A single crystal of Bi_1.94Pb_0.06V_0.9Co_0.1O_5.32, in which the Bi and V sites of layer-structured Bi₂VO_5.5 were substituted simultaneously, was prepared for the first time and the effects of the Pb substitution on the conductivities in a(b)- and c-axis directions were investigated. Any improvements of ionic conductivity along c-axis perpendicular to the (Bi₂O₂)²⁺ layer was not observed compared with that in single crystal without Pb substitution. From the results of conductivity and Rietveld refinement of XRD pattern, oxygen vacancies generated by Pb substitution were suggested to locate in the pseudo-perovskite block, not in the (Bi₂O₂)²⁺ layer.

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Grain growth of AlN-TiN composite ceramics was studied under conditions where the AlN/Al₂O₃/Y₂O₃ grain boundary phase is presumed to be liquid. It was found that the growth of AlN grains was strongly inhibited as the level of TiN additions increased. Compared to AlN, TiN particles showed very little grain growth under the conditions studied. AlN grain growth in both monolithic and composite systems proceeded at a rate of one-third the sintering time, and it was postulated that AlN grain growth proceeded by the “solution-reprecipitation” mechanism. Microstructure observation showed that TiN particles were present at grain boundaries and within AlN grains. Heat treatment of the composite resulted in a severe microstructural change in which the grain boundary phase was isolated at triple points of AlN grains. Computational studies of grain growth in the presence of both, a liquid phase and dispersoids, similar to the AlN-TiN composite system, were undertaken using Monte Carlo simulation based on the Potts model. The simulation effectively expressed the dependency of grain growth on the size and amount of dispersoid as well as predicting the inclusion of dispersoid particles into matrix grains. Adjusting the γ_sl/γ_ss value from 0.5 to 1.0 yielded microstructural changes that were similar to those observed upon annealing experiments.

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The zeta potential of Tl₂Ba_1.6Sr_0.4Ca₂Cu₃O_10+y (Tl-2223) superconducting oxide particles in a cyclohexanone bath with added I₂ was studied with respect to the ionic strength, the amount of adsorption of H⁺ on the particles and the electronegativity of the metal ions in the particles. The surface charge density of particles and the ionic strength of the bath were calculated from the amount of H⁺ generated due to the addition of I₂ to the bath and the conductivity change resulting from the addition of the Tl-2223 powder. The zeta potential derived from the surface charge density and the ionic strength is in good agreement with that measured by the electrophoresis method. The ionic strength obtained from the maximum amount of deposit is in good agreement with the that obtained from the maximum zeta potential. It is shown that the amount of adsorption of H⁺ on the particles is influenced by the electronegativity of the metal ions in the particles.

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Lead zirconate titanate (PZT) thin films with various compositions near the morphotropic phase boundary were prepared on Pt (111)/Ti/SiO₂/Si substrates using a chemical solution deposition (CSD) process. The formation conditions of the thin films with a single-phase perovskite were systematically investigated by varying the processing parameters. It was found that the PZT thin films pyrolyzed at 350-500°C and then fired at 700 and 750°C consisted of a single-phase perovskite, whereas a microcrystalline pyrochlore phase remained in the perovskite matrix when the thin films were fired at 600 and 650°C. No appreciable improvement in the dielectric and the ferroelectric properties was found by increasing firing temperature from 700 to 750°C, but the leakage current density of the thin film fired at 750°C is about three orders of magnitude higher than that of the thin film fired at 700°C. The optimal firing temperature was determined to be 700°C, single-phase perovskite being obtained with optimum dielectric and ferroelectric properties as well as a low leakage current. The Pr are around 38-46, 30-40 and 25-30μC/cm² and the coercive field to 141-192, 119-136 and 80-95kV/cm, respectively, for the Pb(Zr_xTi_1-x)O₃ (x=0.45, 0.53 and 0.6) pyrolyzed at 350-500°C for 3min and then fired at 700°C. The orientation of the PZT thin film can be controlled by a pyrolysis process rather than by the firing temperature and the composition of the precursor solution. The PZT pyrolyzed at 400°C tends to take ‹100› orientation, whereas the counterpart pyrolyzed at 350, 450 and 500°C have a strong ‹111› dominating orientation.

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SiC membranes were prepared by chemical vapor infiltration (CVI) onto γ-Al₂O₃-coated porous α-Al₂O₃ tubes. Source gases of SiH₂Cl₂ and C₂H₂ diluted with hydrogen were alternatively supplied to the porous tube during heating at 800-900°C, and evacuated after the cycles through the porous tube. According to this process, SiC could be infiltrated into porous alumina. The SiC infiltration was successfully controlled by repeated cycles of the alternating gas supply. The volume of gas, permeated into the porous tube, decreased with increasing number of infiltration cycles. The SiC membrane showed hydrogen parmeances of 1×10^-8mol·m^-2·s^-1·Pa^-1 with selectivity of 3.36 over nitrogen at 350°C.

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The preparation of the γ-AlON ceramics has been carried out by a reaction sintering process. Mixed powder compacts consisting of Al₂O₃ and AlN were heated in N₂. The lattice parameters of the γ-AlON, which were obtained from the compacts by heating at 1850°C for 2h, linearly changed from 0.7939 to 0.7953nm for the composition range from 68 to 78mol% Al₂O₃ in the starting mixture. Dense γ-AlON ceramics were obtained by sintering the compact with Y₂O₃, however their bending strength was lower than that of specimens without Y₂O₃. γ-AlON ceramics with various N/O ratio, prepared from 0.25mass% Y₂O₃-containing compacts with various ratio of Al₂O₃ and AlN, were characterized with respect to their mechanical properties. Young's modulus increased slightly with increase of N/O ratio. The relation between N/O ratio and bending strength, Vickers hardness and thermal expansion coefficient were of difficult interpretation. The oxidation behavior of γ-AlON ceramics in air was also investigated. γ-AlON ceramics were little oxidized below 1200°C. At 1300°C, the oxidation of γ-AlON ceramics was accelerated, because the cracks along the surface occurred in the oxidized layer.

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In reaction-sintered silicon carbides, usually 10-40vol% of the residual silicon phase remains after the reaction-sintered process. For this reason, the bending strength of reaction-sintered silicon carbides decreases to or below 300MPa. The raw material composition (C/SiC) and the starting particle size were optimized in order to decrease the volume fraction of residual silicon and the SiC grain size. There was a tendency for the strength to increase with decreasing the residual silicon size. The strengthening effect may be attributed to the reduced residual silicon size. A reaction-sintered silicon carbide with a high bending strength of 1000MPa could be developed by the present optimization method.

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The development of fundamental processing technologies for low friction materials under boundary and fluid lubrication conditions, as well as technologies for incorporating flexibility into these materials for application to internal combustion engine components. The objectives of this study are as follows: (1) is to develop a piston ring with new inorganic-organic hybrid materials; (2) to reduce the friction to less than 80% of that in a cast iron piston ring. In this paper, the evaluation of friction and fundamental properties with test pieces was carried out. By changing the composition of inorganic-organic hybrid materials and control of heat treatment conditions, it is possible to eliminate cracking and to make the external surface flat and smooth. The possibility is confirmed of improving the friction property by controlling the wettability of inorganic-organic hybrids by oil addition.

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Grain-size dependence of total complex permeability and complex permittivity of ferrite composites made of Ni-Zn ferrite and SiO₂ is investigated by using various raw SiO₂ powders with different grain size (average grain sizes: 29μm, 30nm, 12nm, 7nm). If the volume ratio of Ni-Zn ferrite is greater than that of SiO₂, both complex permeability and complex permittivity of the ferrite composites obey the Lichtenecker's logarithm mixed law. However, if the volume ratio of Ni-Zn ferrite is less than that of SiO₂ and the grain size of SiO₂ is sufficiently smaller than that of Ni-Zn ferrite, the frequency dependence of complex permeability agrees with values calculated by assuming a model in which the grains of the magnetic materials are individually located in the dielectric medium. These results show that the complex permeability of ferrite composites depends on the grain characteristics. The total complex permeability for the ferrite composites, whose grains are contact to each other, also obeys the Lichtenecker's logarithm mixed law.

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Phosphorous-modified titanium oxide (P-TiO₂'s) nano-crystals in anatase form were synthesized by thermal decomposition of mixtures of titanium (IV) isopropoxide and ethyl phosphate in toluene in autoclave at 300°C. These P-TiO₂'s had high rutile-transformation temperatures and maintained large specific surface areas even at elevated temperatures (550-800°C). For example, the product prepared from a mixture of Ti/P molar ratio of 19 transformed into rutile at around 1000°C, and it possessed a specific surface area of 54m²·g^-1, even after calcination at 800°C for 1h

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A three-step process consisting of formation of a carbon supersaturated layer, density improvement of diamond nucleation and film growth was used to synthesize diamond films on polycrystalline Pd substrates. The results were compared with those of a two-step process in which diamond was deposited by particle growth, and the nucleation density was 10⁷cm^-2. A uniform diamond film could be obtained on the entire substrate surface by a three-step process the nucleation density was 10⁹cm^-2. The results indicate that formation of a carbon supersaturated layer using highly concentrated methane (40%) play an important role in improving the density of diamond nucleation.

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The effect of HfO₂ addition on sintering of Si₃N₄-Y₂O₃-AlN system was investigated. Although the densification was improved by the addition of HfO₂, the behavior was divided into two types according to the selected firing temperature: below 1800°C, the maximum density was achieved with 1.5mass% HfO₂ addition; on the other hand, above 1800°C density continuously increased with increasing HfO₂ addition. This densification behavior could be explained according to phase diagrams of the HfO₂-Y₂O₃⋅SiO₂ (eutectic temperature: 1800°C) and HfO₂-Y₂O₃⋅2SiO₂ (eutectic temperature: 1600°C). As a tentative mechanism for densification, it was considered that, in the initial stage of sintering, the formation of some liquid phases with low melting point promoted densification. Then precipitation of c-HfO₂ including Y, Si elements and of HfN including O occurred. This mechanism was supported by X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive spectrometry (EDS) analysis. The phase transformation from α-Si₃N₄ to β-SiAlON was found to be enhanced by HfO₂ addition. Consequently, sintered bodies obtained from the Si₃N₄-Y₂O₃-AlN-HfO₂ mixtures were consisted of not only elongated β-SiAlON grains, and grain-boundary phases composed of Hf, Si, Al, Y and O, but also isolated spherical grains of both c-HfO₂ and HfN (200-400nm in diameter).

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Lanthanum-modified lead zirconate titanate (PLZT) thin films with a La/Zr/Ti ratio of 10/65/35 were deposited on indium tin oxide (ITO)-coated soda lime glass substrates through chemical solution deposition method. Effects of excess lead addition of 30mol% in the precursor solution and/or insertion of a lead titanate (PT) film as a seeding layer between ITO and PLZT films on the crystallization behavior of the resultant PLZT thin films were investigated by X-ray diffraction. In addition, a PbO thin film was deposited on the PT seeding layer in order to control the orientation of PLZT thin films. As a result, single phase perovskite films with ferroelectricity could be successfully deposited at 450°C. Electrical properties of the resultant films were measured.

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We evaluated the characteristics of Ni paste used for the fabrication of internal electrodes of multilayer ceramic chip capacitors (MLCs). The effect of addition of BaTiO₃ powders to Ni paste on green density and sintering characteristics of electrode films were also evaluated. A green density of electrode film increased monotonically with an increase in the amount of BaTiO₃ powder and showed the maximum value, 5.4g/cm³, at 15mass% BaTiO₃. The experimental result reversed that the added BaTiO₃ particles were located into three pocket of Ni particles up to 15mass% BaTiO₃. However, the addition of more BaTiO₃ powder (20mass%) resulted in decrease in green density of electrode film. Because an excess addition of BaTiO₃ powder may cause random packing of BaTiO₃ and Ni particles in electrode films. From the measurement of shrinkage of electrode film, it was observed that the shrinkage of electrode film decreased with an increased in the amount of BaTiO₃ powder. The electrode films with 20mass% BaTiO₃ powder showed the same tendency as monolithic BaTiO₃. The results indicated that an addition of BaTiO₃ to Ni paste prevented a sintering of Ni particles. The similar results were observed from SEM observation on the surface of sintered electrode film.

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The proton-type crystalline zirconium phosphate, HZr₂(PO₄)₃, was prepared by a thermal decomposition of NH₄Zr₂(PO₄)₃ at about 680°C, where NH₄Zr₂(PO₄)₃ was obtained in advance by a hydrothermal synthesis using a mixed solution of ZrOCl₂, H₃PO₄ and H₂C₂O₄. This zirconium phosphate was, then, mixed with other metal nitrate, M(NO₃)_n (M=Li, Na, K, Rb, Sr, Bi, Y, Mg, Ca, Sc, Mn, Fe, Co, Ni, Cu, Zn, Ag, Cd, Cs, Ba, La, Ce, Tl or Pb; n=1, 2 or 3), at room temperature. The TG-DTA curves of these mixtures showed an endothermic weight loss around melting or decomposition temperature of each metal nitrate as a component. From these results, calcination temperature, which is in the range of 500-800°C and 100-200°C higher than the endothermic peak temperature, was determined for each mixture, in order to eliminate the unreacted components. All products thus calcined gave the XRD patterns attributable to M{Zr₂(PO₄)₃}_n (n=1 for M(I), n=2 for M(II) and n=3 for M(III)) with a NASICON-type structure.

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A Selective coloration process has been newly developed utilizing photosensitive gel films derived from metal-alkoxides chemically modified with β-diketones. Photosensitive ZrO₂ gel films modified with acetylacetone were irradiated with UV-light through a mask and then SiO₂ gel films containing various dyes were deposited on them. Rinsing these bilayers with water produced positive color patterns of the mask used. The dye-containing SiO₂ gel film on the unirradiated part of the ZrO₂ gel film remained, while that on the irradiated part was removed upon rinsing. This phenomenon can be ascribed to the difference in interaction between SiO₂ and ZrO₂ gel films in irradiated and unirradiated parts.

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Ion-exchange resins with particle size of 0.5mm were treated by an aqueous solution of MgSO₄ and then they were carbonized for 1h in a nitrogen gas at the temperature ranging from 300 to 1000°C. The amount of MgO in carbon samples was about 30mass%, irrespective of carbonization temperature. The antibacterial activity of carbon samples containing MgO was examined by the colony count method. The pH values in physiological saline dispersed within carbon samples were in the range of 9.4-9.8, but the values did not affect the occurrence of antibacterial activity. From the antibacterial tests, it was found that the antibacterial activity for Escherichia coli and Staphylococcus aureus on carbon samples containing MgO increased with the increase of the carbonization temperature of the ion-exchanged resin.

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Second-harmonic generation (SHG) was observed from PbO-GeO₂ glasses after thermal poling. As in PbO-SiO₂ glasses, the compositional dependence of SHG intensity was found, although the SHG intensity was rather small. The largest SHG intensity was observed for about PbO=35mol%. On the basis of extended X-ray analysis fine structure (EXAFS) results previously obtained, it was considered that remarkable increase of SHG intensity found for PbO>20mol% was caused by the formation of non-bridging oxygens. On the other hand, then the decrease of the intensity at PbO>35mol% was due to the disappearance of non-bridging oxygens.

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Hollow alumina precursor was prepared by the enzyme-inspired precipitation onto o/w emulsion using urease. Decomposition of urea by urease increased the pH of the solution to hydrolyze aluminum sulfate. The advantages of the enzymatic reaction are that the apparent precipitation rate could be controlled by the enzyme concentration of urease, and that the precipitation could take place without the destruction of emulsion. Hollow particles were obtained at enzyme concentrations ranging between 10 and 50mg/l. The destruction of the emulsion occurred at enzyme concentrations <10mg/l while nucleation took place spontaneously in the solution at enzyme concentrations >50mg/l. Hollow powders with the phase of pseudo-boehmite, maintained their apparent shape after transformation into α-alumina at 1300°C.

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The effect of Y₂O₃ on the synthesis of AlN by the carbothermal reduction-nitridation of Al₂O₃ was investigated. The amount of Y₂O₃ addition was varied from 0 to 7.50mass%. Nitridation was carried out at 1450°C for 0-360min in N₂ flow. The grain sizes of synthesized powders were almost same regardless of the amount of Y₂O₃ addition. The synthesized AlN powders appeared round shape. From XRD analysis, Y₄Al₂O₉ was identified as an intermediate compound during nitridation. It was confirmed to be finally converted to Y₂O₃ after nitridation. Therefore this synthesized powder is considered to be advantageous to densification because the remaining Y₂O₃ acts as a sintering aid.

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Bioactive ceramics and related technologies are clearly expanding their applications in clinical bone repairs. One major direction of the current research is toward bioactive materials that overcome the poor mechanical performances of the classical bioactive ceramics. Bioactive surface functionalizations are being endeavored to prepare functionally graded bioactive ceramic surfaces on ceramics and metals with high fracture resistance. Sol-gel derivation of bioactive hybrids aims at bioactive materials with high malleability. These efforts are producing new bone-repairing materials with different mechanical functions. Biomimetic processes are being aspired to produce an uniform bonelike apatite layer on polymers with fibrous macrotextures in acellular simulated body fluid. The final goal of these processes is an apatite-polymer composite which has bonelike three-dimensional structure and consequently reveals bonelike mechanical properties. Another major area is bone tissue engineering which uses the classical bioactive ceramics such as Bioglass^®, HA, β-TCP and glass-ceramic A-W. Biological assessments imply that bioactive ceramics are optimal matrices for delivering bone cells and growth factors and stimulating their functions. These two directions may find consensus for better bioactive materials in the near future.

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Heteroepitaxial growth of Ba_xSr_1-xTiO₃ thin films and their ferroelectric properties were reviewed. Lattice misfit strain could be introduced in the heteroepitaxial films, when they were grown with rf magnetron sputtering. It was confirmed from hysteresis measurements that the Curie temperature of the heteroepitaxial films could be artificially raised to higher than 200°C. A ferroelectric hysteresis loop could be observed even when the thickness of BaTiO₃ was reduced to 12nm, which contained about 30 unit cells of the crystal in parallel to the polarization axis. Based on the results of a series of studies, it is expected that heteroepitaxial Ba_xSr_1-xTiO₃ films can be used in ferroelectric nonvolatile memories with a large-scale integration. The Ba_xSr_1-xTiO₃ films will provide chemically stable memory cells with good reproducibility and compatibility with the Si process, because they are free from volatile elements such as Pb or Bi. Further investigation and development will be required to improve the ferroelectric properties of the heteroepitaxial capacitors, especially on Si substrates.

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