The grain growth of ZnO with Li₂O and Na₂O additions was studied and is compared with a previous report of the effect of K₂O. These three alkali oxides each decrease the rate of ZnO grain growth. Their effects on ZnO grain growth are quantitatively described in terms of the kinetic grain growth equation: Gⁿ-G₀ⁿ=K₀⋅t⋅exp(-Q/RT). The parameters are compared with similar analyses of the grain growth of pure ZnO. Apparent activation energies, Q′s, for ZnO grain growth with alkali oxide additions increase in the order: Li₂O, Na₂O and K₂O. Two ZnO grain growth inhibition mechanisms appear to be active, including: (1) alkali oxide solute segregation to the ZnO grain boundaries creating a drag mechanism that reduces the grain boundary mobility, and (2) a reduction of the cation vacancy concentration and the occupation of interstitial sites by the alkali cations in solution in the ZnO wurtzite structure. This latter mechanism reduces the rate of diffusion of Zn²⁺ during grain growth.

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Low temperature firing of 0.5wt% MnO₂-added Pb(Zr_0.53Ti_0.47) O₃ (PZT) ceramics is desirable for suppressing the volatilization of PbO. The effect of two additives, BiFeO₃ and Ba(Cu_0.5W_0.5)O₃, both with the perovskite-type structure on the sintering temperature and piezoelectric properties of the PZT ceramics has been investigated. The addition of two complex oxides lowered the sintering temperature and improved piezoelectric properties. Simultaneous addition of CuO improved the piezoelectric properties. A 0.92PZT-0.05BiFeO₃-0.03Ba(Cu_0.5W_0.5)O₃ ceramics including 0.08wt% CuO ceramics sintered at 935°C for 30min gave the following characteristics; K_p=47.0%, Q_m=950, d₃₃=236×10^-12C/N, ε^T₃₃/ε₀=850, tanδ=1.0%, T_c=290°C, and bulk density=7.66g/cm³.

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TiO₂ films, as well as powders as reference, were prepared using the sol-gel process, using titanium isopropylalkoxide (TIPT) as a precursor. The films were deposited on glass slides and heated either to 300°C or to 500°C. The morphology of the film surface was observed using scanning electron microscopy (SEM). Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS) at different relative humidities were carried out to study the possibility of using sol-gel processed titania films as detecting elements in humidity sensors. A good resistance versus relative humidity (rh) sensitivity was observed in the range from 50% to 85%rh. The response time of titania films was rather fast, estimated in a few seconds.

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Phase diagrams of the Al₂O₃-Yb₂O₃-SiO₂ system and the properties of glasses in this system were investigated. The results are summarized as follows:
(1) Phase diagram of the 3-component Al₂O₃-Yb₂O₃-SiO₂ system at 1550°C and those of the three types of 2-component Yb₂Si₂O₇-Al₆Si₂O₁₃, Al_1.25Yb_0.75O₃-SiO₂ and Al_1.44Yb_0.56O₃-SiO₂ systems were established and the region where the liquid phase exist at a high temperature was clarified. The lowest solidus temperature in the present system is 1500°C.
(2) The glass-forming region of the Al₂O₃-Yb₂O₃-SiO₂ system was clarified by quenching the melt in an infrared image furnace
(3) The glass transition temperature of the present glasses is in a range of 880-895°C. The onset and peak temperatures for crystallization are in a range of 975-1040°C and 1070-1230°C, respectively. They tend to increase as the SiO₂ concentration is increased.
(4) In the 2-component Yb₂Si₂O₇-Al₆Si₂O₁₃ system, the peak temperature for crystallization and the activation energy for crystal growth attain a maximum at a composition near the eutectic composition.
(5) Analyzing the infrared spectra of glasses, it is suggested that Yb ion is mainly a network modifier in glassses.
(6) Solidus temperature of the Ln₂Si₂O₇-Al₆Si₂O₁₃-SiO₂ system (Ln=Dy, Er, Gd, La, Nd, Sm, Y, Yb) tend to increase as the radius of rare-earth ion decreases. The system with Yb has the highest solidus temperature among them.

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Alumina ceramics containing various amounts of TiO₂ were fabricated by sintering in humid reducing atmospheres and also in air. The sintered samples were treated at various temperatures in reducing atmospheres. The electrical resistivity measurments and microstructural observation were conducted on the obtained samples to clarify the relationship between the ceramic microstructure and the resistivity. The resistivity decreased with increasing TiO₂ content and the resistivity change with addition of TiO₂ behaved as the percolation curve, when the samples were sintered in humid reducing atmospheres. However, the percolation curve disappeared and the resistivity decreased gradually with increasing TiO₂ content after the heat treatment. In order to clarify the relationship between electrical resistivity and microstructure of sintered body, EPMA analysis and X-ray diffraction were conducted. Rutile, Mg-Al-Ti solid solution and Ti in Si rich grain boundary phase were detected in the fabricated samples and Ti solid solution was also confirmed in the alumina grains. It is considered that the great decrease in the electrical resistivity, which was observed in the samples containing more than 2.0wt% TiO₂, is caused by the formation of the connections among low resistivity Ti-compounds. This microstructural change is considered to cause the percolation curve. After the heat treatment, the low resistivity Ti-compounds disappeared into microstructure. It is considered that the disconnections of low Ti-compounds increase the resistivity of sintered body.

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Demand for the improvement of the quality of X-ray CT detectors is increasing. In order to realize the requirement, Gd₂O₂S: Pr (Ce, F) scintillating powder was sintered using a HIP technique. The highest light output from a 1mm thick specimen combined with a silicon photodiode, when excited by 120kV X-rays, has reached 1.9 times of CdWO₄ single crystals. The CT equipment of the third generation type requires high uniformity among many scintillator elements. Particularly, quality response characteristic and distribution of light output is very important. In this report, parameters which have a great influence on the quality response characteristic were studied using the Kubelka-Munk theory. Agreement between calculated and experimental results was obtained, and calculated results indicated that quality response characteristic increased with increasing optical absorption coefficient, scattering coefficient and X-ray absorption factor.

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The solubility of quartz from ammonium fluoride solution was measured using a small autoclave. Based on the solubility data, a single crystal of quartz was grown from ammonium fluoride solutions at 230-280°C and 4-101MPa. The growth rate depended on the growth temperature, temperature gradient and concentration of the ammonium fluoride solution. The maximum growth rate of the Z face attained was 0.88mm/day which was comparable to that in alkaline solutions. However, the growth rate of the X face was very low, the growth rate of -X face was less than one fifth of that for +X face. Fine pyramidal growth hills were observed on Z face, and the size increased with increasing pressure and concentration of ammonium fluoride solution. The linear defect density in Z growth zone was about 10³-10⁵pcs/cm², higher than that in alkaline solutions. Strong absorption at about 3500cm^-1 by -OH stretching vibration was observed in FTIR spectra. The defects originating from -OH depended on the temperature gradient.

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Effects of the interface states on the applied voltage dependence of the double schottky barrier (DSB) are theoretically discussed. On the basis of the simplified models of rectangular density distributions for the interface states, effects of the energy level, density of states, and the distribution width of the interface states on the applied voltage dependence of the DSB were quantitatively calculated. The I-V characteristics of DSB's were also calculated and the nonlinear I-V relations were discussed. The nonlinear exponent was found to be determined mainly by the barrier height and the total charge of the interface states.

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The effect of severe HIP sintering conditions (2050°C, 180MPa) on the crystal structure and fracture behavior of SiC platelets embedded in an Si₃N₄ matrix has been examined. The starting SiC platelets were single crystals of hexagonal structure (α-SiC) mainly constituted of the 6H and 4H polytypes with a minor fraction of 15R type. Etch-pit analysis revealed that this latter structure was a host in 6H or 4H crystallites and did not exist as a single crystallite. The SiC crystallites were separated from the nitride matrix by a chemical procedure and characterized by XRD, SEM and AFM. Then, the results were compared with that by TEM and SEM on the bulk composite specimen. No phase transformations were detected and the polytype fractions were unchanged after HIP sintering. However, locally unbalanced shear forces by neighboring crystals deformed the SiC platelets plastically during sintering causing the slip of close-packed (0001) planes and resulting in the introduction of high density dislocations into the crystals by glide mechanism. The dislocation density in the SiC platelets after HIP sintering was typically in the order 10¹⁵m^-2. Dislocations had little or no effect on the cleavage fracture of the SiC platelets but produced some kinking and local splitting of the crack path for propagation along other crystallographic planes.

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Pressure enhancement due to the interaction of conically converging shock waves was experimentally investigated in a double cylindrical capsule made of materials with different shock wave velocities and shock impedance. The development of a new technique for material synthesis by using shock wave interaction and its application to the synthesis of a compound in the system B-C-N were described. A capsule for effective shock wave interaction was designed on the basis of numerical calculations by using the two dimensional hydrocode PISCES, and shock recovery experiments in such capsules were conducted for mixtures of coarse grain diamond and fine grain hexagonal boron nitride powders. Some analysis revealed that the sintering of the powders was promoted by this technique and that the distributions of searing stress and chemical components were inhomogeneous. Unknown peaks found in X-ray diffraction patterns suggested a possibility of new B-C-N compounds.

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The synthetic conditions of amorphous calcium carbonate such as initial concentration of reactant, temperature and pH in the reaction of CaCl₂-Na₂CO₃-NaOH system, and its crystallization in water and NH₄Cl solution were investigated. Characteristics of the amorphous phase were determined by means of X-ray diffraction, thermal analysis (TG-DTA), scanning electron microscopic observation and measurement of solubility. The amorphous calcium carbonate (ACC) and amorphous basic calcium carbonate (ABCC) were precipitated by adding 0.1mol⋅dm^-3 CaCl₂ solution into the mixed solution of 0-3.0mol⋅dm^-3 NaOH and 0.1mol⋅dm^-3 Na₂CO₃, and then the precipitated colloidal phases were filtered and dried rapidly through dry air under reduced pressure. The stable phases of ACC and ABCC were formed in the region of pH 11-14 at 0°C but the formation regions of both amorphous phases were remarkably affected by pH in the mother liquor. Namely, ACC was formed at pH 11.0-13.5 and ABCC at pH 13.5-14.0. Their compositions were formulated as CaCO₃⋅1.5H₂O for the former and Ca₃(OH)_6X(CO₃)_3-3X⋅3YH₂O (0<X≤0.2, 1.5>Y≥1.2) for the latter. These results show that increase of pH contributed to the partial replacement of CO₃^2- of ACC by OH^-, which resulted in the formation of ABCC with different compositions. ACC was dissolved rapidly in water and its highest solubility was 1.8×10^-4mol Ca²⁺/100cm³ H₂O, i.e. ten times larger than that of a commercial calcium carbonate (calcite-type). The dissolution of ABCC was affected by the amount of OH^- contained in the random structure and the highest solubility of ABCC with composition Ca₃(OH)_0.72(CO₃)_2.64⋅4.14H₂O was 4.0×10^-4mol Ca²⁺/100cm³ H₂O after dipping in water for 10min. The control of crystal shape and modification of calcium carbonate were investigated by dipping spherical secondary-particles of ACC in water and 1mol⋅dm^-3 NH₄Cl aqueous solution, respectively. ACC was crystallized into rhombohedral-like calcite with about 4μm in size at 20°C, needle-like aragonite with length 1-3μm and diameter 0.2μm at 80°C when dipped in water and spherical vaterite with diameter 0.5-1.5μm in 1mol⋅dm^-3 NH₄Cl aqueous solution.

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Fatigue behavior of silicon nitride ceramics under cyclic loading was evaluated by using smooth specimens. Based on the statistical method proposed by Fett and Munz, the fatigue crack growth rates (da/dN) were calculated from the fatigue lifetime distribution. The crack growth rate was accelerated by humidity of ambient air. In a dry nitrogen, the crack growth rate did not depend on the frequency, however, it was retarded by small stress amplitude. According to the fracture toughness data measured by a controlled surface flaw method, the bridging effect in smooth specimens was not significant. It is deduced that stress corrosion cracking (SCC) is one of the important mechanism in fatigue crack growth of silicon nitride ceramics. It is supposed that the cyclic loading in silicon nitride ceramics causes damage to bridging zone and/or other fatigue crack growth mechanism such as initiation and coalescence of microcracks.

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Spherical LiCoO₂ fine powders were prepared by the ultrasonic spray decomposition. The effect of synthesis factors on particle morphology, particle size and its distribution, and crystallinity was investigated. LiCoO₂ was obtained by the spray decomposition at 500°C. Asprepared powders were porous and nonagglomerated particles with sub-micrometer sizes having narrow size distribution. The particle size and crystallinity were dependent on the synthesis conditions. However, the particle size distribution was not affected by the synthesis conditions. LiCoO₂ powders were used as cathode active material for lithium secondary battery and its charge/discharge property was investigated. The charge/discharge voltage of lithium secondary battery was 3.9V.

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The conductivity of sintered bodies in the ZrO₂-Y₂O₃-In₂O₃ system has been measured using the complex impedance method at 400-900°C in air. The conductivity of the sintered body with x=0.05 in (ZrO₂)_1-2x(Y₂O₃)x(In₂O₃)x (x=0.04-0.06) ceramics was the highest over the temperature range studied. In (ZrO₂)_0.90(Y₂O₃)_0.10-y(In₂O₃)y (y=0.02-0.08) ceramics, the conductivity increased with increasing In₂O₃ content, and decreased on annealing with increasing In₂O₃ content. In (ZrO₂)_0.92-z(Y₂O₃)_0.08(In₂O₃)z (z=0.02-0.07) ceramics, the conductivity slightly decreased with increasing In₂O₃ content and remained unchanged on annealing regardless of In₂O₃ content. It is presumed that the conduction mechanism is dominated by oxygen ion conduction in air.

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Application of the alumina powder composite sol-gel method to repairing of a damaged-part of glass lining was studied. The physico-chemical proerties of the composite gel-glass were evaluated. The feasibility of the alumina powder composite gel-glass was shown by the standard tests for permeation, adhesion strength, thermal fatigue strength and thermal shock strength, and that the durability against organic solvents was equivalent to that of the lining glass. The durability for water, acid or alkali aq, solution was less than those of the lining glass. It was proved that the composite gel-glass can be used for a six month period at least. The characteristic aspects of the alumina powder composite sol-gel method to be applied to repairing process includes (1) accelerated gelation, (2) small shrinkage on heating and (3) low working temperature at 300°C.

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Frost susceptibility of cement boards being reinforced with fibers (FRCB) was discussed from the view point of a three dimensional connecting structure of pores. It was found that the complexity in an interconnection of pores, indicating the degree of a spacial branching of pores, has decisive effects on the frost susceptibility of the FRCB materials, likewise as in the case of the fired clay roofing tiles and the fired bricks. Such higher complexity in the three dimensional pores branching structure brings much amount of unfrozen water which is entrapped in the pores structure during cooling. Resultantly, the hydraulic pressure due to freezing of the entrapped water causes a structural damage of the materials. It was found that the water absorption correlates strongly with the frost damage on the FRCB materials, in despite of rather poor correlation on the materials of fired clay roofing tiles and the bricks.

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Spherical porous silica glasses whose average diameter is 40μm are synthesized by the sol-gel process in W/O emulsions and a successive thermal treatment. The interconnected pore structure was seen in the particles. The pore size can be controlled by changing temperature of thermal treatment. The presence of residual carbons can be avoided by decreasing unreacted alkoxides with increasing water content of the initial solution in the sol-gel process.

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Eight kinds of RE-α-sialon (RE=Nd, Sm, Gd, Dy, Y, Ho, Er, Yb) were prepared by the sintering Si₃N₄, AlN and RE₂O₃ mixtures in a composition of RE_0.5(Si, Al)₁₂(O, N)₁₆ in nitrogen, and characterized by X-ray diffraction (XRD) analysis. The lattice constants, a and c, of Nd- to Dy-α-sialons were almost constant. When ionic radius was smaller than that of Dy³⁺, lattice constants increased with decreasing ionic radius of RE³⁺. The oxidation behavior of powders prepared by pulverizing these sialons was also examined in an air stream by differential thermal analysis (DTA) and XRD techniques. The DTA curves of these powders exhibited one or two exothermic peaks associated with the oxidation reaction in the range of 1200 and 1400°C. These peaks of Gd-, Dy-, Y-, Ho-, Er- and Yb-α-sialons shifted upwards with decreasing ionic radius of RE³⁺. The oxidation products formed by heating each sialon powder up to 1400°C were identified as α-cristobalite, RE₂Si₂O₇ and Al₂SiO₅. Among these products, the amount of RE₂Si₂O₇ in Er- and Yb-α-sialons was larger than that in other sialons. The amount of α-cristobalite was the smallest in the Yb-α-sialon.

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Packing of monosized spheres in cylinders is examined as a function of particle/cylinder size ratio. For size ratios ranging from 1/25 to 3/4, the packing efficiency of particles inside cylinder was found to decrease linearly with the size ratio. Using geometric analysis, the amount of extra pore volume in the packed particle structure was found to depend linearly on the surface area of the cylinder as well as the size of the particle.

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Discoloration in sintered alumina ceramics from colorless to brownish yellow by ultraviolet radiation was found and its mechanism was examined. UV-induced optical absorption bands were observed around 330 and 480nm. An intense red luminescence peak appeared around 650-690nm upon exciting UV region, and intensity of the luminescence band decreased with duration of UV-illumination time. ESR hyperfine structures of a ⁵⁵Mn²⁺ appearing in the spectrum of the specimen before illumination disappeared after UV-illumination. It is concluded that the discoloration is attributed to photochemical conversion of Mn²⁺ to Mn³⁺ by the following reaction: Mn²⁺+Fe³⁺=Mn³⁺+Fe²⁺. Here, Mn and Fe are contained in the specimen as trace impurities (in Referceram concentrations of Mn and Fe are 3ppm and 80ppm, respectively). Extinction coefficients of visible bands in Mn³⁺ are larger by 2 to 3 orders of magnitude than those of Mn²⁺. Therefore, the key species of the solarization of alumina is considered to be trace impurity of Mn²⁺.

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Highly dense ceramics of Ba₂YCu₄O₈ (Y-124) superconductor were successfully prepared under ordinary pressure of oxygen by the two-stage sintering, the compacted disks of precedently prepared Y-124 powders were sintered at 930°C for 2h, thereafter annealed at 800°C for 200h. The ceramics thus prepared have relative densities around 95%. It was also confirmed that the Y-124 phase of starting powders was decomposed to Ba₂YCu₃O_7-δ (Y-123) and CuO at 930°C, and then restored in the annealing at 800°C. Liquid-phase sintering may bring about the densification, since partial melt reportedly occurs at 930°C under oxygen pressure of 1013.25 hPa.

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