The grain orientation technique, which is one of several ceramic preparation methods with a controlled grain structure during the ceramic sintering process, gives an anisotropic single-crystal-like behavior to the ceramics with lower symmetric crystal structure such as the bismuth layer-structured and the tungsten bronze types than the perovskite structure. Bismuth layer-structured ferroelectrics (BLSF) are characterized by low dielectric constant, high Curie temperature and large anisotropy in electromechanical coupling factors than those of PZT family. Further more, the characteristics can be easily enhanced by the grain orientation. This paper describes the effects of grain orientation on electrical properties such as dielectric, ferroelectric, piezoelectric and pyroelectric properties of some grain-oriented BLSF ceramics by the hotforged (HF) method, comparing them with ordinarily fired (OF) non-oriented ones.

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Near-infrared (NIR) Raman spectroscopy has shown its unique advantages for characterization of ZnS:Cu, Al materials, emitting a strong luminescence in the visible region. We demonstrate that, because of a rapid decrease of luminescence in the NIR region, Raman spectra with 752.5-nm excitation are free from the visible luminescence, which usually masks Raman signals with visible excitations. By comparing the spectra of ZnS:Cu, Al samples with different luminescence efficiencies, we also find that crystal imperfections, including coexistence of hexagonal domains, can lead to a reduction of luminescence properties.

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The influence of high temperature oxidation on the Vickers hardness of a cemented carbide, tungsten carbide (WC) added with cobalt (Co), was investigated in order to determine its suitability for improvement hardness. The Vickers hardness of WC-Co was improved by high temperature oxidation treatment. The oxidation thickness of the sample from 973 to 1273K depended on oxidation temperature and time. The oxidation thickness increased with increasing oxidation temperature and time, especially, significant oxidation of samples occurred at 1073K.

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In-situ reaction and texture development were investigated during heat treatment in reactive templated grain growth (RTGG) processing for textured SrTiO₃ (ST) ceramics. Platelike Sr₃Ti₂O₇ (S3T2) particles were used as a template and aligned S3T2 particles were heat-treated with stoichiometrically required amounts of TiO₂ for textured ST ceramics. The sintered ceramics exhibited uniaxial ‹100› orientation and the degree of orientation reached was 0.43 (Lotgering's factor). X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses revealed that an S3T2 single-crystal template was converted into an ST polycrystal with its outer shape maintained. The following grain growth mechanism of converted ST caused a marked increase in the degree of orientation.

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Moisture content is one of the most important factors governing both structure and properties of green powder compacts of ceramics made through a compaction process. To control the moisture content in powder granules, it is necessary to understand kinetic changes of moisture content in granules, and pressed compacts. The apparent diffusion coefficient of moisture was directly measured for powder compacts containing polyvinyl alcohol (PVA) by following the weight change of the specimen. The parameters examined in this paper were size of specimen, forming pressure, average relative humidity and binder content. The observed rate of change was clearly affected by the PVA content in the compact. Examination of the distribution of PVA in the granules and compacts using optical microscopy (using immersion liquid method) was found to be nonuniform. The diffusion path consisted of an alternate sequence of thin layers of PVA-rich regions and thick layers of PVA-poor regions. The PVA-rich layers had a non-homogeneous structure which contained open pores.

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Deodorizing ability of a diatomaceous material mined from Wakkanai district in Hokkaido Pref. was examined in detail. This material is widely distributed in the market as a material of environmentally-friendly inner-wallboard. Alternative introductions of a model odor {NH₃, CH₃CHO, or (CH₃)₂S} mixed-N₂ gas flow and a pure N₂ gas flow into the diatomaceous material showed reversible adsorption and desorption of the odor components at 25°C, reconfirming regeneration of deodorizing ability for the diatomaceous-wallboard by ventilation of rooms with these wallboards. The adsorbed quantities of the odors onto the diatomaceous material during one hour readily cleared the odor level 3:2.3ppm for NH₃, 0.14ppm for CH₃CHO, and 0.044ppm for (CH₃)₂S, respectively.

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The surface of an ethylene-vinyl alcohol copolymer (EVOH) was modified with Ti-OH groups by a silane coupling treatment followed by treatment with a titania solution. The arrangement of the Ti-OH groups formed on EVOH was changed from amorphous into anatase structure by a subsequent HCl solution treatment. Bonelike nanoapatite was successfully formed on the surface-modified EVOH even in a form of fibers as well as plates within 2d at 36.5°C in a simulated body fluid (SBF) with ion concentrations approximately equal to those of human blood plasma. The resultant nanoapatite-polymer fiber composite was similar to that of natural bone in its structure where apatite nanocrystals are deposited on fine organic fibers constituting a composite. Therefore, if the present surface modification can be applied to a three-dimensional fabric with a structure similar to the collagen fibers of natural bone, a composite with an analogous structure to that of natural bone would be obtained. The resultant composite is expected to exhibit mechanical properties analogous to those of natural bone, as well as bone-bonding ability, and hence be truly useful as a new bone substitute.

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Bismuth layer-structured ferroelectrics (BLSFs), M_0.5Bi_2.5Ta₂O₉ (M=Na, K) were synthesized using a solidstate reaction. Na_0.5Bi_2.5Ta₂O₉ (NBT) single phase polycrystals were obtained by heating raw material powders at 1100°C. On the other hand, K_0.5Bi_2.5Ta₂O₉ (KBT) powder contained KTaO₃ as a main impurity phase. Dense ceramics of NBT were prepared by considering Bi₂O₃ vaporization and using a binder. Result of dielectric and ferroelectric characterizations of the NBT ceramic were as follows: Curie temperature, T_C=780°C, dielectric constant, ε_s=158, dielectric loss factor, tan δ=0.011 as measured at room temperature and 1MHz and the remanent polarization, P_r=15-18μC·cm^-2. The P_r value is the largest among reported BLSFs that are composed of two perovskite layers.

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We prepare composite materials that Ag₂Te grains were dispersed in AgBiTe₂ matrices with the compositions of (AgBiTe₂)_1-x(Ag₂Te)_x. The textures depend on the composition. We measured electrical conductivity, thermal conductivity, Seebeck coefficients and Hall coefficients as a function of the composition. Eased on these data, we estimate Hall mobility and lattice thermal conductivity, and finally thermoelectric figure of merit. We show that the figure of merit is enhanced in the composite system by means of enhancement of phonon scattering at the grain boundaries.

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The effect of cold isostatic pressing (CIP) on microstructure and shrinkage anisotropy during sintering is systematically and quantitatively examined for uniaxially pressed alumina compacts made from spray-dried granules. This study helps to clarify the abnormal effect of CIP on their sintering behavior. Uniaxial pressing caused anisotropic deformation of granules in the compacts, making spherical granules into an elliptical shape and developing the arrangement structure of particles. A subsequent CIP slightly reduced the apparent deformation of granules, but increased the degree of particle arrangement evaluated by optical microscopy. It also increased the shrinkage anisotropy of the compacts during sintering. The experimental results indicated that there was a linear relationship between the degree of particle arrangement and the shrinkage anisotropy during sintering when employing the pressed alumina compacts.

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Correlation between mechanical properties such as internal friction and shear modulus and the microstructure of ALON-based composite ceramics incorporated with BN was investigated at elevated temperatures in air. Internal friction (Q^-1) of the ALON-based composite ceramics exhibited peaks, independent of the amount of BN added, at around 250-350°C, 700-750°C and 1000-1100°C, then increased monotonically at 1250°C which is the maximum temperature measured, On the other hand, by high temperature X-ray diffractometry (XRD), ALON (Al_{(64+x)/3_??_(8-x)/3}O_32-xN_x) and BN phase, and aluminum borates oxidized both, were identified as the microstructures (formed crystalline phases) formation temperatures of the phases corresponded to the three peaks of internal friction (Q^-1). However, shear modulus measured at the same time with internal friction, decreased monotonically with temperature and did not reflect any microstructural change at high temperature. Therefore, it was clarified that the microstructural evolution of ALON-based composite ceramics at high temperature, can be detected by internal friction measurement.

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The solid solution's formation and microwave dielectric properties of Bi-doped Ba_6-3xR_8+2xTi₁₈O₅₄ (R: rare earth, x=2/3) series were investigated based on the crystal structure. The crystal structure is the tungstenbronze-type like with perovskite blocks including R ions and pentagonal sites with Ba ions. Bi ions have been substituted for Ba ions in pentagonal sites at early stage in La and Nd-series. Subsequent substitutions of Bi ions occur for R ions in rhombic sites same as other Sm, Eu and Gd series. The Bi ion's substitution affects the microwave dielectric constants (ε_r) as having inflection point for La and Nd-series. In the case of other Sm, Eu and Gd, dielectric constant (ε_r) increased and the quality factor (Q⋅f) value decreased, according to the increase of y in the Ba₄(R_1-yBi_y) _9+1/3Ti₁₈O₅₄ compositions. The temperature coefficients of the resonant frequency (τ_f) has an inflection point at y=0.1-0.15 composition.

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Rare earth-doped alkaline earth silicates, Sr₂MgSi₂O₇:Eu²⁺, Dy³⁺ and Ca₂MgSi₂O₇:Eu²⁺, Dy³⁺, with an akermanite-type structure show bright and long-lasting phosphorescence. After irradiation by a white-color fluorescent lamp (780lm) for 5min, the light blue emission of Sr₂MgSi₂O₇:Eu²⁺, Dy³⁺ was observable by naked eye in the dark for over 100min after removal of the excitation light source.

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Granular and platelet-shaped gallium nitride (GaN) crystals were prepared at 600-700°C and 4-7MPa of N₂ for 24-96h by using a K-Ga melt. The granular crystals with a size of 50-80μm were a mixture of cubic zincblende-type GaN (c-GaN) and hexagonal wurztite-type GaN (h-GaN). The ratio of c-GaN in the mixture increased with decreasing temperature and with decreasing N₂ pressure. The platelet crystals obtained were h-GaN and have a size of about 1mm. A colorless transparent grain of GaN with a size of 80μm was characterized by cathodoluminescence (CL) spectroscopy at room temperature. A CL peak with a full width at half maximum of 76meV was observed at 3.209eV which agreed with the near band emission peak position reported for c-GaN thin films.

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Calcium hydroxide powder was coated with a silicon alkoxide and a chelate compound of aluminum, and heated at 500-800°C to prepare silica- and alumina-coated lime powders. Specific surface area and SO₂ absorbability of silica- and alumina-coated lime powders were higher than those of the uncoated powder. Calcium silicate and calcium aluminate formed on the surface of these powders. It was considered that the improvement of SO₂ absorbability for the silica-coated powder was attributed to an increase of specific surface area, while that for the alumina-coated powder arose from on increased acidity.

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A method for the production of 2.0mm thick tempered glass plates by using the impingement of air jets and its subsequent heat transfer was studied experimentally. Tempering degree of glass plate specimen was estimated by measuring the fragment density. It was found that 2.0mm thick tempered glass plates produced by lack-expansion flow had favorable tempering degree and also good surface condition for practical use. Heat transfer coefficient was approximately calculated by Reynolds number and nozzle stand-off distance in the condition of the lack-expansion flow instead of subsonic flow.

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Spherical mesoporous silica particles were successfully prepared upon hydrolysis of tetraethylortosilicate (TEOS) in presence of dodecylamine (DDA) as on organic template. Comparison of the products obtained by a other method and synthesis conditions were also studied. The product obtained by HMS method using DDA was more homogeneous and truly spherical as compared to that obtained by other method using dodecyltrimethylamonium bromide (DTAB) and cetyltrimethylammonium bromide (CTAB). The particle size could be modified by adjusting the molar ratio of DDA/TEOS and EtOH/TEOS of the solution, particle sizes ranging from 0.2 to 1.2μm. The surface area of spherical mesoporous silica particles 1.23μm in size was about 423m²/g, their density was 1.4g/cm³ and their pore mean diameter was 3.6nm.

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Electroconductive composites were prepared from graphite as a filler material, piezoelectric ceramics as a matrix, and epoxy resin as a binder. When the filler volume fraction was near V_c on a percolation curve, the composite exhibited a nonlinear I-V characteristics, in analogy with varistors. It was assumed that this phenomenon was due to the distortion of the piezoelectric matrix upon applying a potential through the sample.

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The reactivity of B₄C with mullite was investigated under Ar and reductive atmospheres, respectively. The results indicated that B₄C could coexist stably with mullite under Ar atmosphere below 1350°C, above which some reaction would occur to form Al₂O₃ and Al₃SiB₄₈ phases. Under a reductive atmosphere, whereas, they exhibited a relatively higher co-existing temperature of 1500°C, which is deemed to be dependent on the partial pressure of CO₂ gas in heating atmosphere. Coating technique was employed in this study to suppress the reaction between B₄C and mullite by producing a TiO₂ thin coating layer on the surface of B₄C particles. TiO₂ will react with B₄C at high temperature to produce TiB₂ and B₂O₃. The latter phase, existing on the grain boundary of B₄C particles by a liquid state at high temperature, will, together with TiB₂, serve as a barrier to inhibit the reaction between B₄C and mullite. A2mass% TiO₂ on B₄C powders can effectively suppress the occurrence of this reaction.

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A new type of composite PTC thermistor was fabricated from ZnO-varistor particles and silicone rubber. The non-ohmic varistor characteristics were held in the composites. The ZnO-varistor particles were found to behave as a conducting filler at voltage higher than the varistor voltage, The PTC effect appeared in the composites containing varistor particles with volume fraction over the percolation threshold (≥250vol%). The electrical resistivity at room temperature and the temperature region showing PTC effect varied according to the applied voltage.

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Concentration dependence of emission properties and lifetimes of Tm³⁺ doped tellurite glasses in telecommunication wavelength region were investigated. According to Judd-Ofelt analysis, it was clarified that the quantum efficiency of 1.46μm in Tm³⁺-doped tellurite glasses was almost equal to that in fluoride glasses, which were used as host materials for Tm³⁺-doped fiber amplifiers (TDFA). The emission intensity ratio of the 1.80μm band to the 1.46μm band increased with increasing Tm³⁺ content. Moreover, the lifetimes of the ³H₄ level decreased rapidly with increasing Tm³⁺ content. These results show that tellurite glass is useful as host materials of TDFA and in order to achieve a high quantum efficiency of 1.46μm emission in tellurite glasses, the concentration of Tm³⁺ should be low so that cross relaxation can be suppressed.

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The addition of sintering suppressor to Ni paste was studied in order to enable further thinning of the MLC Ni electrode. The contraction rate of the Ni paste without the sintering suppressor increased as the paste grain diameter decreased. A considerable difference was observed between the sintering contraction rate of a dielectric green sheet and that of Ni paste. This finding led us to consider that the sintering contraction behavior of Ni paste should be close to that of the dielectric green sheet in the manufacturing process of current ceramic capacitors. Therefore, we studied an organometallic acid salt with the same composition as the ceramic. According to the results of our study, sintering of electrode paste film was inhibited when using Ni paste with an organometallic acid salt in contrast to the case of using Ni paste without an organometallic acid salt. Furthermore, the study of resistivity to determine the electrical characteristics revealed that the Ni paste film with the sintering suppressor exhibited low resistivity compared to the Ni paste film without the sintering suppressor. It was clarified that Ni paste with a sintering suppressor has excellent electrical characteristics.

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