Bi_1.84Pb_0.34Sr_2.03Ca_1.9Cu_3.06O_y bulk superconductors were prepared by hot press sintering at 780°-820°C at 4.9MPa-24.5MPa in air for 2h. The relationship between the porosity (p) of the sample and hot pressing conditions was empirically formulated using the following equations, ln(p)=-3Pt/(4η)+ln(p₀), η=η₀exp(E/RT), where P is the hot pressing pressure, t is the hot pressing time, η is the viscosity, p₀ is the porosity of the compact body, E is the activation energy for viscous flow and T is the temperature. The values of η₀ and E were evaluated to be 80Pa⋅s and 184kJ/mol, respectively. With increasing bulk density, the resistivity at room temperature decreased and the critical temperature of each grain, which was evaluated from the temperature dependence of magnetization, decreased. The temperature dependence of resistivity greatly differed among samples with various bulk densities. The critical current density increased with increasing bulk density. The relationship between these superconducting properties and the bulk density was explained in terms of the two factors, that is, the increase in grain coupling strengths and the decrease in oxygen content, which were caused by the densification of the sample.

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The role of stacking faults in the 3C→4H phase transformation in SiC was investigated by employing powder samples having different initial stacking fault densities and by intentionally adding 5mol% Al to suppress the effect of inherent impurities. The Al addition induced the predominant formation of 4H-polytype, and the grown 4H grains appeared to have a platelet shape. Stacking faults present in the 3C phase served as nucleation sites for the formation of 4H-polytype, but the rate of 4H growth after nucleation was higher in 3C-SiC having a smaller initial stacking fault density. Roles of stacking faults in the phase transformation and its mechanism are discussed.

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Glass formation in halide systems based on AgX (X=Cl, Br or I) has been investigated. Glasses were obtained for two- to four-component-systems containing 45-60mol% of AgX and other components such as KX, CsX, BaX₂ and PbX₂. The glass transition temperatures of AgCl-based and AgBr-based glasses were close to room temperature, while those of AgI-based glasses were about 50°C. Infrared absorption spectra of an AgI-based glass showed that the glass is rather moisture sensitive and that the cut-off wavelength is expected to be longer than 30μm. Characteristics of the glass-forming systems based on AgX and other monovalent metal halides which have been already reported, i.e., LiX and CuX, have been discussed also.

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High-quality Ba_1-XK_XBiO₃ superconductors with a T_ce of 28.5K were successfully synthesized using the plasma-arc melting and rapid-quenching (PMQ) method. X-ray powder diffraction data showed a single Ba_0.6K_0.4BiO_X structure with a lattice constant of a=4.283Å. The highest relative density was 97% of the theoretical density. Furthermore, the fabrication of an Au/MgO/Ba_1-XK_XBiO₃ tunnel-type junction was attempted on the PMQ-processed Ba_1-XK_XBiO₃ substrate. In I-V characteristics of Au/MgO/Ba_1-XK_XBiO₃ junctions, non-linearity was clearly observed at about 3mV corresponding to the energy gap of Ba_1-XK_XBiO₃ supercon ductors. It was found that the PMQ-processed Ba_1-XK_XBiO₃ is more effective for some device applications than the powder samples produced by solid state reaction methods.

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Monolithic Y₂O₃-doped zirconia gels were successfully prepared from zirconium alkoxide and yttrium nitrate hydrate. Crystallization behavior of these gels depended upon the concentration of Y₂O₃. Namely, ZrO₂ gel monoliths with 3mol% Y₂O₃ or less crystallized to tetragonal phase at 400°C. On the other hand, higher concentration of Y₂O₃ resulted in the crystallization of cubic phase at 400°C. Tetragonal to monoclinic phase transformation occurred when the Y₂O₃ concentration was below 2mol%. Doping of Y₂O₃ more than 3mol% or 8mol% stabilized the tetragonal or cubic phase on the further heating. The lattice parameters of the resulting tetragonal or cubic ZrO₂ showed that the Y₂O₃ concentration of the resulting ZrO₂ polycrystal was in good agreement with the batch composition. Translucent monolithic zirconia polycrystals were obtained by the careful heat-treatment of the gels up to 1000°C.

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Lead nitrate, magnesium nitrate and niobium oxalate as raw materials were chosen and dissolved into distilled water with nitric acid. The mixed solution was sprayed with an ultrasonic atomizer and transported into an electric furnace heated at 750°C by the carrier gas of the composition N₂:O₂=4:1. The powder, the pyrolysis product, was collected in a filter paper by pumping. The obtained powders consist mainly of pyrochlore and a little PMN. A powder of single PMN phase was obtained by calcination of as-pyrolyzed powders at 750°C. The particles had spherical shape with a narrow size distribution and an average size of 0.36μm.

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An experiment was conducted with reactivity of ZrSiO₄ sintered bodies fabricated from synthesized high-purity ZrSiO₄ powders for alkaline glass (2Na₂O⋅SiO₂) melts and change of their microstructure at 900°-1400°C. As evaluation of corrosion, comparison of the change of the weight loss and the corrosion depth of the ZrSiO₄ sintered bodies with high-purity was made with zirconsand sintered bodies and ZrSiO₄ sintered bodies with which treatment was performed by means of HIP. The corrosion reaction of three kinds of sintered bodies was liable to be governed by the melterosion mechanism, and it was known that the corrosion rate was dependent upon both purity and density of the ZrSiO₄ sintered bodies. From the result of the comparison of TZP bodies with mullite sintered bodies, it was explained that the TZP bodies were corroded very hard. With respect to the mullite sintered bodies, 2Na₂O⋅SiO₂ melts severely dissolved them. It was ascertained that it was very important to heighten the density of the ZrSiO₄ sintered bodies and to lower the reactivity with 2Na₂O⋅SiO₂ melts in order to heighten the stability in the 2Na₂O⋅SiO₂ melts. It was ascertained that it was likewise very important to heighten the stability of the ZrSiO₄ at high temperatures by augmenting the purity of the ZrSiO₄.

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Ceramic TiB₂ composites with up to 40wt% ZrO₂ or 2mol% Y₂O₃-ZrO₂ were fabricated by hot isostatic pressing (HIP) with glass encapsulation. The effect of addition on the mechanical properties and microstructure of TiB₂ HIP'ed bodies was investigated. The addition of ZrO₂ or 2mol% Y₂O₃-ZrO₂ was very effective in improving the 3-point bending strength of TiB₂. The 3-point bending strengths of TiB₂ containing 10wt% ZrO₂ and 10-20wt% (2mol% Y₂O₃-ZrO₂) were 1160-1200MPa, which were about three times higher than that of monolithic TiB₂ (450MPa). The 3-point bending strength was dependent on the monoclinic ZrO₂ ratio (monoclinic ZrO₂/monoclinic ZrO₂+tetragonal ZrO₂) and the monoclinic ZrO₂ content in the HIP'ed bodies. To obtain HIP'ed bodies with strengths higher than 1000MPa, the ratio of monoclinic ZrO₂ must be less than 60% and the monoclinic ZrO₂ content must be less than 10wt% in HIP'ed bodies. Vickers hardness and fracture toughness were also affected by the addition of ZrO₂ and 2mol% Y₂O₃-ZrO₂. The Vickers hardness of HIP'ed bodies decreased with increasing ZrO₂ and 2mol% Y₂O₃-ZrO₂ content. On the other hand, the fracture toughness increased linearly with increasing ZrO₂ and 2mol% Y₂O₃-ZrO₂ content. The fracture toughness of TiB₂ containing 30wt% ZrO₂ was 8.2MPa⋅m^1/2. This toughning was caused by crack deflection, however, stress induced transformation was not observed. TEM observation showed no grain boundary phase which was resulted from the reaction between TiB₂ and ZrO₂. However, EDS analysis showed that Ti and Zr existed in the ZrO₂ and TiB₂ grains, respectively, indicating that diffusion occured between TiB₂ and ZrO₂.

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Zirconia films were prepared by the CVD method using thermal decomposition of zirconium-tetra-i-propoxide with He gas under 20kPa. The films on the substrate consisted of fine particles less than 1μm and were metastable tetragonal-zirconia. The maximum deposition rate was 6nm/s at 673K and a reactant gas concentration of 0.05mol%. The profile of deposition rate was calculated using a simplified reaction and coagulation model. The calculated results showed a good agreement with the experimental data under the operating conditions of 673K and 0.07mol%. Deposition rates for the system used are estimated with this model.

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The processing of porous silica bodies was investigated by the consolidation and sintering method using spherical silica particles. Monodispersed silica particles with various diameters were consolidated by dry pressing, slip casting, colloidal pressing and sedimentation. Pore size was directly proportional to particle size in all four consolidation methods. Pore diameter of porous glass can be easily controlled by changing the particle size. The consolidation and the sintering conditions were found to be the essential factors in terms of the porosity, the pore distribution and the pore size of sintered bodies.

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Fracture toughness (K_IC) and crack extension resistance (R-curve characteristic) were evaluated for α-alumina polycrystals with different grain sizes. The K_IC values were measured by the SEPB and IF methods (JIS R 1607). The K_IC for a polycrystal with a large grain size measured by the SEPB was about 1.5 time as large as that measured by the IF method. The deviation of the K_IC decreased when the pop-in crack in the specimen used for the SEPB test was cut off by saw notch leaving only its front portion. Therefore, the large value of the K_IC obtained by the SEPB method for a polycrystal with a large grain size was due to the fracture surface traction behind the front portion of the pop-in precrack. The SEPB and SEVNB specimens of alumina with a large grain size were also provided for a stable fracture test in bending, and their R-curve characteristics were obtained from load-deflection curves during fracture. As unstable fracture often occurred during the bend test, a pair of elastic rectangular specimens without notch or precrack were placed on both sides of and parallel to the test specimen to improve the stability of the fracture process. The K_I0 at the initiation of the crack was determined from the point where the compliance change of the specimen and AE occurred during the bend test. The result suggested the K_IC values were overestimated when the SEPB method was applied to R-curve materials.

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A Limiting current type plane oxygen sensor with a unique structure, different from the conventional limiting current type oxygen sensor, has been developed. This sensor has cathode and anode of Pt on the same plane of ZrO₂ electrolyte, and the cathode also serves as a hole to limit gas diffusion. An investigation was made to verify the humidity sensing characteristic of this sensor above 100°C. This sensor detects humidity linealy proportional to a water vapor pressure of 0 to 450 mmHg in a wide operation temperature range from 20° to 300°C. No deterioration was observed after 10, 000 h life test.

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Surface grinding resulted in the crystallographic texture change of TZP. The intensity of (002) peak from the surface in an X-ray diffraction pattern increased significantly on grinding the surface of TZP, while that of (200) peak decreased. Similar phenomena were observed on the (113) and (311) peaks but not on the (202) and (220) peaks. The intensity enhancement of the (002) peak indicates that many small crystallites or domains in the near-surface region reoriented themselves upon grinding in such a way that their c_t axes become orthogonal to the surface. On the other hand, pole figures on (200), (311) and (220) peaks showed that the three dimensional region where the exchange between a_t axes and c_t axes occurred by grinding, and their c_t axes reoriented to the preferred orientation only when grinding was carried out to a certain limited direction against original crystal orientation.

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In forming a glass container by the blow-blow method, parison is formed in a blank mold by air blow. It is then blown in a blow mold and inflated to form a bottle. Since the final shape of a bottle is designated from the beginning, the final wall thickness of a bottle is controlled by the shape and the wall thickness of an intermediate product parison. In this way the design of parison is important, but it is difficult to study how parison is formed as glass materials to be formed are extremely hot. With this in mind, the author used silicone oil in place of high-temperature glass and measured temperature at which parison is produced and the wall thickness of parison being produced. The author also studied, from the calculation of glass flow, the relationships between variations in equal temperature distribution and temperature of parison and the wall thickness of parison. In addition, the author studied causes of bottom wall thickness and waved faults and countermeasures to be taken. The result is that we have reached the following observations: (1) The wall thickness of parison from its mouth to gob line is closely related to the flow velocity of glass material and is nearly proportionate to the parison diameter. (2) Variations in the temperature distribution of parison according to glass temperature, mold temperature and the length of time during which glass stays in a blank mold cause the flow velocity of glass material to change which in turn affects the wall thickness of parison. (3) The wall thickness of the bottom below the gob line decreases or increases depending upon the length from the gob line to the bottom of parison (the surface area of glass in contact with the mold).

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The reactivities of Ba₂YCu₃O_7-x with BaZrO₃ and CaSiO₃ were studied to develop a substrate material for superconducting oxide films. It was found that BaZrO₃ and CaSiO₃ were less reactive to Ba₂YCu₃O_7-x and the onset critical temperature of Ba₂YCu₃O_7-x remained unaltered after heating in contact with these materials at 1223K. Although BaZrO₃ was less reactive than CaSiO₃, BaZrO₃ was unsuitable for the substrate of Ba₂YCu₃O_7-x films because of the large difference of the thermal expansion coefficient. On the other hand, the thermal expansion coefficient of CaSiO₃ is almost the same as that of Ba₂YCu₃O_7-x. High-T_c superconducting oxide films were prepared easily on the CaSiO₃ substrate by the conventional dipping-pyrolysis method. As a result, mixed oxide, CaSiO₃, is one of the promising materials for the substrate of Ba₂YCu₃O_7-x films because of its low cost, low reactivity, and comparable in thermal expansion coefficient.

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Internal friction peaks in XNa₂O⋅(1-X)B₂O₃⋅2iSiO₂ glasses (X=0.3, 0.45, 0.6, 0.7, 0.75, 0.8, 0.9, 1.0) were studied in torsional vibration in the frequency range 0.35-0.8Hz. The influence of Na₂O content on the height of low-temperature peaks and the origin of high-temperature peaks were discussed on the bases of Dell's model on the structure of alkali borosilicate glass, and a method for the determination of the activation energy within a reasonable accuracy was developed. It is concluded that, on the glasses with X≤0.8, sodium ions bounded to BO₄ tetrahedron, BO₃ triangle and SiO₄ tetrahedron make different extent of contributions to the height of the low-temperature peak and that the movement of non-bridging oxygen in BO₃ triangle under stress is responsible for the high-temperature peak. The activation energy for the high-temperature peak was determined within a probable error of 6% by the approximation of the high-temperature peak and frequency curve with an equation including terms up to fourth order, and the background of the peak with an equation including terms up to third order.

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The effects of HIPing on the defect size distribution and the mechanical properties of ceramics were examined. Specimens of Y-TZP were HIPed under several conditions. Microstructures of the specimens were observed by SEM. The defect size and number were directly measured by transmission optical microscopy. The fracture toughness was measured by SEPB method. In all specimens, larger number of defects exist in the range of smaller defect size. Total number of defects and the largest defect size were reduced by HIPing. However, even in HIPed specimens, there are a few defects having several tens micrometers long. The fracture origin appeared to change from the bulk defects to the surface ones with reduction of the total defect number and the largest defect size by HIPing.

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Fine mica crystals (1-2μm) were precipitated by reheating glasses in the system Ba_0.5Mg₃(Si₃AlO₁₀)F₂-Mg₂Al₄Si₅O₁₈-Ca₃(PO₄)₂. This glass-ceramics were two times stronger (≈350MPa in bending) than conventional mica-containing glass-ceramics. The glass-ceramics contained two types of mica crystals, i.e., calcium-rich type and barium-rich type. MgF₂ in the glass compositions was effective to increase the content of the barium-mica crystal. It was found that barium-rich mica crystal effectively deflected cracks to improve mechanical strength, and that calcium-rich mica crystal generated the ease of machining.

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In order to estimate green density from forming condition and powder properties, uniaxial pressing was studied. Many kinds of high purity alumina powders were used as sample. They have different crystal phases and were made by many production process. As-received powders were pressed after added with a certain amount of water, and powders which were milled, spray dried were also pressed. Sample powders were evaluated by specific surface area, particle size, bulk density, tap density, XRD and TEM observation of the primary particles. The green density was analyzed by the powder properties and the following results were obtained. (1) The experimental equation connecting the green density and the pressing pressure was reconfirmed. Two constants in the experimental equation can be correlated to the tap density, and the estimated green density by the empirical equation agreed well with the experimental one. (2) Powders having round or bulky primary particles are compacted well without powder preparation, but the densification can be hardly improved by the powder preparation, such as milling and spray drying, on the contrary, powders having dendritic primary particles are not densified, but the powder preparation is effective to improvement of densification. (3) The relationship between the green density and the pressing pressure become straight lines which pass through one point on semilogarithmic graph, if the crystal phase of powder is the same.

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In order to synthesize well-crystallized magadiite and kenyaite as a single phase in a short reaction time, amorphous silica was hydrothermally reacted with alkaline solutions in the temperature range from 150°C to 200°C. From a suspension containing SiO₂ and NaOH with molar ratios of H₂O/SiO₂=18.5 and NaOH/SiO₂=0.23, magadiite was formed after a reaction time of 48 h at 150°C or after 18h at 170°C. The formation of Na-kenyaite, however, required 6h at 200°C. Then, KOH and K₂CO₃ were used to lower the formation temperature of kenyaite. K-kenyaite was synthesized after 16h at 185°C from a suspension with molar ratios of H₂O/SiO₂=18.5 and KOH/SiO₂=0.23. Furthermore, (Na, K)-kenyaite was formed after 48h at 150°C or after 24h at 170°C from suspensions with molar ratios of H₂O/SiO₂=18.5, NaOH/SiO₂=0.23 and NaOH/K₂CO₃=0.95-23. Magadiite and kenyaite were formed through a difinite induction period after dissolution of amorphous silica.

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A liquid phase reaction was adopted to prepare a SiC precursor. SiC powder was obtained by the pyrolysis of the precursor prepared by Würtz-Fittig reaction between silicon tetrachloride and methylene chloride using sodium naphthalene as a reducing agent. The precursor crystallized to β-SiC at 1200°C. However, the SiC was never obtained from the reaction in the silicon tetrachloride-carbon tetrachloride system. The precursor prepared from the dichlorodimethylsilane-methylene chloride system vaporized on pyrolysis. These results suggest that SiC formation by Würtz-Fittig reaction must satisfy the following prerequisites; (1) Carbon chloride should react with sodium to form anion species. (2) The precursor should have a three dimensional structure.

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To study the effects of the fictive temperature, T_f, and the OH-group on the refractive index, n, of silica glass, several samples were prepared containing from 680 to 850wt ppm of OH-group in different distribution patterns. Trimethoxymethylsilane was used as a raw material and hence the samples contained no detectable chlorine, whose inhomogeneous distribution was an important factor affecting local change of n for commercial silica glasses. For a sample with homogeneous OH-group distribution, the distribution pattern in n after stress free annealing was determined by measuring the local deviations in n, Δn, with a laser interferometer. The distribution pattern was considered to be due to the distribution in T_f. The Δn distributions observed for the annealed samples with various OH-group distribution patterns agreed well with those calculated as a simple summation of the Δn due to the local deviation in OH-group, i.e. Δn=-1×10^-7/ΔOH (wt ppm), and the Δn due to the local deviation in T_f. A way to manufacture silica glass with sufficiently homogeneous refractive index distribution was discussed.

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The thermal decomposition of Lanthanum (III) tris (malonato) chromate (III) hexahydrate (La[Cr(CH₂(COO)₂)₃]⋅6H₂O) was studied from room temperature to 1000°C in order to investigate the formation process of perovskite-type oxides. The starting material and the decomposition products in plateau ranges of 150°-250°C, 400°-470°C, 560°-680°C and 720°C- were characterized by IR and X-ray diffraction analyses. The complex compound released almost all water molecules at about 200°C. Then, the anhydrated complex began to decompose at about 250°C, and the mixed oxide (LaCrO₄) and perovskite-type oxide (LaCrO₃) formed between 560° and 680°C and above 720°C, respectively. The specific surface area and particle size of the oxide (LaCrO₃) calcined at 750°C were 2.4m²⋅g^-1 and 0.2-0.5μm, respectively.

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LiNiO₂, LiNi_1/2Co_1/2O₂, and LiCoO₂ were prepared and characterized by XRD and FT-IR. XRD data for these three samples indicated that lithium ions were located at octahedral 3 (b) sites and transition metal ions at 3 (a) sites in a cubic close packed oxygen array (space group; R3m). XRD and IR methods to estimate the degree of contamination of rock-salt domain in the solid matrix were described. Electrochemical examinations for the well-characterized samples were also carried out in lithium nonaqueous cells. These three samples exhibited 130-140mAh⋅g^-1 of rechargeable capacity in the working voltage above 3.5V with charge/discharge coulombic efficiency of ca. 97%. The key technology to establish 4-volts secondary nonaqueous lithium cells was briefly described together with a concept on the active material design based on the lithium-transition metal-oxygen ternary phase for a secondary system therefrom.

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A novel and promising method for the detection of chemical molecules in a liquid was realized using a contact of p- CuO and n-type ZnO semiconducting ceramics (p-n contact). When this device is soaked in an alcohol, a characteristic current-voltage (I-V) relation is observed. It is possible to discriminate the chemical species and to estimate the alcohol concentration in alcohol-water solutions. Since the characteristic I-V relation occurs from chemical interaction between alcohol molecules and semiconductor surfaces at the contact interface, the p-n contact is expected to be applicable for the detection of other chemical molecules in a liquid- or gas-state.

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