The general equation which represents the degree of the sintering under varying temperature not only for viscous flow but also for diffusion or evaporation-condensation mechanism has been derived as follows:
M/C=a^m+1e^-β/α[{aΣb_i/m+2+(1-aΣb_i/m+2)χ(x)}e^-(x-β)/(x-β)^m+2]_x1^x2 χ(x)=1-m+2/(x-β)+(m+2)(m+3)/(x-β)²-……} where, M: quantity of sintering, C: constant, α: rate of heating or cooling, a: activation energy term, b_i: temperature coefficient of each factor, m: power of absolute temperature in T^m, β: temperature coefficient of change in activation energy term, x: variable concerned both with time and temperature. The above equation is shown to be of a generalized form of various conventional sintering kinetic equations under varying temperature if corresponding value of m and other factors in the equation are given.

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Thermal decomposition of barium titanium (IV) bis (oxalate) oxide and the formation of barium titanate have been studied by means of TG, DTA, XRD, GC and IR. The result shows that the formation of BaTiO₃ from oxalate is described as follows: BaTiO(C₂O₄)₂⋅4H₂O→BaTiO(C₂O₄)₂→BaCO₃+TiO₂→BaTiO₃. It is supposed that TiO₂ produced in the process of the decomposition is amorphous and BaCO₃ transforms from an amorphous form to an orthorhombic form via a strained cubic form as temperature increases. The formation of BaTiO₃ is supposed to take place at a temperature above 720°C by the reaction between BaCO₃ (amorphous, strained cubic or orthorhombic) and amorphous TiO₂. The activation energy for the formation of BaTiO₃ has been calculated to be 46kcal/mol and it is much lower than that of the conventional process (58kcal/mol). The rate-determining step of the formation of BaTiO₃ from oxalate is decomposition process of BaCO₃, whereas that of the conventional process is diffusion.

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The glass-forming regions in the SiO₂-Li₂O system have been determined by cooling the melts containing 35-81mol% SiO₂ from liquidus temperature to room temperature at cooling rates; Q₁=4×10^-2, Q₂=1.4×10^-1, Q₃=4×10^-1, Q₄=3, Q₅=19, Q₆=4.4×10² and Q₇≅10⁵K/s. In the composition range SiO₂=35-75mol%, the glass-forming region expanded with increasing cooling rate, and the critical cooling rate Q* decreased with increasing silica content, and reached a minimum at SiO₂=75mol%. Phase separation was observed in the composition range SiO₂>70mol% at cooling rates Q₂-Q₅. However, the region in which the phase separation takes place decreased with increasing cooling rate, yet persisting in high silica compositions. A linear dependence was found in the log-log plot of liquidus viscosity η_L against Q*. When the logQ*-logη_L diagrams are compared with the system B₂O₃-Li₂O, the system SiO₂-Li₂O system was found to have a higher liquidus viscosity than B₂O₃-Li₂O system for a given critical cooling rate. The difference in the glass-forming ability between the two systems was analyzed in terms of kinetic parameters based on the crystallization formula, and the poor glass-forming ability in the system SiO₂-Li₂O in comparison with B₂O₃-Li₂O system was elucidated to be due to a smaller fusion entropy in the former. This implies a smaller structural difference upon crystallization of the silicate in comparison with that of the borate.

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The third component (CaO, SrO, BaO, SiO₂, CoO and MnO) was added to ZnO ceramics containing 1mol% Nb₂O₅ in order to alter the property of melts formed during firing, and the electrical resistivity, V-I relation and microstructure of sintered bodies were examined. The addition of CaO, SrO and BaO improved the wetting of intergranular layers to ZnO grains and increased the room-temperature electrical resistivity. The addition of SiO₂ also improved the wetting, but did not affect the electrical property. CoO gave no changes to the fired body. Although it did not strongly affect the microstructure, the addition of MnO markedly increased the room-temperature resistivity and gave rise to nonlinear V-I relation. The ZnO specimen containing only MnO also showed high electrical resistivity and some nonlinear V-I relation. The addition of a small amount of Nb₂O₅ to ZnO-MnO system strikingly decreased the electrical resistivity, but an increase in the amount of Nb₂O₅ addition (1mol%) enhanced again the electrical resistivity and led to a nonlinear V-I characteristic.

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In the delafossite (CuFeO₂) type compounds (A⁺B³⁺O₂), structural variation with B-site ion was studied. The deformation of BO₆ octahedron in the direction of the three-fold axis increased with increasing ionic radius of the B-site ion, r_B. The degree of deformation increased drastically at r_B greater than 0.8-0.9Å. These results were analyzed through the computation of lattice energy. The crystal was assumed basically ionic and the covalency of the A-O-B bonds in the crystal was taken into account.

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ZrN powder was prepared from ZrCl₄ by the halogenide process in a nitrogen gas flow (100-200ml/min) at the temperatures from 200°C to 1050°C. Particularly, the influences of reducing agents, Al, Mg and Zn powder were examined. The Al powder was found to be the most effective reducing agent among them, and ZrN powder was odtained above 800°C. In the slow nitriding reaction, however, an alloy phase of Al₃Zr was formed. The apparent activation energy of the reaction was 28.7kcal/mol (850°-1050°C). The fine powder (0.1-0.3μm) of one-phase ZrN was obtained at 1050°C after 1h. The lattice parameter a and the crystallite size of ZrN were 4.575Å and 259Å, respectively. However, because of the sublimation loss of ZrCl₄, the residual Al was found in the products. This Al was removed almost completely by washing with 1N NaOH. On the other hand, in the system ZrCl₄-Mg-N₂, the process of the nitriding reaction was slow, and only coarse particles of ZrN were obtained. In the system ZrCl₄-Zn-N₂, ZrN was not prepared.

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The three point flexural strength of β-sialons hot-pressed at 1800°C under a pressure of 200kg/cm² for 1h was measured at room temperature and at 1400°C. The compositions of starting mixtures prepared from α-Si₃N₄, α-Al₂O₃ and AlN were Z=1 (1.8), Z=1 (2.8), Z=1 (4) and Z=1 (5.5), the number in parenthesis shows the deviation from that of Z=1 composition in equivalent oxygen %. Following results were obtained:
1) β-sialons with Z=1 (1.8) and Z=1 (2.8) were incomplete in densification. β-sialons with Z=1 (4) and Z=1 (5.5) showed complete densification.
2) All samples consisted of β-sialon as crystalline phase, but a glassy phase was detected in grain boundaries by SEM observation.
3) The flexural strength of β-sialons with Z=1 (4) was 55.5kg/mm² and that of β-sialon with Z=1 (1.8), Z=1 (2.8) and Z=1 (5.5) was 22.7, 36.7 and 33.0kg/mm², respectively at room temperature. The flexural strength of those samples showed no degradation at 1400°C.
4) The flexural strength was originated from interior defects such as void, poorly sintered part and cluster of large grains, for which the heterogeneity of starting mixture is responsible. The fracture propagated transgranularly in all samples both at room temperature and at 1400°C.

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A large amount of thermal energy is required for the firing of porcelain wares which is generally carried out at a temperature as high as 1300°C. In order to minimize energy required in the firing of porcelain, we developed a new composition which could be fired at a lower temperature of 1100°C without losing its porcelain properties, and its characteristics such as the vitrification behavior were investigated. The composition of the body was expressed as 0.40KNaO⋅0.16CaO⋅0.21MgO⋅1.00Al₂O₃⋅6.99SiO₂⋅0.10B₂O₃ by the Seger formula. Although the body contained B₂O₃-frit, alkali and alkaline earth metals as additives, a stable vitrification process of the body was maintained, and no difference could be observed in the mineral composition and physical characteristics of the porcelain prepared from the body and the typical vitrified porcelains prepared by the conventional method. This green body is based upon pottery stone (Toseki) which possesses plasticity, therefore, no modification of the conventional process is necessary in molding the body. An experiment carried out using an experimental kiln (internal volume of about 0.5m³) showed that reductions in the firing time of about 30% and in the fuel consumption of 30-40% are obtained as compared with the firing of a body containing no additive.

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