bluuebunny/crossref_metadata_2025 huggingface dataset:
High Resolution Scanning Electron Microscope Examination of the Fish Scale: Inspiration for Novel Biomaterials
Authors: Ravneet Ravneet , Sharma M.L. , Kang H.P.S.
Published: December 2009

A Scanning Electron Microscopic study on the fish scale of Cyprinus carpio communis (freshwater carp), depicts remarkable structural and compositional characteristics which may be used as inspiration for novel biomaterial design. The fracture surface structure and sintered fish scale reveals an osseous layer on its dorsal side. It has a compact heterogeneous crystalloid-like structure of assorted shapes and sizes. The ventral side is made of orthogonally arranged mineralized needle like crystalloids template embedded in a fibrillary plate. Frozen scales revealed that this dorsal layer may contain high atomic number elements as it appeared bright with back scattered electron signals. The ventral side consists of collagen plates and a matrix, which are arranged orthogonally in a double-twisted, plywood-like structure. There are alternate crystalloid and matrix which are arranged orthogonally and forming 15-17 layers in between these two sides. This provides useful information of scale composition. Design features from the structure of the fish scale may be useful in the development of functional biomaterials, in various different fields including nano-composites, biopolymers and natural source of hydroxyapatite, used in applied therapeutic, pharmaceutical industries and semiconductor technology. The tolerance of the fish scale to high temperature and very low temperature cooling revealed unique characteristics for biomaterial fabrication. The orthogonally arranged ventral side plates of collagen embedded in proteoglycans may also prove to be a good source of scaffold material for cell culturing for tissue engineering.
Characterisation of Foamed Porous Alumina Tissue Scaffolds
Authors: Soh E. , Ruys Andrew John
Published: December 2009

A porous tissue scaffold depends on its ability to provide functional balance between mechanical strength, pore properties and interconnectivity of pores. High porosity levels, typically greater than 90% and pore sizes above 100µm are required for tissue growth and fixation. Alumina is a stable and very strong bioceramic which, when doped with calcium and phosphate ions, can potentially combine bioactivity with high porosity and high strength. Highly porous alumina foams were synthesized through heat induced chemical breakdown of precursor salt solutions. Pore sizes achieved for foamed alumina with moderate mole fractions are generally larger than 100µm. Foamed alumina with mole fractions on the extreme high and low ends shows lower average pore sizes. Compressive strength of synthesized foams falls in the range of 100kPa to 230kPa, significantly higher than porous biodegradable polymer tissue scaffolds. The significance of this work is that scaffolds can be produced with the unique combination of high porosity, high strength and biocompatibility.
Geometrical & Interfacial Modulation of a Biomimetic Spinal Implant
Authors: Lok P. , Boughton Philip , Kishen T. , Diwan Ashish D.
Published: December 2009

The nucleus of a spinal disc is seamlessly connective and protectively supportive of the joint within which it is enveloped. A range of nucleus prosthesis configurations have been proposed and applied with some success. Those that have demonstrated clinical efficacy have approximated physiological form and function using established biomaterials while preserving key anatomical structures. The minimally invasive biostable, biomimetic Columna Disc Device (CDD) partial spinal disc replacement has been developed to clinical trial stage. It mimics the geometry and response of the nucleus that it replaces. While the implant configuration and materials have been set, the geometry and interfacial properties of this prosthesis may be modulated to account for versatility in surgical deployment, implant stiffness, and subsequent long-term tissue remodelling response. FEA models were developed to study effects of implant jacket geometry and surface properties on implant deployment and biomechanics. Studded and dimpled textures provide a method for increasing surface area to diffuse jacket-filler interfacial stress and similar for the implant-tissue junction. Surface texture design elements observed in nature can protect against delamination and interlayer slippage. This is the case with adherent outer layers of human skin. A textured implant design is also proposed to guard against third body wear by housing debris remote of wear sites and by reducing sliding. The periodically varying strain fields provided by the textured jacket may also help mitigate for tears by diverting and arresting micro-fissures. Increasing friction at the implant-tissue interface to the point of tissue-attachment was shown to increase the stiffness of the implant in axial-loading. In contrast, increasing bulk surface area is expected to contribute to a decrease in implant stiffness. This is, however, dependent on the intimacy and properties of interfacing tissues.
Methods for Achieving Soft Tissue Scaffold Sterility
Authors: Baume Alex , Coleman Nick , Boughton Philip
Published: December 2009

The manufacturing process for in vitro tissue culture products and medical devices relies on a validated sterilization route for ensuring product sterility, safety and performance. Two key aspects that contribute toward final sterilization validation are (1) the reliable estimation of product bioburden and (2) the development of a proficient sterile packaging system. Bioabsorbable composite systems and architecture of tissue scaffolds can lead to numerous challenges for bioburden testing and packaging design. This study is concerned with the development of bioburden assessment methods and packaging systems for Variotis™; a soft tissue engineering scaffold. A bioburden test method relying on mechanical agitation was established. Bioburden assessment was achieved by recovering Geobacillus stearothermophilus spore inoculant for analysis. A packaging system was developed which provides adequate protection for Variotis™ scaffolds while meeting other user/sterilization requirements for research grade product. The guidelines and design approaches included in this study are generally applicable to other tissue engineering scaffold and medical devices.
Effect of PAA-NH4 Dispersant on Dispersibility of Aqueous Pb(Zr, Ti)O3 Slurries and Piezoelectric Properties of Resultant Sintered Bodies
Authors: Fujioka Masato , Yamaguchi Toshiaki , Sakamoto Wataru , Kikuta Koichi , Hirano Shin Ichi
Published: December 2009

The effect of poly ammonium acrylate (PAA-NH4) dispersant on the dispersibility of Pb(Zr,Ti)O3 (PZT) slurries and the piezoelectric properties of resultant PZT sintered bodies was investigated for the establishment of environmentally friendly aqueous processing. The dispersion state and viscosity of PAA-NH4-added PZT aqueous slurries strongly depended on the slurry pH. Well-dispersed PZT slurries with negligibly small Pb2+ dissolution were obtained in the alkaline side due to the electrostatic steric hindrance effect of adsorbed polyelectrolyte dispersant molecules with a high dissociation ratio of carboxylic acid groups. The homogeneous dense microstructure and the enhancement of the piezoelectric properties of PZT ceramic bodies were achieved by preparing the aqueous PZT slurry with an optimum amount of dispersant.
Characteristics of Synthesized Diamond Films by Using CACVD Techniques at High Temperatures
Authors: Wongprasert Y. , Pongsai S.B.
Published: December 2009

This paper presents synthesized diamond films by using combustion activated chemical vapor deposition (CACVD) techniques. The characteristics of diamond films have been studied at wide ranges of temperature (30-400°C). The resistance of diamond films has been determined for hydrogen termination times of 5, 10, 15, and 20 minutes, and at the operation temperatures of 500, 600, and 700°C. The investigation found that, at 30°C a synthesized diamond film has a high resistance (1010 ), whereas at high temperatures (100-400°C) the resistance has decreased from 4.04 M to 2.42 M. The result obtained from the hydrogen termination showed that the resistance has decreased by 105-106  (at 30°C). Summarily, it can be stated that the higher the hydrogen termination times and operation temperatures, the lower the resistance of diamond films.
Fabrication of Dielectric/Conductive Hybrid Artificial Superlattices Using Molecular Beam Epitaxy Method
Authors: Yonezawa Yu , Kinbara Hiroyuki , Umehara Hiroki , Kakemoto Hirofumi , Hoshina Takuya , Takeda Hiroaki , Tsurumi Takaaki
Published: December 2009

Artificial super-lattices of [(BaTiO3)/(SrTiO3)10]4 (BTO10/STO10) were fabricated on STO(001) substrate by the molecular beam epitaxy method (MBE), and the molecular layers of SrRuO3(SRO) was introduced into these superlattices as conductive layers. The superlattices introduced two conductive layers showed the enormous dielectric permittivity. On the other hand, the permittivity of the superlattice introduced one conductive layer was almost same as that of BTO10/STO10. In the case of introducing two conductive layers, the moving electrons between two layers induced the interfacial polarization. Especially, the superlattice with two SRO conductive layers, the distance between these layers in a superlattice is 18 molecular layers, showed the highest relaxation frequency 132 kHz and biggest capacitance.
Realization of Tunable Varactors Using Bi1.5Zn1.0Nb1.5O7 Thin Films
Authors: Sudheendran K. , Raju K.C. James
Published: December 2009

Cubic pyrochlore bismuth zinc niobate thin films are known to exhibit voltage dependent dielectric properties. In this paper, we are demonstrating the fabrication and characterization of interdigital (IDC) and circular patch (CPC) capacitors using the pulsed laser deposited Bi1.5Zn1.0Nb1.5O7 (BZN) thin films on sapphire and platinised silicon substrates respectively. The IDCs fabricated are having 12 fingers of width 12 m each and separated by a gap of 8 m. The CPC are having circular patches with inner radius of 100 m and concentric ground plane with a radius of 300m. The electrical properties of these capacitors were characterized both at low frequencies and at microwave frequencies. The CPC varactors were having a tunability of 25% at 15 Volts.
The calculated capacitance of the IDC varactor at 5.3 GHz with 0 V dc bias was 1.1 pF, which has got changed to 0.99 pF by the application of 30 Volts exhibiting a tunability of 10%.
Influence of an External Magnetic Field on Injected Charges of a Cr2O3/Fe/CeO2/Si MIS Capacitor
Authors: Yokota Takeshi , Murata Shotaro , Kito Shinya , Gomi Manabu
Published: December 2009

We investigated the influence of an external magnetic field for the carrier injection process of a metal (Au) / insulator (Cr2O3/Fe/CeO2) / semiconductor (Si) (MIS) capacitor, in which the insulator consists of magnetic materials. By applying an electric field, electrons propagating through the CeO2 layer from Si were injected into the Fe or an oxygen deficiency layer formed around the Fe layer. When a magnetic field was applied, the hysteresis window width of this capacitor was reduced. I-V curve analyses under a magnetic field revealed that this reduction was more likely due to the magnetic state of the Fe layer and the interaction between Fe and Cr2O3.
Crystal Growth and Electrical Properties of Na0.5Bi0.5TiO3-BaTiO3 Lead-Free Ferroelectric Piezocrystals
Authors: Chen Chao , Zhao Xiang Yong , Liu Hong , Ge Wen Wei , Luo Hao Su , Jiang Xiang Ping
Published: December 2009

(1-x)(Na0.5Bi0.5)TiO3-xBaTiO3 (abbreviated as NBBT100(1-x)/100x or NBBT100x) solid solution single crystals with x=0, 0.06, 0.08, 0.10, 0.20, 1.0 were grown using top-seeded solution growth (TSSG) method. Dielectric, piezoelectric and ferroelectric properties of NBBT crystals were investigated as a function of temperature, frequency, composition and crystal orientation. The temperature (Tm) corresponding to dielectric maximum and the depolarization temperature (Td) decrease with increasing x. The <001> oriented NBBT90/10 single crystal shows excellent piezoelectric performance with piezoelectric constant (d33) value about 275pC/N and exhibits relatively smaller coercive field (Ec) of 2.49 kV/mm and dielectric loss tanδ of 2.9 %, indicating a more adaptive engineered domain structure.
Li(Ga1-xMx)O2 (M: B or Al) Single Crystals Grown by Floating Zone Method
Authors: Kimura Hideo , Tanahashi Rumi , Maiwa Koji
Published: December 2009

Li(Ga1-xMx)O2 (M: B or Al) single crystals are grown by Floating zone method. These crystals are characterized from the viewpoint of the substitution of M, such as lattice parameter (lattice volume) change, piezoelectric properties and nonlinear optics. The lattice volume is decreased with the increase of Al content for Al-substitution largely, but the change is a little for B-substitution.
Crystallization Behavior of Ferroelectric Glass-Ceramics of the Na2O-Nb2O5-Al2O3-SiO2 System Contained TiO2
Authors: Niyompan Anuson , Srisurat Kanita , Tipakontitikul Rungnapa
Published: December 2009

The ferroelectric glass-ceramic of the composition Na2O-Nb2O5-Al2O3-SiO2 was prepared by controlling crystallization of the glass that added with small amount of TiO2. The effect of TiO2 content on crystallization behavior and the dielectric property were determined. X-ray diffraction studied indicated that NaNbO3, NaNbO8 and a compound of alkali alumino silicate composition were readily formed in the as-quenched glass as the product of phase separation. After treatment at 700oC for various times, NaNbO3 volume fraction was found to increase with time. Crystalline size of the NaNbO3 was lower than 300 nm and it was developed with treatment time. Presence of TiO2 had considerably effect on NaNbO3 volume fraction when treatment time shorter than 1.0 h. The dielectric response of the glass-ceramic samples was found to arise from all contributions of crystalline phases and glass matrix responds.
Zinc Self-Diffusion in Isotopic Heterostructured Zinc Oxide Thin Films
Authors: Matsumoto Kenji , Adachi Yutaka , Ohgaki Takeshi , Sakaguchi Isao , Nakagawa Tsubasa , Ohashi Naoki , Haneda Hajime
Published: December 2009

Zinc isotopic heterostructured zinc oxide thin films of 64ZnO/68ZnO/64ZnO were synthesized using pulsed laser deposition. The pulsed laser was first irradiated onto a polycrystalline target of 64ZnO to deposit the 64ZnO layer, then onto the 68ZnO target to prepare the 68ZnO layer and finally, the 64ZnO target was used again. The 64ZnO/68ZnO/64ZnO layered thin film was thus obtained. The thin films were annealed at various diffusion annealing temperatures. Diffusion profiles of the zinc isotopes due to the annealing were evaluated using secondary ion mass spectrometry (SIMS). The diffusion coefficients were slightly higher near the interface between the thin film and the substrate (the inner region) compared to the near surface (the outer region).
Observation of Diffusion Behavior in Al-Implanted ZnO Single Crystal
Authors: Nakagawa Tsubasa , Sakaguchi Isao , Matsumoto Kenji , Uematsu Masashi , Haneda Hajime , Ohashi Naoki
Published: December 2009

Diffusion behaviors of aluminum (Al) in zinc-oxide (ZnO) single crystals were measured by means of ion implantation technique and SIMS depth profiling. It was found that Al concentration profile had a peculiar shape with a constant-concentration region and a steep tail, which was also found in profiles of other donors such as Ga and In. Detailed analysis of the profiles revealed that the diffusivity of Al was proportional to the square of Al concentration and its intrinsic diffusivity was much smaller than previously reported values. Oxygen diffusion experiments were also performed and the implantation of Al ions enhanced the oxygen diffusion coefficients by about 20 times. This result indicates that oxygen interstitial diffusion occurs in n-type ZnO.
Redistributing Unintentional Defects Induced by Heavy Ion Implantation in ZnO Ceramics
Authors: Sakaguchi Isao , Nakagawa Tsubasa , Matsumoto Kenji , Hishita Syunichi , Adachi Yutaka , Ohashi Naoki , Haneda Hajime
Published: December 2009

The relationship between the defect structure and luminescence property of ZnO ceramics implanted with Ar of 2×1015 – 60×1015 ions/cm2 was studied. After annealing, the heavy dose-implanted sample (Ar ≥ 30×1015 ions/cm2) was characterized by a luminescence peak at the 730-nm wavelength. Defects in the implanted region formed voids during post-annealing. Oxygen tracer experiments indicated that grain boundary diffusion in the implanted region was enhanced significantly.
Crystallization and Raman Spectra of Langasite-Type Na2CaGe6O14, Na2SrGe6O14 and Pb3Ga2Ge4O14 in Corresponding Glasses
Authors: Takahashi Yoshihiro , Fujiwara Takumi , Benino Yasuhiko , Komatsu Takayuki
Published: December 2009

We investigated the crystallization behavior of langasite-type phases in the stoichiometric corresponding glasses, i.e., Na2CaGe6O14, Na2SrGe6O14 and Pb3Ga2Ge4O14. The langasite-type phases singly were formed by heat-treatment in the glasses. Raman spectroscopy revealed the structural similarity on the scale of short-/medium-range order between the langasite-type phases and the corresponding glasses. Furthermore, we also examined the temperature dependence of second-harmonic (SH) intensity of the langasite-type phases. The SH-temperature curves exhibited an anomalous behavior, implying a structural change, e.g., isomorphous phase transition.
Sintering of Ba1-XSrXTiO3 Powders Prepared Using KOH-KNO3 Molten Salt Method
Authors: Kishiki Tomohiko , Higuchi Masashi , Asaka Takashi , Azuma Yasuo , Katayama Keiichi
Published: December 2009

Barium strontium titanate (BST), which has a typical perovskite-type structure, shows excellent electrical properties. BST powders were synthesized by heating mixtures of commercial reagents with an excess of TiO2 in molten salts of KOH and KNO3, and the sintering behavior of the resulting powders was evaluated. The sample with the highest density of 95% was obtained by sintering of the BST powders.
Pinched Hysteresis Scaling in Hybrid-Doped BaTiO3
Authors: Sucharitakul Sukrit , Prasertpalichat Sasiporn , Yimnirun Rattikorn , Laosiritaworn Yongyut
Published: December 2009

In order to investigate the mechanism of hybrid doped ferroelectric, BaTiO3 sample was prepared via conventional mixed-oxide method. The sample was then subjected to doping process with Fe3+ as acceptor dopant and Nb5+ as donor dopant. With varied concentration of acceptor dopant from 0.5 to 1 %M at fixed 1%M of donor, hysteresis property was obtained via Sawyer-Tower circuit. The hysteresis property of the sample was observed to vary over time by influence of ageing effect. By numerical scaling, the stretched exponential decay behavior of the system was obtained to gain the better insight of ageing mechanism of hybrid doped ferroelectric. With stretched exponential fitting, stretching parameter of lower doped Nb5+ were observed lower than that of equivalently doped Nb5+.
Synthesis of Nano-Sized Barium Titanate Powder by Rotary-Hydrothermal Process
Authors: Kubo Takashi , Hogiri Masayuki , Kagata Hiroshi , Nakahira Atsushi
Published: December 2009

Nano-sized BaTiO3 powders with narrow size distribution and the high tetragonality were attempted to synthesize by the rotary-hydrothermal process in water system, using two kinds of commercial anatase-type TiO2 (ST21/ST01) with different particle size and Ba(OH)2. The rotary-hydrothermal syntheses were done with the rotary-speed of 20 revolutions per minute at 523 K for 24 h. Highly- and mono-dispersed BaTiO3 powders were successfully synthesized by applying the rotary-hydrothermal process. For rotary-hydrothermal synthesis, it was found that the average size, tetragonality, and quality of the BaTiO3 particle strongly depended on the particle size of the starting material. In the case of using ST01 as a starting material, BaTiO3 nano-powders mainly composed of coarse-faceted particles (average particle size = ca.100 nm) with the tetragonal phase and very little lattice defects were successfully synthesized.
Sintering Behavior of Silver Particles in Electrode for Multilayer Ceramic Substrate
Authors: Okada Atsuyuki , Ogihara Takashi
Published: December 2009

Several types of Ag powder were used as electrode paste for a multilayer ceramic substrate. The shrinkage behavior of the silver powders was investigated during the sintering. Bending and cracking were frequently observed on the substrate when coarse powders that show a broad size distribution and aggregation were used. The shrinkage curve of the Ag paste obtained by spray pyrolysis agreed well with that of the substrate. Furthermore, the electrical properties of the Ag paste were also determined. The resistivity of a silver electrode sintered at 900°C was about 2.00×10-6 Ω･cm.
The Influence of BaTiO3 Tetragonality by Solid State Synthesis on MLCC’s Dielectric Characteristics
Authors: Hogiri Masayuki , Kagata Hiroshi
Published: December 2009

BaTiO3 powders with particle size 0.1μm were made by solid state synthesis. To make high tetragonality BaTiO3 powder, mixture of TiO2 and BaCO3 was calcined in vacuum condition. And to make low tetragonality BaTiO3 powder, the mixture was calcined in air condition. With each powder, MLCCs with Ni-internal electrode were fabricated. Relationships between temperature and relative dielectric constant of MLCCs’ dielectric layers were analyzed and their dielectric grains were observed by TEM-EDS. As the result, MLCC made from high tetragonality BaTiO3 powder had good temperature characteristics and core-shell dielectric grains.
Sensing High Concentrations in Air of H2 Based on Spin-Coated Films of Flame-Spray-Made SnO2 and Pd/SnO2 Nanoparticles
Authors: Liewhiran Chaikarn , Wisitsoraat Anurat , Phanichphant Sukon
Published: December 2009

Flame Spray Pyrolysis (FSP) was performed for the synthesis of high specific surface area (SSABET) of SnO2 nanopowders (141.6 m2/g) and supported palladium (Pd) nanoparticles containing 0.2-3 wt%Pd with controlled size and a crystallinity in a single step. The particles properties were further characterized by XRD, BET and TEM analyses. The crystalline particles were used for sensing film preparation by spin coating. It was found that the flame-spray-made 0.2 wt%Pd/SnO2 sensor showed higher and faster response to reducing H2 gas than pure flame-spray-made SnO2 sensor.
Improving the Performance of High Temperature Protonic Conductor (HTPC) Electrolytes for Solid Oxide Fuel Cell (SOFC) Applications
Authors: Fabbri Emiliana , Pergolesi Daniele , D'Epifanio Alessandra , di Bartolomeo Elisabetta , Balestrino G. , Licoccia S. , Traversa Enrico
Published: December 2009

This work investigated the possibility of coupling the high conductivity of cerates and the good chemical stability of zirconates as proton conductor electrolytes for solid oxide fuel cells (SOFCs). Two different approaches are discussed: the synthesis of barium cerate and zirconate solid solutions, and the fabrication of a bilayer electrolyte made of a Y-doped barium cerate pellet covered by a thin protecting layer of Y-doped barium zirconate. The chemical stability of the tailored samples was tested exposing them to 100% CO2 atmosphere at 700°C for 3 h. X-ray diffraction (XRD) analysis was used to investigate the phase composition of the specimens before and after the CO2 treatment. Electrochemical impedance spectroscopy (EIS) measurements were carried out in humidified H2. Hydrogen-air breathing fuel cell experiments were carried out at 700°C.
Fabrication and Characterization of Organic Semiconductor Based Gas Sensor
Authors: Atique Munirah , Shabbir Ghulam , Mehmood Mazhar
Published: December 2009

Thin films of organic semiconductor based azo-dye, OD 25, of the average thickness, 750 ± 10 nm, were desposited successfully on the glass substrate for gas sensing applications. Electrical conductivity was of the film as measured by impedance spectroscopy, showed an increase with frequency that was attributed to non-metallic nature of the film. Moreover, single conduction mechanism and negligible contact resistance showed good quality of the sensor film. Deposited film with Al and Ag electrodes showed good conductance when exposed to water and ethanol vapors.
Piezoelectric Ceramics for High Temperature Applications
Authors: Higuchi Yukio , Ogawa Hirozumi , Kuroda Daisuke , Kimura Masahiko , Takagi Hiroshi , Sakabe Yukio
Published: December 2009

Ceramic materials based on lead titanate, lead niobate and bismuth layer-structured ferroelectrics (BLSF) were studied to develop piezoelectric ceramics for high temperature sensor applications. Compositional modification enabled lead titanate and lead niobate type ceramics to exhibit good piezoelectric properties at 500°C . The Curie temperature for one BLSF, CaBi4Ti4O15 was close to 800°C, though the piezoelectric constant was smaller than those of lead titanate and lead niobate ceramics. These ceramics seem to be good candidates for use as high temperature sensor materials.
In addition, textured SrBi2Nb2O9 (SBN), another BLSF, ceramics with various orientation factors were fabricated through the templated grain growth (TGG) method. The resonant frequency of 76% textured SBN varied linearly with temperature and exhibited stable temperature characteristics. The temperature coefficient of the resonant frequency was –0.85 ppm/°C from –50 to 250°C, and was smaller than that of a quartz oscillator. Therefore, textured SBN ceramics are suitable for use as a resonator material when stable resonant frequency is needed in a high temperature range.
Crystal Structure Analysis of Barium Titanate – Bismuth Perovskite-Type Oxide System Ceramics and their Piezoelectric Property
Authors: Yamato Keisuke , Kumada Nobuhiro , Moriyoshi Chikako , Kuroiwa Yoshihiro , Lee Bong Yeon , Iijima Takashi , Wada Satoshi
Published: December 2009

Barium titanate (BaTiO3, BT) – bismuth lanthanum zinc titanium oxide [(BiyLa1-y)(Zn0.5Ti0.5)O3, ByL1-yZT] solid solution ceramics were prepared to enhance Curie temperature (TC) of BT, 132 °C, to 200 °C. As the raw materials, nanoparticles were used to make sintering temperatures lower. Optimization of calcination and sintering conditions resulted in a formation of a perovskite single-phase, and their densities were always greater than 94 %. The synchrotron XRD measurement revealed that the crystal structures were assigned to rhombohedral 3m. Temperature dependence of dielectric property revealed that for the 0.5BT-0.5BZT ceramics, TC was 230 °C. Moreover, La-doping into BT-BZT ceramics resulted in decrease of TC significantly. Finally, their piezoelectric properties were measured by electric-field dependence of strain at room temperature, and for the 0.6BT-0.4BZT ceramics, the apparent d33 was measured at 250 pC/N.
Dielectric and Ferroelectric Properties of (Cr,Nb)-Doped Lead Zirconate Titanate Ceramics
Authors: Ketsuwan Piyachon , Prasatkhetragarn Anurak , Ananta Supon , Huang Chien Chih , Cann David P. , Yimnirun Rattikorn
Published: December 2009

The 3 mol% Nb2O5 doped Pb(Zr0.52Ti0.48)O3 with addition of 1-3 mol% Cr2O3 prepared via the solid-state reaction technique have been investigated. The XRD shows that a sample is primarily in both tetragonal and rhombohedral phases coexist and the amount of rhombohedral phase decreases that is due to the donor (Nb) dopant reduces the number of oxygen vacancies and leads to a lower amount of rhombohedral phase. The maximum dielectric constant tend to decrease with increasing Cr doping concentration from 0.1 to 1 mol%. Further increase in Cr concentration, the maximum dielectric constant increase dramatically. The hysteresis loop measurements, the electrical coercivity and the remnant polarization do not show a systematic trend at low concentration of Cr doping. It is possibly due to the partial solubility of Cr doping. The observations clearly indicate the hardening behavior at higher concentration because of more solubility of Cr.
XPS Characterization of Perovskite Relaxor PNN Ceramics Prepared by Corundum Precursor Method
Authors: Srisombat Laongnuan , Khamman Orawan , Yimnirun Rattikorn , Ananta Supon , Lee T.Randall
Published: December 2009

Perovskite ferroelectric PNN ceramics have been obtained from oxides by sintering in air, using a two-stage process with corundum Ni4Nb2O9 precursor. Under suitable firing condition, XRD analysis revealed that the ceramics consist of 100% perovskite phase. The SEM, EDX, and XPS techniques were employed to investigate the chemical composition of the surfaces of the PNN ceramics. Fluctuation in chemical composition, precipitation of NiO and the Pb-Ni-Nb-O phase different from perovskite were found.
Mechanical and Electrical Properties of Pb(Zr,Ti)O3 Ceramics Prepared by Aerosol Deposition
Authors: Miyoshi Tetsu
Published: December 2009

Full-dense bulk Pb(Zr,Ti)O3 (PZT) ceramics with various grain sizes were prepared by aerosol deposition (AD) employing various firing temperature from 800 to 1200°C. It was confirmed that the Hall-Petch relationship is obeyed in AD-processed PZT ceramics over the almost whole grain size range, which is indicating that only grain size could be the determining factor of hardness in AD since density is almost constant against the grain size. As compared with conventional sintering technique, AD-processed PZT ceramics exhibited higher hardness and higher or at least equivalent electrical properties over the whole grain size range investigated, which is indicating that the piezoelectric ceramics with improved mechanical properties can be realized by AD without any sacrifice in electrical properties.
Artificial Neural Network Modeling of Ferroelectric Hysteresis: An Application to Soft Lead Zirconate Titanate Ceramics
Authors: Laosiritaworn Wimalin S. , Yimnirun Rattikorn , Laosiritaworn Yongyut
Published: December 2009

In this work, the Artificial Neural Network (ANN) was used to model ferroelectric hysteresis using data measured from soft lead zirconate titanate [Pb (Zr1−xTix)O3 or PZT] ceramics as an application. Data from experiments were split into training, testing and validation dataset. Four ANN models were developed separately to predict output of the hysteresis area, remnant, coercivity and squareness. Each model has two neurons in the input layer, which represent field amplitude and field frequency. The ANNs were trained with varying number of hidden layer and number of neurons in each layer to find the best network architecture with highest accuracy. After the networks have been trained, they were used to predict hysteresis properties of the unseen testing patterns of input. The predicted and the testing data were found to match very well which suggests the ANN success in modeling ferroelectric hysteresis properties obtained from experiments.
Mixed Conduction of Proton and Electron in Tungsten Phosphate Glass and its Hydrogen Transport
Authors: Fujitsu Satoru , Kawazoe Hiroshi
Published: December 2009

The transference number of protons and the hydrogen transport behavior through tungsten phosphate glass have been measured through the use of a concentration cell. Based on measurement of the electrical motive force by changing the hydrogen partial pressure of both sides of a specimen glass kept in the concentration cell, the ionic transference number was estimated to be 48%. When one side is kept in hydrogen and the other in nitrogen, hydrogen transport is observed and its quantity is accelerated by applying a positive dc bias on the hydrogen side. After applying the dc bias continuously for over 1 h, the hydrogen transport is abruptly increased with no cracks and the hydrogen flux is 1.510-3 molcm-2s-1.
Effect of Sendust Particle Size on Absorption Characteristics of Composite Electromagnetic Wave Absorber
Authors: Sakai Kenji , Wada Yoichi , Sato Yuuki , Yoshikado Shinzo
Published: December 2009

The effects of the particle size of sendust, which is an alloy of Al 5%, Si 10%, and Fe 85%, on the absorption characteristics of composite electromagnetic wave absorbers made of polystyrene resin and sendust were investigated in the frequency range from 1 to 40 GHz. The size of sendust particles was varied between approximately 5 and 20 m. A metal-backed single-layer absorber made of 20 m sendust particles absorbed more than 99% of electromagnetic wave power at frequencies above 20 GHz. Meanwhile, a composite made of 5 m particles exhibited a return loss of less than −20 dB in the frequency range of not only several GHz but also above 30 GHz. In addition, the relative complex permeability r* was shown to be controlled by adjusting the particle size of sendust, and an electromagnetic wave absorber with a flexible design was proposed.
Electrical Properties and Piezoelectric Properties of CaBi2Ta2O9-Based Ceramics
Authors: Tokusu Toji , Miyabayashi Hirokazu , Hiruma Yuji , Nagata Hajime , Takenaka Tadashi
Published: December 2009

Electrical and piezoelectric properties of CaBi2Ta2O9-based ceramics have been studied. Temperature dependence of dielectric properties indicated that the Curie temperature, TC, was 923°C. Coercive field, EC, and remanent polarization, Pr, became saturated with increasing temperature. It is expected that higher-temperature than 250°C could promote the domain wall motion during the poling treatment. From resonance and antiresonance measurements, piezoelectric properties such as the maximum phase, max, electromechanical coupling factor, k33, and piezoelectric g constant, g33, were 86.1º, 0.085 and 8.4 × 10-3 V∙m/N, at room temperature, respectively.
Electrical Properties of Pt/Nb-Doped SrTiO3 Schottky Junctions
Authors: Li Jian Yong , Ohgaki Takeshi , Matsuoka Ryota , Okushi Hideyo , Ohashi Naoki
Published: December 2009

In this study, we successfully fabricated the Schottky junctions consisting of Pt electrode and high concentration Nb-doped (0.5 wt%) SrTiO3 (001) single crystal by sputtering process. The carrier concentrations of Nb-0.5wt%-doped SrTiO3 were determined as 1020 /cm3 order by Hall effect measurement. The electrical properties of junctions were investigated by measuring their current-voltage (I-V), capacitance-voltage (C-V) characteristics at temperature range from 80K to 400K. The hysteresis feature was observed that indicating the alteration of barrier height in junctions especially at lower temperature. The donor concentration and built-in potentials calculated from C-2-V data showed large discrepancy from Hall effect measurement indicating that the junctions deviate from the ideal Schottky diode model.
Oxygen Reduction Reaction Activity of Pyrochlore Oxide Electrocatalysts Prepared by Precipitation Method
Authors: Kawai Hideki , Yoshihara Kenji , Konishi Takayuki , Saito Morihiro , Kuwano Jun , Shiroishi Hidenobu
Published: December 2009

The Mn-doped pyrochlores Pb2Ru1.5Mn0.5O7- (PRMns) samples were synthesized by a precipitation method, followed by heat-treatments at temperatures of 300-800oC. Effects of the heat-treatments on their electrocatalytic activities for oxygen reduction reaction (ORR) were examined by semi-steady state voltammetry with a rotating ring-disk electrode in 0.1 M KOH solution at 70oC. The PRMns showed the best ORR activity for the 500oC-heat-treated PRMn. The onset potential of the ORR current was over 1.0 V vs RHE, and the efficiency of 4-electron reduction was almost 100%. The maximum in the ORR activity for the 500°C-heat-treated PRMn resulted from a trade-off effect between their crystallinity and specific surface areas.
Preparation of CaBi4Ti4O15 Based Thick Films on Si Substrates by Screen Printing
Authors: Kakuda Tatsunori , Futakuchi Tomoaki , Obata Tsutomu , Sakai Yuichi , Adachi Masatoshi
Published: December 2009

CaBi4Ti4O15 based thick films were prepared by screen-printing method on Si substrates. Screen-printable pastes were prepared by kneading the CaBi4Ti4O15 powder in a three-roll mill with an organic vehicle. The remanent polarization of 6.3 C/cm2 and coercive field of 130kV/cm were obtained for the CaBi4Ti4O15 with Nb2O5 1wt% thick film fired at 1130°C. The cavity structure was prepared by etching of Si substrate. The displacement-electric field butterfly curves were obtained.
Particle Structure Analysis of Highly-Dispersed Barium Titanate Nanoparticles Obtained from Barium Titanyl Oxalate Nanoparticles and their Dielectric Properties
Authors: Kondo Shuhei , Moriyoshi Chikako , Kuroiwa Yoshihiro , Wada Satoshi
Published: December 2009

Barium titanate (BaTiO3) nanoparticles were prepared by two-step thermal decomposition method of barium titanyl oxalate nanoparticles with a size of 30 nm. The BaTiO3 particle sizes were changed from 12.3 to 142 nm by control of temperature at 2nd step. The X-ray diffraction (XRD) measurement revealed that a clear splitting of 002 and 200 planes was observed over 40 nm, and the c/a ratio of 1.0089 was obtained for the BaTiO3 nanoparticles with a size of 62.3 nm. This high c/a ratio in the BaTiO3 nanoparticles suggested that its mesoscopic particle structure was composed of very thin surface cubic layer below 5 nm. Thus, synchrotron XRD data were analyzed using a “two layers” model and a “three layers” model. The Rietveld analysis using the three layers model resulted in the particle structure with a cubic layer thickness of 2.5 nm and structure gradient layer thickness of 7.5 nm. Finally, the dielectric constant of these BaTiO3 nanoparticles with thin surface cubic layer was measured at room temperature, and the maximum dielectric constant over 30,000 was obtained at the nanoparticles with a size of 83.6 nm.
Preparation of Barium Titanate Nanoparticle Thin Films by the Electrophoretic Deposition Method Using Polyacrylic Acid as a Charge-Compensating Agent
Authors: Arimura Masashi , Makino Teruhisa , Fujiyoshi Kunitaka , Kuwabara Makoto
Published: December 2009

Using the electrophoretic deposition (EPD) method, we prepared barium titanate nanoparticle (BT-NP) thin films by depositing BT-NP monodispersed in ethylene glycol monomethyl ether (EGMME) onto an electrically conductive substrate coated with polyacrylic acid (PAA). Deposition efficiency was increased compared to conventional EPD, and the uniformity of the film thickness was also improved as a result of the BT-NPs cohesion effect of the PAA coating on the substrate in addition to the electrophoretic deposition effect of the electric field. When low-molecular-weight PAA was used, the film was reinforced since PAA, which coats the substrate, diffused close to the surface of the BT-NP film during film formation. A crack-free BT-NP film was produced with a film thickness of several micrometers.
Relaxation Phenomena of MgCuZn Ferrites
Authors: Murase Taku , Umeda Hidenobu
Published: December 2009

The decrease of initial relative permeability at 103-106Hz is observed in MgCuZn or MnMgCuZn ferrites. By measuring the temperature dependence of loss factor, the gradual deterioration of initial relative permeability is attributed to a relaxation phenomenon. The relaxation phenomena of MnMgCuZn ferrites occur in the condition of the stoichiometoric composition and the higher sintering temperatures. The activation energies of the relaxation phenomena are calculated to be 0.3-1.0eV. The relaxation times at infinite temperature are calculated to be 10-12-10-16 second. The initial relative permeability of MgCuZn or MnMgCuZn ferrites with the relaxation phenomena is higher than the value calculated from the resonance frequency and Snoek’s limit law.
Effects of Compressive Stress on Dielectric Properties of Lead-Free (Bi1/2Na1/2)TiO3-(K1/2Na1/2)NbO3 Ceramic Systems
Authors: Sareein Thanapong , Unruan Muangjai , Ngamjarurojana Athipong , Ananta Supon , Yimnirun Rattikorn
Published: December 2009

Lead-free, bismuth sodium titanate-potassium sodium niobate piezoelectric ceramics (Bi1/2Na1/2)TiO3-(K1/2Na1/2)NbO3 have been prepared by a conventional mixed-oxide method via vibro-milling technique. The (K1/2Na1/2)NbO3 (KNN)-based compositions with a morphotropic phase boundary (MPB) have shown greater advantages over another typical lead-free piezoelectric candidate material system, (Bi1/2Na1/2)TiO3 (BNT)-based MPB materials. More importantly, when used this type of material is often subjected to self-induced or external stress. It is, therefore, of interest to investigate influence of stress on properties of the ceramics. In this study, the influences of compressive stress on the dielectric properties of BNT-KNN ceramics were investigated. The dielectric properties were determined under compressive stress applied parallel to electric field. The results indicate significant changes of both properties with the imposed compressive stress. The results were explained in terms of non-180˚ domain switching and de-aging of the dielectric properties under the influence of the applied stress.
High Frequency Characteristic of Elements Substituted Hexagonal Ferrites
Authors: Hiratsuka Nobuyuki , Kakizaki Koichi , Kamishima Kenji
Published: December 2009

The initial permeability μ' (at 0.1 GHz) of Ba3Co2R0.1Fe23.9O41 (x=0.1, R= Gd, Dy, Ho, Yb) samples is higher than that of the Co2Z ferrite without substitution. In particular, μ' of Gd3+ substituted Z-type ferrite sample (x=0.1) is the highest of all samples. The substituted sample of Ba3Co2TixZnxFe24-2xO41 with x= 0.85 has a maximumμ' of 24, which is twice as large as that of the non-substituted sample with x=0. Ba3Co2-2x LixFe24+xO41(x=0-1.0) are also prepared. The sample with x=0 showsμ'of 8 at 50MHz. The maximumμ' is 24.5 at x=0.3. An apparent magnetic anisotropy constant K*, calculated by using HA* and MS, decreases. Therefore, the decrease of the magnetic anisotropy contributes to the increase of μ'.
Effect of Vibro-Milling Time on Phase Formation and Particle Size of ZnNbO6 Nano-Powders
Authors: Ngamjarurojana Athipong , Yimnirun Rattikorn , Ananta Supon
Published: December 2009

Zinc niobate, ZnNb2O6, nanopowders was synthesized by a solid-state reaction via a rapid vibro-milling technique. The effect of milling time on the phase formation and particle size of ZnNb2O6 powder was investigated. The formation of the ZnNb2O6 phase investigated as a function of calcination conditions by DTA and XRD. The particle size distribution of the calcined powders was determined by laser diffraction technique, while morphology, crystal structure and phase composition were determined via a SEM techniques. In addition, by employing an appropriate choice of milling time, a narrow particle size distribution curve was also observed.
Origin of High Q for Microwave Complex Perovskite
Authors: Ohsato Hitoshi , Koga Eiichi , Kagomiya Isao , Kakimoto Kenichi
Published: December 2009

Origins of high Q are considered on intrinsic as high symmetry, ordering structure and high density crystal structure. It was concluded that the high symmetry brings high Q instead of ordering comparing some cases as follows: As if ordering ratio of Ba(Zn1/3Ta2/3)O3 (BZT) is high of about 80%, Q values are distributed from low to high Q. Disordered BZT ceramics with high density obtained for short sintering time by spark plasma sintering (SPS) showed high Q. Ba(Zn1/3Nb2/3)O3 (BZN) with order-disorder transition showed high Q at disorder form sintered over the transition temperature. And, the disordered BZN with high Q annealed at lower temperature changed to order structure without improvement of Q.
Effect of Incubation Time on Deposition Behavior of Ruthenium Films by MOCVD Using (2,4-Dimethylpentadienyl)(Ethylcyclopentadienyl)Ruthenium
Authors: Hirano Masaki , Kawano Kazuhisa , Funakubo Hiroshi
Published: December 2009

The deposition mechanism of metal-Ru films including incubation time was investigated for Ru films prepared by metal organic chemical vapor deposition from (2,4-Dimethylpentadienyl)(ethylcyclopentadienyl)Ruthenium (DER) - O2 system. Substrates with amorphous top-layer having various Hf/Si ratio, SiO2 (native oxide)/(001)Si (SiO2), HfSiON/SiON/(001)Si (HfSiON) and HfO2/SiON/(001)Si (HfO2), were used as substrates. The deposition temperature dependence of the deposition amount at the fixed deposition time ranging from 210 oC to 300 oC revealed that the deposition amount depended on the deposition temperature below 250 oC, while it was almost constant above this temperature. Incubation time depended on the kinds of substrate at 210 oC and the substrate surface was fully covered in a shorter time with smaller deposition amount for the substrates with shorter incubation time. In addition, the film with shorter incubation time had smaller surface roughness.
Tensile Behaviour of 6082 Aluminium Alloy Sheet under Different Conditions of Heat Treatment, Temperature and Strain Rate
Authors: Torca I. , Aginagalde A. , Esnaola J.A. , Galdos L. , Azpilgain Zigor , Garcia C.
Published: December 2009

Aluminium alloys are more and more important for the automotive industry due to their high strength to weight ratio and their elevated ductility; they are used for many different parts in automobiles as exterior panels, structural parts, brake housings and others. However, their formability at room temperature is limited. This inconvenient can be improved by increasing the forming temperature of the part. That lack of formability has lead to this research project dealing with the tensile behaviour of aluminium alloys sheets, at different conditions of temperature and strain rate. The analyzed material has been 6082 aluminium alloy, under two different heat treatment conditions (O and T6). Material testing has been carried out in a temperature range between room temperature and 250°C, and a strain rate range between 0.001s-1 and 0.1s-1. Testing samples have been obtained from laminated sheet of 1.5mm thickness. This article shows that the alloy under T6 condition has a reduced formability, even in warm conditions. In order to get higher deformation values an annealed condition is proposed to form the material. The effect of T6 heat treatment and O annealing treatment in the uniaxial warm formability is discussed and a microstructural analysis is also presented in order to understand the differences on the alloy behaviour.
Creep Behaviour of Closed Cell Aluminium Foams from Stress Relaxation Tests
Authors: Carcel B. , Carcel A.C. , Arrué P.
Published: December 2009

Creep behaviour of closed cell aluminium foams and transitions from power law to power law breakdown (PLB) creep regimes are investigated from results of stress relaxation tests (SRT) carried out on Alporas foams with densities between 0.20 to 0.32 g/cm3. Tests were carried out at temperatures between 200°C and 300°C and stress relaxation was measured from the collapse stress under compression of the foams. Under similar foam density, temperature and stress conditions, the values of strain rate calculated from SRT tests were of the same order of magnitude than those previously reported in the literature from conventional constant load creep tests. Under stress values close to the collapse stress, the creep mechanism seems to follow a PLB regime, with values of the power law exponent n=10-17, much higher than those corresponding to the power law creep in the solid material (n=4.4-6.5) and with activation energy values close to Q = 150 KJ/mol. Having in mind the limitations of available creep models for closed cell foams and the need for additional experimental results, the use of SRT testing would offer advantages for the assessment of the high temperature behaviour of aluminium foams, due to its lower testing times and reduced experimental effort.
Superplasticity in Ceramics: Applications and New Trends
Authors: Domínguez-Rodríguez Arturo , Gómez-García D.
Published: December 2009

In this review paper, the macro and microcharacteristics of superplasticity will be analyzed. Based on the macroscopic features of the superplasticity, the joining of ceramics as a new application will be analyzed with special emphasis in the fabrication of functional gradient ceramics materials. Finally, the new trends as high strain rate superplasticity (HSRS) or superplasticity at low homologous temperature will be discussed.