISS, C. HARRIS, CHENG LI, Imperial College London, London, UK; M. LAGUNA-BERCERO, Univ. Zaragoza, Spain

Interstitial oxides have been gaining interest as potential fast ion conductors for fuel cell and electrolyser applications. New materials with crystallographic supercells are discussed here with details of the variation of conductivity with rare earth substitution in the LnNbO4+d series of oxide electrolytes. Preliminary data on the electrochemical performance of these materials in both fuel cell and electrolyser modes will be discussed. In detail, the correlation of the crystallographic superstructure, its transformation to a simple tetragonal cell and the associated changes in conduction will be addressed.


CJ-5:L04  Modelling of the Oxygen Transport through MIEC Membrane for the Transient Stage
C. GAZEAU, E. BLOND, Univ. Orléans, PRISME EA 4229, Orléans, France; M. REICHMANN, P.-M. GEFFROY, T. CHARTIER, SPCTS, UMR CNRS 7315, Limoges, France; N. RICHET, Air Liquide CRCD, Jouy En Josas, France

Mixed Ionic and Electronic Conductors are promising membrane materials for oxygen separating from air at high temperature.The oxygen semi-permeation induces a "chemical" expansion in the same order as the thermal expansion[1].Mechanically, the transient stage is critical due to the stress induced by the chemical and thermal strain[2].To predict this strain, the oxygen activity field through the membrane needs to be known.Usually the membrane is divided into three zones: the bulk where diffusion takes place and the two surfaces where exchanges between atmosphere and membrane take place.Oxygen bulk diffusion is well described by the Wagner theory[3].A consensus has not yet emerged regarding the surface exchange models proposed in the literature.Moreover, these models describe the permanent state, and cannot be extended to the transient stage.This presentation proposed a new macroscopic surface exchange model for transient stage.This model supposed that the oxygen flux is governed by the association/dissociation of adsorbed oxygen and by the high energetic cost of oxygen reduction/oxidation.Then, the balance of transient species is introduced to account for these two phenomena.
[1]Pei,Catal. Lett,(30),1995
[2]Valentin,Adv Sci Tech,(65),2010
[3]Wagner,Prog Solid State Ch,(10),1975


CJ-5:L05  Thermal Residual Stress and Biaxial Strength of (Y2O3)0.08(ZrO2)0.92 / (Sc2O3)0.1(CeO2)0.01(ZrO2)0.89 Multi-layered Electrolytes for Intermediate Temperature Solid Oxide Fuel Cells
YAN CHEN^{1, 2}, A. AMAN¹, M. LUGOVY^{1, 3}, N. ORLOVSKAYA¹, XINYU HUANG⁴, T. GRAULE⁵, J. KUEBLER⁵, ¹Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, FL, USA,  ²Chemical and Engineering Materials Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA; ³Institute for Problems of Materials Science, Kyiv, Ukraine; ⁴University of South Carolina, Columbia, SC, USA; ⁵Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for High Performance Ceramics, Duebendorf, Switzerland

8 mol % Y₂O₃-ZrO₂ [YSZ] has been widely used as electrolyte material in SOFCs. (Sc₂O₃)_0.1(CeO₂)_0.01(ZrO₂)_0.89 [SCSZ] has higher ionic conductivity in the intermediate temperature range (600 °C - 800 °C) compared to YSZ, but YSZ has better chemical and phase stability. In this work YSZ and SCSZ were used in developing layered electrolytes with a unique design to incorporate both materials, resulting in an electrolyte with enhanced ionic conductivity and improved robustness. The design involved placing SCSZ layers between two outer YSZ layers, so as to produce four- and six-layered electrolytes. Tape casting, lamination and presureles sintering techniques were used in the development of the electrolytes. Due to the mismatch of the coefficient of thermal expansion between the two materials, thermal residual stresses arise between the layers. These stresses contribute to an enhancement of the ionic conductivity of the layered electrolytes. In addition to improvement of electrochemical performance the compressive residual stress effects significantly mechanical properties of layered electrolytes. Biaxial flexure strength was measured using ring-on-ring strength testing at room temperature and 800 °C. A finite element method was employed to calculate the maximum principal stress at fracture. The results showed that the layered YSZ/SCSZ/YSZ electrolytes have improved flexure strength at both room temperature and 800 °C because of the appearance of compressive residual stresses in the outer YSZ layers of the electrolyte. The calculated compressive stress values were also verified using Weibull statistics of strength data measured at room temperature.  


CJ-5:IL06  Electrical Conductivity on Novel Solid Electrolytes based on Scandia-stabilized Zirconia
R.L. GROSSO, E.N.S. MUCCILLO, Energy and Nuclear Research Institute, S. Paulo, SP, Brazil

Scandia-stabilized zirconia (SSZ) is a well-known solid electrolyte with high oxide-ion conductivity and potential application in solid oxide fuel cells operating at intermediate temperatures. The ionic conductivity is maximized for scandia contents near the phase boundary between the single cubic and the mixed tetragonal and cubic fields (~ 9 mol%). The main concern related to this system is the formation of the low-conducting rhombohedric phase for scandia contents at and above that of maximum ionic conductivity. In recent years, there has been a growing interest in this solid electrolyte, mainly due to the encouraging results on stabilization of the cubic phase through the strategy of introduction of a second additive. In this work, recent results on structural and electrical properties obtained with several additives including single and multivalent cations in SSZ are reported. Small amounts of these additives have shown to stabilize, to some extent, the cubic phase in SSZ at room temperature. The electrical conductivity reveals similar behavior for all investigated compositions, although the magnitude of the ionic conductivity is lower for systems containing additives.


CJ-5:IL07  Efficient Search of Fast Lithium Ionic Conductors Through Ab Initio-based Computational Methods and Material Informatics
M. NAKAYAMA^1-3, R. JALEM², ¹Department of Materials Science & Engineerings, Nagoya Institute of Technology, Japan; ²JST-PRESTO program, Japan; ³ESICB project, Kyoto-University, Japan

Olivine-type LiMXO4 composition (main group M2+-X5+, M3+-M4+ pairs) of ordered structure was successfully investigated as a potential solid electrolyte using Li-ion jump energy (EA) consideration through a combination of first principles calculation and partial least squares (PLS) method. We found out that M ionic size and its associated octahedron distortion contributed most significantly to EA value. The results showed promising MX pairs (<0.30 eV) such as MgAs, ScGe, InGe and MgP among compositions with experimental data, and Group 13 (Al, Ga, In)-X pairs and M-Sn pairs among potential novel materials.


CJ-5:IL08  Proton Migration at Grain Boundary of Barium Zirconate and Cerate: Space Charge Layer and Structural Disorder Models
J.-H. YANG, J.-S. KIM, YEONG-CHEOL KIM, Korea University of Technology and Education, Cheonan, Korea; B.-K. KIM, Korea Institute of Science and Technology, Seoul, Korea

Acceptor-doped barium zirconate and barium cerate are the promising candidates as solid electrolytes for protonic ceramic fuel cells. Yttrium-doped barium zirconate shows sound chemical stability and excellent proton conductivity at the bulk while its proton conductivity at grain boundaries is poor due to existence of resistive grain boundaries in polycrystalline samples. Contrary to yttrium-doped barium zirconate, yttrium-doped barium cerate shows poor chemical stability but relatively good proton conductivity at both grain boundaries and the bulk. In order to evaluate differences between their grain boundary properties, the Σ3 tilt grain boundaries in barium zirconate and cerate were investigated by using density functional theory. Low proton conductivity at grain boundaries can be evaluated via the space charge layer model and structural disorder model.


CJ-5:L09  Evaluating Oxygen Diffusion and Surface Exchange Coefficients in La0.5A0.5Fe0.7Co0.3O3-d (with A= Ca, Sr and Ba) Perovskite Membranes by Oxygen Semi-permeation Measurements
M. REICHMANN, French Environment and Energy Management Agency, Angers, France; P.M. GEFFROY, T. CHARTIER, Laboratoire Science des Procédés Céramiques et de Traitements de Surface, Limoges, France; N. RICHET, Air Liquide, Centre de Recherche Claude-Delorme, Jouy-en-Josas, France

Numerous perovskite materials are reported as promising materials for Oxygen Transport Membranes. However, the impact of oxygen bulk diffusion and surfaces exchanges on oxygen flux through the membrane is not clearly evaluated in relation with the membrane materials and working conditions.
To identify the rate determining step, a new criterion, Bc defined by the ratio between the drop of the oxygen chemical potential at the surface and the drop of the oxygen chemical potential through the bulk of the membrane, is suggested.
The oxygen chemical potential through the membrane is measured thanks to a specific apparatus. Oxygen activities on the membrane surfaces are measured during the semi-permeation flux measurement with tips in contact with the surfaces of the membrane. The determination of the oxygen chemical potential at the surface of the membrane is possible using the Nernst law. These measurements also allow the evaluation of surface exchanges kinetic coefficients on rich and lean oxygen face, and of the coefficient of diffusion.
The aim of this study is to establish a correlation between the nature of substitution cation (A) in cobaltite perovskite materials, La0.5A0.5Fe0.7Co0.3O3-d (with A= Ca, Sr and Ba) and oxygen diffusion rate or surface exchange kinetic coefficients.


Poster Presentations

CJ:P01  Fabrication and Characterization of (K0.5Na0.5)NbO3-CaZrO3 Lead-Free Piezoelectric Ceramics
MYOUNG PYO CHUN, H.S. SHIN, B.I. KIM, Korea Institute of Ceramic Engineering and Technology (KICET), Seoul, Rep.of Korea

In recent years, studies on lead-free piezoelectric ceramics have been increased in view of environmental aspects. (1-x)(K0.5Na0.5)NbO3-xCaZrO3 (herein after as KNN-CZ, x=0, 2 and 4 mol%) ceramics were synthesized by a conventional solid state method. Their microstructure, crystal structure, and piezoelectric properties were investigated with SEM, X-ray diffraction (XRD), Raman spectroscopy, and d33 meter. The subcell of (1-x)KNN-xCZ (x=0, 2 and 4 mol%) has the monoclinic symmetry without respect to its chemical composition. Lattice parameters of the perovskite subcell a, b, and c as well as angle β were calculated from (200), (020), (022), (024) and (224) diffraction peaks based on a monoclinic subcell. With increasing CaZrO3 doping amount, the lattice parameters a and c decrease monotonically but the lattice parameter b and monoclinic angle β show the maximum and minimum at x = 2 mol% respectively, which corresponds to a peak of wave number of the υ1 stretching mode. A piezoelectric constant of d33 = 121 pC/N was obtained at x = 2 mol%, which is likely to suggest the possible phase transition at x = 2 mol%.


CJ:P02  Microstructure and Dielectric Properties of Ba-rich BaTiO3 Doped with MgO and Y2O3
CHE-YUAN CHANG, YUN-SHIUAN HOU, CHI-YUEN HUANG, Department of Resources Engineering, National Cheng Kung University, Tainan City, Taiwan

Microstructure and dielectric properties of Ba-rich BaTiO3 (Ba/Ti = 1.005) doped with MgO (0.5 and 1.0 mole%) and/or Y2O3 (1.0, 3.0, and 5 mole%) were investigated. Doping either MgO or Y2O3 can enhance sintering shrinkage and inhibit grain growth of BaTiO3, separately. However, the sintering shrinkage was suppressed when doping more Y2O3 (3.0 mole%). When doping MgO and Y2O3 together, the relative density can reach 90% at a sintering temperature of 1300 °C/3h, and the grain size were from 1.0 to 2.0 μm and increases with lower Mg/Y doping ratio. Doping more MgO can lower tetragonality, and the core-shell structure can be obtained when co-doping MgO and Y2O3 and sintering at 1300 °C for 3 h. Doping MgO also flattened the temperature-capacitance curve (TCC) with lower Curie temperature. There was slight change of the TCC curve when doping 1.0 and 3.0 mole% Y2O3, and a flat TCC curve when doping 5.0 mole% Y2O3.


CJ:P04  The Effects of the Annealing Conditions on the Dielectric Properties of the Sol-gel Derived MgNb2O6 Thin Films
YI-DA HO, KUNG-RONG CHEN, CHENG-LIANG HUANG, Department of Electrical Engineering, National Cheng Kung University (NCKU), Tainan, Taiwan

MgNb2O6, a well-known ceramic material with columbite crystal structure, has attracted much attention in microwave integrated circuits and optical applications due to its superior properties, such as its high dielectric constant and an optical band gap. In this work, transparent amorphous-MgNb2O6 thin films were fabricated on ITO/glass substrates using the sol-gel method. The average optical transmission percentage in the visible range (λ=400-800 nm) is over 80% for all MgNb2O6/ITO/glass samples, while the optical band gap is estimated at ~4 eV. On the other hand, the dielectric properties of the MgNb2O6 thin films were very sensitive to the annealing conditions. In this study, the dielectric constant of the films was calculated to be higher than 30 under a 100 kHz AC electric field. The effects of the annealing temperature and atmosphere on the dielectric properties of the MgNb2O6 thin films were investigated.


CJ:P05  PZT Powders Produced from Recycled Ceramics
M.V. GELFUSO, A.C. LANZA, D.THOMAZINI, Universidade Federal de Itajubá-UNIFEI, Itajubá, Brazil

Lead zirconate titanate(PZT) ceramics have been extensively used in various applications related to ultrasonic sensors and actuators. However, a major concern with the use of PZT ceramics is that after the disposal of these ceramics, due to some failure during use, they can contaminate the environment, because there is the presence of lead in their chemical composition. Thus, the recycling of PZT ceramics not only assists in reducing the use of materials of high purity and cost, but also in the preservation of the environment. In this work, PZT powders were obtained from ceramic recycling discarded after breakage in use in ultrasonic-welding devices. It is proposed a method to recycle PZT ceramics based on the coprecipitated chemical method. PZT phase was confirmed from DRX analyses and particles about 190 nm were observed by MEV characterization.


CJ:P07  Investigation of the Domain Switching in the Bulk and on the Surface of Barium Titanate
A. REICHMANN, Austrian Centre for Electron Microscopy and Nanoanalysis, Graz, Austria; S. MITSCHE, A. ZANKEL, P. PÖLT, Institute for Electron Microscopy, Graz University of Technology, Graz, Austria; K. REICHMANN, Christian Doppler Laboratory for Advanced Ferroic Oxides, Graz University of Technology, Graz, Austria

The electrical and mechanical properties of ferroelectrics are governed to a great extent by domain wall motion. Ferroelectric BaTiO3 was mechanically poled in situ in an environmental scanning electron microscope equipped with a tensile stage recording the domain wall motion by orientation contrast imaging. Stress induced domain formation by the polishing procedure can be excluded due to X-ray diffraction measurements.
A grain at the surface of a ceramic body experiences no clamping from the surface and therefore its clamping conditions differ from a grain inside the body and will twin differently. The changes in the domain pattern observed on the surface during the in-situ experiments are compared to domain patterns of the body of the sample after mechanical compression by cutting the same sample into two pieces investigating the freshly polished cross section.
The compression tests were carried out in an ESEM from FEI using the low vacuum mode equipped with a slightly modified tensile stage from Deben (load cell: 1250). Domain wall motion was observed at a stress exceeding 33 MPa resulting in mechanical poling. Preferred orientation of the poled samples was evaluated by x-ray diffraction done with a Siemens D5005 diffractometer.


CJ:P10  Effect of BT Template Size on Piezoelectric Properties of Textured PMN-PT Ceramics
JAESUNG SONG, JUHYEONG JO, MIN-SOO KIM, IN-SUNG KIM, SOON-JONG JEONG, Korea Electrotechnology Research Institute, Changwon, Rep. of Korea

Many studies have been performed on piezoelectric ceramics prepared via the templated grain growth (TGG) process thereafter, which proved that the degree of crystalline orientation in those ceramics was a very effective cause of the improved piezoelectric properties. There are several requirements for the templates to textured ceramics by TGG. The templates have to possess an anisometric morphology to facilitate alignment within the matrix during tape casting. In addition, they should have the desired orientation, a lattice match to the crystal and thermodynamic stability at the process temperature. In this study, textured 0.675Pb(Mg1/3Nb2/3)O3-0.325PbTiO3 (PMN-PT) was manufactured from variously-sized BaTiO3 (BT) templates via TGG. The effect of BT template size was investigated in regard to the degree of orientation and the piezoelectric properties of PMN-PT. BT template was prepared via the topochemical microcrystal conversion method, and its size was controlled by changing the BaBi4Ti4O15 precursor's size. The degree of orientation was high in tape-caste PMN-PT, and its piezoelectric properties were considerably improved. The results manifest the influence of the size of the BT template on the degree of orientation and on the piezoelectric properties of textured PMN-PT.


CJ:P11  Effectiveness of Magnetic Sheets in Suppressing Magnetic Leakage in Automobile Wireless Energy Transfer Systems
T. TAKEO, M. KAWAGUCHI, Mie University, Tsu, Mie, Japan; T. ISHIHARA, T. MATSUZAKI, Kitagawa Ind. Co., Ltd., Kasugai, Aichi, Japan

Recently, wireless energy transfer has been available for charging or powering consumer products such as mobile phones. Currently, this technique is also being introduced for hybrid vehicles or electric cars in the automobile industry. In such systems, the coupling efficiency between transmitting and receiving antennas is probably the most important issue. On the other hand, evaluation of magnetic field leakage from a system and its suppression, if necessary, are also indispensable for safety against adverse effects to the human body. It has been known that, without any measure, magnetic field strength exceeds the regulated values stated in laws governing electromagnetic emissions in various countries. In this study, application of magnetic sheets, which are widely used as EMC components, to the suppression of magnetic field leakage from an automobile charging system is investigated. Specifically, the ability of suppression at a certain distance from the system will be evaluated by means of an electromagnetic simulation when magnetic sheets having different permeability values, shapes, sizes, etc. are installed around the antennas. Through these investigations, acceptable system arrangements will be discussed in order to fulfill the regulations being established in the industry.


CJ:P12  Gd(Al,Co)O3 Additions to Counter the Impact of High Silica Contamination in CGO
J.C.C. ABRANTES, E. GOMES, J.R. FRADE, UIDM, ESTG, Polytechnic Institute of Viana do Castelo, Viana do Castelo, Portugal; Ceramics Dep., (CICECO), University of Aveiro, Aveiro, Portugal

Inexpensive materials are required to ensure competitiveness of solid oxide fuel cells as a power source system. However, the conductivity, and long term ageing of solid electrolytes is significantly affected by contaminants, which often sets targets in the order of 50 ppm for silica and other impurities. The impact on grain boundary properties is, probably, the most well established effect of contaminants, and stimulated the so-called scavenging approach, based on additives with affinity for silica, such as additions of alumina to YSZ. Yet, the mechanisms of some additives are still debatable, as found on adding alkali earth oxides to CGO, with preferential segregation of cerates, or on adding cobalt oxide or lanthanide oxides. Some of these additives also affect sintering. Thus, the present work examines effects of Gd(Al,Co)O3 perovskites on sinterability and grain boundary properties of CGO contaminated with silica. These perovskite combine different additives with demonstrated impact on ceria-based electrolytes, and their effects are analysed by taking into account differences in affinity towards the ceria-based fluorite and silica.


CJ:P13  Bit Memory in Absorption Spectrum of Piezoelectric Resonators
F. TSURUOKA, Department of Physics, Kurume University, Fukuoka, Japan

The phenomenon of bit memory or hole burning in light absorption materials have been well studied. There, comparatively large amplitude light introduced some change of light absorption characteristics and detected holes in their absorption spectrum. We have proposed the same phenomenon in acoustic resonator of piezoelectric particles.
The piezoelectric particles, whose diameters are limited around that estimated by the applied resonant oscillation frequencies or wave length and whose absorption spectrum is slightly wide spread and flat in frequency space, might match the fundamental necessity for detection of hole burning. We applied pulsed Rf electric fields with comparatively large amplitude to the particles and detected some holes near the applied frequency. We proposed the role of plastic deformation or crystal dislocations introduced by large amplitude oscillation.
The dislocation oscillations in particles affect the oscillation damping of particle that is detected as a hole in their absorption spectrum. And they brought the apparent elastic constants that were detected in the frequency difference between the applied pulses and the detected hole positions. We discussed on the holes in some kinds of piezoelectric particles.


CJ:P14  Synthesis of Multiferroic Thin Films Based on Fluoride Phases
S. BATTIATO, G. MALANDRINO, Dipartimento di Scienze Chimiche, Università di Catania, and INSTM UdR Catania, Catania, Italy

Multiferroics represent a unique class of materials where ferro/antiferromagnetic and ferro/antiferroelectric properties coexist simultaneously exhibiting electromagnetic coupling. Such materials are being contemplated for applications in memory, read-write electronic devices. Several perovskites materials such as BiFeO3, BiMnO3 and TbMnO3 have been reported as multiferroic materials. To the best of our knowledge, there are a few reports on fluoride based materials with the coexistence of ferroelectricity and ferromagnetism.
BaMgF4 is known to be a ferroelectric and diamagnetic material. In order to induce ferromagnetism in this material, Mn was chosen as a dopant, which has been reported to induce room temperature ferromagnetism (RTFM) in ZnO and In2O3 etc..
In this work, metal organic chemical vapor deposition (MOCVD) has been applied to deposit pure and Mn doped BaMgF4.
After standardization of the synthetic procedure for pure BaMgF4, several Mn-substituted BaMgF4 thin films have been synthesized with generic composition BaMg1-xMnxF4. The structural and compositional studies pointed out to the formation of the desired phase, while functional characterizations are under course.


CJ:P15  Effects of Thickness Variation on LiCoO2 Cathode for High Capacity All-solid-state Thin Film Battery
SEUNG-HWAN LEE, EUN-SEOK KWON, JOOSUN KIM, High Temperature Energy Materials Research Center, KIST, Seoul, Korea; JOOHO MOON, Dept. of Materials Science and Engineering, Yonsei University, Seoul Korea

All-solid-state thin-film rechargeable lithium ion batteries have received attention as a power source for micro-devices. Considerable interest has developed in the fabrication of LiCoO2 films with desirable properties as a cathode with high capacity for all-solid-state thin-film battery. The thickness and crystallographic orientation of LiCoO2 films in as-deposited state and/or post-heat-treated state can significantly affect to the electrochemical performance because the reaction pathway is limited to the geometrical interface between cathode and electrolyte film. LiCoO2 film, therefore, possessing thin and specific crystallographic direction for easy Li-ion diffusion delivers high specific capacity even at high rate of charge/discharge condition.
We have examined the electrochemical properties of LiCoO2 cathode films with different thickness in the context of exploring the optimum material usage, and tried to reveal the contribution of crystallographic orientation. The electrochemical performances of LiCoO2 films have been analyzed in terms of area and volume of active materials. Optimum thickness have been observed at each rate of charge/discharge condition. Fast discharge condition prefers thinner film as well as suppressed (003) texturing.


CJ:P17  Proton Conductivity of the 12R-Type Hexagonal Perovskites Sr3RENb3O12 (RE = La,Nd)
A.L. CHINELATTO^{1, 2}, C. TABACARU¹, G.C. MATHER¹, ¹Instituto de Cerámica y Vidrio, CSIC, Cantoblanco, Madrid, Spain; ²Department of Materials Engineering, State University of Ponta Grossa, Ponta Grossa, Brazil

The 12R-type hexagonal perovskite structure (ABO₃) is found in various stacking arrangements of hexagonal- and cubic-close-packed AO₃ layers, leading to a rich structural complexity. We have recently shown that undoped and acceptor-doped Sr₃LaNb₃O₁₂ displays proton conductivity in wet oxidizing atmospheres. In this work we study proton transport in two 12R-type hexagonal perovskite systems: Sr₃NdNb_3-xTi_xO_12-δ (0 ≤ x ≤ 0.06) and Sr₃LaNb_3-xTi_xO_12-δ (0 ≤  x  ≤ 0.1).  Compositions Sr₃RENb_3-xTi_xO_12-δ (RE = La, Nd) were prepared by solid-state reaction. The FULLPROF program was used for Rietveld refinement of the crystal structure. Electrical measurements were performed on sintered pellets in dry and wet (H₂O, D₂O) air, O₂ and 10% H₂:90% N₂ in the temperature range 600-900°C by impedance spectroscopy. Isothermal measurements were also collected as a function of the oxygen partial pressure, pO₂. Rietveld refinement of XRD data indicated that the title phases Sr₃RENb₃O₁₂ crystallise with a 12R- type hexagonal perovskite structure (space group R3¯). Conductivity measurements indicate that both the La and Nb analogues exhibit proton conductivity in wet oxidizing atmospheres as demonstrated by a conductive isotope effect.


CJ:P18  Microstructural and Electrical Properties of Gadolinium Doped Barium Zirconate Sintered by Liquid Phase
E.B. MORAES, D.Z. DE FLORIO, UFABC, Santo André, SP/Brazil

High proton conductivity perovskites can be utilized in many important applications. In this work gadolinium doped barium zirconate ([gadolinium oxide] = 0, 5, 10, 15 and 20% mol) was prepared by Pechini method from nitrates precursors. The powders were studied by simultaneous thermal analysis, X-ray diffraction, and scanning electron microscopy. These powders were then uniaxially pressed at 1 ton/cm2 in cylindrical discs (diameter = 10 mm and thicknes ~ 1 mm) and theirs geometrical densities were determined. These pellets were sintered at temperatures of 1623 K/1 h with and without amounts (from 0 to 14 mol %) of boric acid as sintering aid, follow by geometrical and Archimedes density measurements. Phase analysis was carried out by X-ray diffraction, and fracture and polished samples surfaces were observed in scanning electron microscopy. The parallel faces of each sample was painted with platinum paste and electrical characterized by impedance spectroscopy in the frequency range from 32 MHz to 1 Hz, under static air and standard mixture (3% hydrogen/97% nitrogen) flow, in the RT up to 1273 K. The main results indicate that dense (>96 % of theoretical density) barium zirconate perovskite phase was obtained for samples liquid phase sintered with 3.5 mol % of boric acid.


CJ:P19  Correlation between Powder Characteristic and Microstructure Development of Y-doped BaCeO3
H.E. ARAUJO, D.P.F. DE SOUZA, PPGCEM - DEMA/UFSCar, Sao Carlos, SP/Brazil

In the present work the microstructural development of solid electrolyte based on barium cerate was investigated. BaCe0,9Y0,1O3-d powder was prepared by citrate process with stoichiometric ratios of cerium, barium and yttrium nitrates. The calcination time at 1100°C of precursor powder ranged between 1.5 and 10h. X-ray diffraction (XRD) and X-ray fluorescence (XRF) were used to follow the crystalline phase formation and the chemical composition of the calcined powder. Pellets of calcined powder were isostatic pressed at 200 MPa and sintered at 1350°C for 10h. Scanning electronic microscopy (SEM) was used to microstructure analysis of sintered samples. The increase of calcination time promoted significant change in the XRD pattern and also in the chemical composition. Same behavior was observed comparing the XRD and chemical composition of the powder and respective sintered sample. Accurate SEM analysis of the microstructure, using higher magnification, shows that the microstructure development is strongly dependent of the chemical composition and the crystalline phase present on the powder after calcinations. The degree of heterogeneity of the microstructure increased with deviation from stoichiometric composition.