In order to make a compositional design for glasses with large second- and third-order optical nonlinearity, second- and third-harmonic generation of various glasses were measured. For the glasses with large nonresonant type third-order optical nonlinearity, the nonlinear susceptibility increased in the glasses with high linear refractive index, high coordination number and high ionicity. Resonant type large third-order optical nonlinearity can be seen in semiconductor and metal microcrystals-doped glasses. In this case, the role of matrix glasses was significant on the third-order nonlinearity. For glasses with large second-order nonlinearity, external treatment was indispensable, thermal poling being effective to cause second-order optical nonlinearity.

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It is elucidated that the water can function to enhance the properties such as proton conductivity and spectral hole-burning of the sol-gel-derived glasses. The porous characteristic of the glasses is favorable to adsorb the water molecules in the nano-sized pores. The conductivity was represented to be proportional to the logarithm of water concentration. The glass exhibited conductivity of -170 mS/cm at 150°C, the highest conductivity of glasses, to our best knowledge, and is expected to have potential for the electrolyte of the fuel cell operating above 100°C. It was also found that he hydroxyl bonds play important effect on the spectral hole-burning of the rare-earth ions doped in the sol-gel-derived glasses.

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Although TiO₂ exhibits a small fluoride ion exchange capacity, it was found that titanium hydroxide, Ti(OH)₄, can exchange fluoride ion with large saturation capacity of 1.60m·mol/g. Although the H₂PO₄^- interferes with the F^- exchange, the amount of F^- exchange of Ti(OH)₄ was hardly changed by the coexistence of Cl^-, NO₃^-, and SO₄^2-. The capacity for F^- exchange was almost unchanged over 4 times repetition of ion-exchange and desorption and furthermore, the elution of Ti was negligibly small. Consequently, Ti(OH)₄ is expected to be a new inorganic F^- exchanger for the removal of fluoride ion from wastewater.

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The thermoelectric properties of β-SiC fabricated from rice hulls was investigated by measuring the Seebeck coefficient (α), the electrical conductivity (σ) and the thermal conductivity (κ). The synthesized β-SiC showed n-type conductivity due to the doping of nitrogen into the structure. As the nitrogen pressure increased, the absolute value of the Seebeck coefficient decreased. The electrical conductivity was found to increase with nitrogen content up to about 0.35mass%, beyond which the value remained relatively constant. A power factor of 4×10^-6W·m^-1·K^-2 and a thermal conductivity of about 8W·m^-1·K^-1 at 1000K resulted in a Z=0.055×10^-3K^-1 figure of merit.

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By performing reactive sintering of a powder mixture of ZrO₂, Y₂O₃ and WO₃ (whose particle size distribution was 10-50μ and of submicron-order), large pieces of dense Zr_1-xY_xW₂O_8-δ oxide with a negative thermal expansion coefficient were prepared. The density of the sintered specimens prepared by such a press-free process was comparable with that of similar materials prepared by processes that include molding/pressing. It was found that the partial substitution of Y³⁺ for Zr⁴⁺ was effective for promoting grain growth, resulting in an increase of density. Zr_0.98Y_0.02W₂O_8-δ sintered bodies with density of -96% of a truncated cone shape with upper diameter, lower diameter and height of -40mm, -45mm and 20-25mm, respectively, were obtained. Negative thermal expansion was observed in all Zr_1-xY_xW₂O_8-δ specimens (x=0.00-0.02), this coefficient being hardly affected by the Y³⁺ content. It was also found that only porous and fragile specimens could be prepared by using a mixture with particle size distribution of submicron order as the raw material. This was ascribed to the formation of second-order particles that tended not to sinter within larger particles.

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ZnO doped with PbO in the range of 0.5 to 5 mol% was sintered at temperatures of 1273 to 1573 K, and microstructure and current-voltage characteristics were examined. Liquid Pb-rich Pb-Zn-O phase was penetrated among ZnO grains during sintering of ZnO-PbO composites, forming a grainboundary layer. However, PbO addition prevented densification during sintering due to the high vapor pressure of liquid PbO. The current-voltage behavior of the ZnO-PbO composites was non-linear. The resistivity of the ZnO-PbO composites decreased with increasing sintering temperature and approached that of pure ZnO. The non-linear coefficient of the ZnO-PbO composites is small, and hardly depends on the PbO content and the sintering temperature.

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This study was carried out to clarify the relationship between microstructures and mechanical properties of SiC sintered with Al₂O₃ additive (1960°C for 2h and 1980°C for 4h) and with B and C additives. Fracture surface energy, γ_i, for crack initiation and work of fracture surface energy, γ_wof, for crack propagation were selected as suitable parameters for screening the mechanical properties. γ_i was measured by both indentation fracture (IF) and Chevron notch three-point bend methods. The Chevron notch method was also performed to measure γ_wof·γ_i measured by the IF method depended on the applied load and the relationship between the load and γ_i differed among specimens with different microstructures. It was found that the γ_i measured at a high load is about the same as that measured by the Chevron notch method for all the specimens. Both γ_i and γ_wof of SiC sintered with Al₂O₃ additive were higher than those of SiC sintered with B and C additives. γ_i and γ_wof of SiC sintered with B and C were about the same, while γ_wof of SiC sintered with Al₂O₃ additive was higher than γ_i. Sintering aids, grain size and morphology affected the crack propagation behavior.

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Differential scanning calorimetry (DSC) curves of negative-thermal-expansion oxide, ZrW₂O₈, were obtained under dry N₂ atmosphere. An endothermic peak and base-line shift were observed at 124 and 169°C, respectively, upon heating measurements of as-prepared ZrW₂O₈. Upon successive cooling and heating measurements, the base-line shift at 169°C was reproduced, however, the peak at 124°C disappeared in both curves. The base-line shift at 169°C corresponded to the variation of the thermal expansion coefficient due to a structural phase transition from the acentric cubic phase with the space group of P2₁3 (No. 198) to the centric phase with the space group of Pa3 (No. 205). Thermogravimetry (TG) and thermogravimetry differential thermal analysis mass spectroscopy (TG-DTA-MS) simultaneous measurement revealed that the origin of the endothermic peak at 124°C was the secession of H₂O involved with the ZrW₂O₈ specimen, whose amount was less than 1.6 mol%. It was clarified that the trace amount of H₂O negligibly affected the thermal expansion behavior of ZrW₂O₈ and that the variation of the thermal expansion coefficient around 164°C could be attributed to the λ-type transition.

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Functionally graded PMN-PT ceramics, which had a continuously varying graded composition from one surface toward the other of the specimen, were examined with respect to their dielectric property. Specimens were prepared by sintering superposed layers of green compacts of (1-x)PMN-xPT solid solutions with different values of x. The electric permittivity (ε) of single-phase (1-x)PMN-xPT ceramics showed a peak at the Curie temperature, which shifted towards higher temperatures with increasing x. On the other hand, the profile of ε vs temperature (T) for the graded PMN-PT ceramics experienced a linear characteristic. Furthermore, a flat profile was obtained by varying the volume of layers. The relative permittivity was 10000 ± 200 in the temperature range from room temperature to 120°C. In addition, the temperature coefficient of permittivity could be arbitrary adjusted by cutting the specimen diagonally.

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Ternary phase Ti₂AlC was observed in vapor-condensed products obtained through the Ar-H₂ or Ar-He thermal plasma in-flight heating of TiC micron powders containing aluminum and the subsequent rapid cooling of plasma. The Ti₂AlC phase was well crystallized, appearing as faceted particles of hexagonal morphology with sizes of 40-80 nm that coexisted with TiC_x in the vapor-condensed products. The fraction of the Ti₂AlC phase increased significantly with an increasing hydrogen concentration in the Ar-H₂ plasma. This work demonstrates that the ternary Ti₂AlC phase can be produced via a high temperature vapor-condensation process.

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Residual stress field around a Vickers diamond indentation was studied in three commercial glasses with different strain points (T_s=635°C, 570°C and 511°C, respectively). The basis of the experimental technique is to use cracks from a small indentation as a microprobe to measure the residual stress at a specific point around a large indentation and to study the change of the residual stress by heat treatment. Residual tensile and compressive stresses around a large indentation produced by applying the load of 19.6N were distributed up to a distance of about 400μm from the indentation center. For all specimens, the tensile and compressive stresses were about 10 MPa and -50MPa--30MPa, respectively, at a distance of 200μm from the indentation center. The residual stresses decreased by heat treatment at temperatures as low as 300°C below the strain point and became zero by keeping the indented specimen at temperatures close to the strain point of each glass, for 7.2ks. The resistance to decrease in residual stresses against temperature was in the order Si-B-Al-O(T_s=635°C)>Si-Al-O(T_s=570°C)>Si-Ca-Na-O(T_s=511°C) glass. The results were discussed based on the difference of the mobility of constituent ions and flow of glasses.

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Stability of aqueous suspensions of yttria nano-sized particles prepared with Polyethylenimine (PEI) of three different molecular weights (M_w), 1800, 10000 and 70000, was investigated. Stability of the suspensions as a function of time was estimated by a viscosity measurement and infrared absorption spectroscopy (FT-IR). The highest stability was observed for the suspension prepared with PEI of M_w 10000. Isoelectric point of yttria was increased from 8.4 to 10.0 by PEI adsorption. PEI effectively works on the yttria particles not only to give positive surface charge but also to suppress hydration in aqueous solvent. Positively-charged yttria particles by PEI modification were deposited on a cathode by electrophoretic deposition and dense thick layer was successfully obtained.

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The densification behaviors in compaction and sintering processes of tiles having two layers of powders were simulated by the viscoplastic finite element method. The shrinkage strain-rate and the flow stress of the powders during the sintering required as material constants for the simulation were measured from a simple compression test with constant load. The occurrence of sintering fracture was predicted from the difference of volumetric strain calculated by the finite element simulation. The critical difference of volumetric strain for predicting the occurrence of sintering fracture was obtained from a three-points bending test during the sintering. The accuracy of the simulation was improved by using the flow stress with strain-rate and temperature sensitivities and the shrinkage strain-rate history.

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Ceramic matrix composite (CMC), made by a processing technique using a polymer impregnation and pyrolysis method, was evaluated environmentally under thermal exposure. After thermal exposure simulating practical use in the future space vehicles, the material possessed approximately 80 to 90% of the strength at ambient temperature and showed no reduction in strength at a high temperature of 1673 K. Trial parts using the present CMC material were fabricated successfully to the shape of a TPS flat panel and a leading edge curved panel. Although the density of the trial parts increased with increasing densification cycle and slightly smaller than a flat panel, the integrity was confirmed by an ultrasonic NDI method. Furthermore, the trial parts had sufficient strength as a structural component and the strength and fracture morphology were predicted reasonably by a FEM analysis using the material data resulted from coupon size specimens. Therefore, it was concluded that the CMC material had potential as candidate of structural heat resistant material for space re-entry vehicles.

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Ferroelectric material of SrBi₂Ta₂O₉ consists of (Bi₂O₂)²⁺ layer and peseudoperovskite block, (SrTa₂O₇)^2-. The crystal structure, defect, oxygen nonstoichiometory, and ferroelectric properties change by heat treatment. In this study, we investigated the relation between crystal structure, physical properties and ferroelectric properties by various heat treatment of Sr_1-xBi_2+xTa₂O_9-δ (x=0, 0.2). From the results, the remanent polarization (P_r) and coercive field (E_c) increase by heat treatment at x=0. On the other hand, P_r is almost constant and E_c decreased with heat treatment of oxidation direction at x=0.2. The dielectric constant (ε_s) increase with heat treatment of oxidation direction and Curie temperature (T_c) decrease by heat treatment at x=0. On the other hand, ε_s decreased with heat treatment of oxidation direction and T_c decrease by heat treatment at x=0.2. From the results of structural analysis by the Rietveld method using the neutron powder diffraction data, we concluded that the distortion of (Bi₂O₂)²⁺ layer and TaO₄ plane, and tilting angle of TaO₆ octahedra on a-c plane affect E_c. The tilting angle of TaO₆ octahedra on b-c plane affects T_c.

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A new fabrication method involving pulsed electric current heating was used to investigate shortening the time and lowering the cost of fabrication of silica glass. The advantages of this technique on the functionality of silica glass are also discussed. Silica powder was filled in a graphite mold having a diameter of 20mm. The temperature on the external mold surface was raised from 1773 to 1873K at heating rates of 50 and 100K/min under a constant uniaxial pressure of 20MPa. As a result, transparent silica glass free of bubbles was successfully fabricated at the heating rate of 50K/min. However, in the case of 100K/min, crystalline particles were formed on the bulk surface in addition to numerous bubbles. These crystals are attributed to a high temperature gradient, so that the heating at the bulk surface is insufficient and the temperature does not reach the melting point of silica. Investigation of the physical, mechanical and optical properties revealed that amorphous silica obtained by the pulsed electric current heating technique has the same density, refractive index, elastic modulus and absorbance as fused silica.

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When the synthesis of a yet thinner layer of Ni electrode paste is considered, the shrinkage rate of the Ni electrode paste film must be close to that of a dielectric green sheet. However, the shrinkage rate of Ni electrode paste film synthesized by the WCP or CVD method without any additive is far from that of a dielectric green sheet. Under this circumstance, the use of BaTiO₃ organometal resinate, which has the same composition as ceramics, as an additive is examined. The result indicates that it is possible to suppress sintering of the Ni electrode paste film by adding BaTiO₃ organometal resinate, compared to that without such addition; as a result, the shrinkage rate approaches that of a dielectric green sheet. Furthermore, the resistivity of the Ni electrode paste film with BaTiO₃ organometal reginate is lower than that of film without the additive. The results of this study, as discussed above, have clarified that Ni paste with added BaTiO₃ organometal reginate has superior electrical characteristics.

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We introduce metal complexes used to synthesize metal-oxide phosphor. Eu: BaMgAl₁₀O₁₇ powder was obtained by thermal decomposition of a mixture of xEu, (1-x)Ba, Mg and 10Al-EDTA complexes formed by a spray-dryer with metal-EDTA solution at the decomposition temperatures of >600°C. Blue emission was confirmed from the Eu: BaMgAl₁₀O₁₇ powder fired at 1400°C in reduction atmosphere under the flow of 4%H₂+96%Ar gas mixture.

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