Sintering of polycrystalline bodies consisting of eucryptite (Li₂O⋅Al₂O₃⋅2SiO₂), spodumene (Li₂O⋅Al₂O₃⋅4SiO₂), and cordierite (2MgO⋅2Al₂O₃⋅5SiO₂) which have low coefficient of thermal expansion was investigated. From the solid phase reaction of the binary system between eucryptite and cordierite at 1000-1400°C, it was assumed that homogeneous β-eucryptite solid solution was formed up to 30wt% of cordierite composition at 1300°C.
After precalcining of the mixtures (compositional range of 0-40wt% cordierite) to form the intended crystalline phase, powder compacts were sintered with addition of MgF₂ at various temperatures. Perfect-mixing technique, one of the additional forms of MgF₂ used in this experiment, was the best procedure to obtain the high-density bodies.
With the addition of MgF₂, densification occurred in the initial few minutes followed by the decrease in the density with increasing of sintering time. The fast early shrinkage may be caused by formation of liquid phase and spinel. The density decrease was particularly remarkable in the case of 10 and 20wt% cordierite composition, and it was considered that this phenomenon resulted from the resolution of spinet, which was formed in the initial stage of the sintering, into β-eucryptite solid solution.
Polycrystalline bodies of eucryptite-20wt% cordierite sintered at 1300°C with the addition of 1wt% MgF₂ had 93% of theoretical density and -20×10^-7 deg^-1 of thermal expansion coefficient in the range of room temperature to 800°C.

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The gas pressure sintering of silicon nitride with 5% MgO as an additive was performed under 10 atm N₂ at 1450-1900°C. Maximum density of 95% of theoretical value, 3.19g/cm³, was obtained at 1800°C. The densification was due to liquid phase sintering and divided into two processes, rearrangement and solution-precipitation.
Microstructural studies of cleavages and etched ones revealed that the densification was mainly attributed to rearrangement at lower temperatures than 1500°C and solution-precipitation at higher temperatures.
The composition of the grain boundary phase of Si₃N₄ sintered at 1700°C was investigated by Auger Electron Spectroscopy (AES). The result suggested that the grain boundary phase in this system was CaO-MgO-SiO₂. The shrinkage at 1500°C, i.e. lower temperature than melting point of enstatite (MgSiO₃, 1557°C), was attributed to CaO which extremely lowered the melting point of the grain boundary phase compared to MgO-SiO₂ system.

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This study was concerned with the formation and color development of the spinel solid solution in CoO-MgO-Al₂O₃-Cr₂O₃-SnO₂ system, and its application to colored glazes.
Specimens were prepared by calcining the oxide and hydroxide mixtures at 1450°C for 1 h. The formation of spinel solid solution was examined by X-ray diffraction, the color was discussed by measuring the spectral reflectance, and the stability of the spinel in glazes was tested.
The results were summarized as follows.
1) Except a few systems, a continuous solid solution was confirmed by X-ray analysis.
2) As the amount of Cr³⁺ increased in MgO-Cr₂O₃-SnO₂ system, the color changed from white through grayish yellow to yellowish gray, and the absorption of Cr³⁺ shifted towards short wavelength region.
3) An increase Al³⁺ in MgO-Al₂O₃-Cr₂O₃ system, caused the color to change from yellowish gray through purplish pink to white, and the absorption of Cr³⁺ shifted towards short wavelength region.
4) The colors obtained in MgO-Al₂O₃-Cr₂O₃-SnO₂ system, ranged from white through grayish yellow and beige to purplish pink.
5) An increase of Cr³⁺ in CoO-MgO-Cr₂O₃-SnO₂ system, yielded the colors ranging from bright greenish blue through light blue to turquoise, and the absorption of Cr³⁺ shifted towards short wavelength region.
6) As the amount of Al³⁺ increased in CoO-MgO-Al₂O₃-Cr₂O₃ system, the colors ranging from turquoise through strong greenish blue to bright blue developed, and the absorptions of Co²⁺ and Cr³⁺ shifted towards short wavelength region.
7) As the amount of Al³⁺ increased in CoO-MgO-Al₂O₃-SnO₂ system, the color changed from bright greenish blue to bright blue, and the absorption of Co²⁺ shifted towards short wavelength region.
8) The colors ranging from bright blue through greenish blue to turquoise developed in CoO-MgO-Al₂O₃-Cr₂O₃-SnO₂ system.
9) According to the results of the colored glaze test, specimens with the composition of Cr³⁺ rich region were stable as a glaze stain. CoO-MgO-Al₂O₃-Cr₂O₃-SnO₂ system revealed the brilliant hue similar to peacock in lime glaze, and clean greenish blue in magnesia-lime glaze.

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Investigating the resistivity against frost action on an earthenware body under one dimensional-cooling in connection with particle orientation, cooling direction and cooling rate, some conclusions have been obtained as follows:
(1) Regardless of the cooling direction, the repetition of freezing and thawing cycle causes stratified cracks along the direction of particle orientation (parallel to (00l) planes of platy clay particles), the direction of the weakest bonding strength. Under the absence of particle orientation cracks are preferably developed perpendicularly to the cooling direction.
(2) The resistivity against frost action is closely related to the rate of cooling and the cooling direction. When the cooling direction is parallel (perpendicular) to the direction of particle orientation, the greater (the smaller) is the cooling rate the more severe damages are caused. The phenomenon is derived from the easiness of leaving small quantity of water temporarily unfrozen inside capillaries during freezing.

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The effect of porosity on the rate of dissolution of polycrystalline zircon specimens in molten iron oxide was studied by rotating cylindrical zircon specimens at a speed of 100rpm in a stationary crucible containing the melt at 1500°C. Zircon specimens were about 20mm in diameter and 30mm in length. The apparent porosity was from about 4 to 30 percent. Then, the effect of quantity of dissolved zircon into molten iron oxide on the dissolution rate of specimen with 15.5 percent apparent porosity was studied under the condition of 100rpm at 1500°C. The dissolution rate was calculated from the change in radius of the specimens. The relation between the rate of dissolution and the porosity of specimens was not given to direct proportion but the former was accelerated as the latter increase. Extrapolating from above relation, the dissolution rate was about 4.8×10^-3cm/sec in the case of non-porosity specimen.
On the other hand, the penetration of molten iron oxide into specimens depended markedly on its porosity, its penetration was able to be prevented by specimens below at least 15.5 percent porosity. Then, the dissolution rate of zircon specimen in the melt was remarkably affected by the quantity of dissolved zircon into molten iron oxide, and the dissolution rate was reduced below half of it into molten iron oxide, even if the quantity of dissolved zircon was 5 percent. The relation between the dissolution rate (Vcm/sec) and the quantity of dissolved zircon into molten iron oxide (Z, 100wt%=1) was given to next formula.
logV=-6.65Z-2.12

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Cylindrical dumet (copper-clad Fe-Ni alloy wire)-to-glass seals were formed using two kinds of alkali lead (20 and 28wt% PbO) silicate glasses. Concentration distribution of elements along radial direction was observed by EPMA method. The results were as follows:
1) Copper oxide on dumet surfaces diffused into glasses. Diffusion fronts were 20-60μ distant from dumet-glass interfaces depending on sealing operation and PbO content of glasses.
2) Sodium and potassium showed flat distribution in glass except high concentration at the interfaces.
3) Lead showed peculiar distribution. Maximum and minimum concentration points were formed at 3-8μ and 6-21μ distance from the interfaces, respectively. The distance increased with increasing diffusion distance of copper.
4) Dumet wire preheated to form thick copper oxide layer on the surfaces carried intermediate layer 7μ thick after sealing at the interface. The layer was vacuum-tight.
5) Copper oxide on copper (Cu₂O monomolecular layer in the extreme case) seemed to behave as bridging layer between copper and copper-containing glass.
6) Rearrangement of elements durings sealing operation seemed to improve glass-metal adhesion.

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A structure model for K₂O⋅2WO₃ glass has been selected and proposed out of many possible models on the basis of the radial distribution curve calculated from the X-ray diffraction pattern. The adequacy of each model was judged primarily from the agreement of the radial distribution curve calculated for the model as a sum of the pair functions to the curve obtained experimentally. It was nearly impossible, however, to calculate a radial distribution curve for every possible model, so the adequacy of each model was evaluated beforehand on the basis of some criteria including Pauling's rule of parsimony. After screening of models, three models A, B, C remained in which each structure unit consisted of a WO₄ tetrahedron and a WO₆ octahedron combined with two K⁺ ions. The model A has a layer-structure and the model B and C have chain-like one (Fig. 4). Since W-W atomic pairs strongly affected the radial distribution curve, several structural parameters were changed in order to know how W-W distances varied (Fig. 6, 9, 12). For the two models other than the chain-like model B, W-W distances did not correspond well to those in the experimental radial distribution curve. Two structures, B_S and B_AS, having the different sites of tetrahedra with respect to an octahedron were possible for the model B (Fig. 1 (a), 8). The W-W distances for the model B_S with the particular combination of the structural parameters (P in Fig. 9) showed good correspondency to those in the experimental radial distribution curve. After the introduction of disorder based on statistical distribution and structure flexibility, the curve calculated for the model B_S resulted in good agreement with the experimental one (Fig. 11). The model B_AS was also found to be acceptable. In conclusion, the layer-structure model A with the 6-membered rings of W-atoms, which seemed to be more suitable for glass structure, was concluded to be inadequate, and the 3-membered rings of W-atoms similar to those found in the crystalline structure were suggested to exist in the glass.

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The Cu⁺-Cu²⁺ oxidation-reduction equilibria in binary alkali silicate glasses were studied by melting the glasses in platinum crucibles in air with 0.5mol% CuO and by making chemical analysis and measurement of optical absorption. The equilibrium concentration ratio [Cu²⁺]/[Cu⁺] in 30Na₂O⋅70SiO₂ melt decreased with the rise in temperature, as expected from the known behavior of oxidized-reduced ion pairs of many other multivalent elements. The ratio [Cu²⁺]/[Cu⁺] in 30R₂O⋅70SiO₂ melts (R=Li, Na, K, Cs) at a given temperature decreased in the order Li₂O>Na₂O>K₂O>Cs₂O, that is, with the increase in basicity of the melt, in contrary to the expectation derived from the previous results on the equilibria of many other multivalent ions. The intensity of the optical absorption at the wavelength of 800nm served in indicating the amount of Cu²⁺ ions in glasses and its measurement gave the similar information on the oxidation-reduction equilibria of copper ions in melts to the chemical analysis.

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The compositional range of the glass formation in the system RO(R₂O)-TiO₂-P₂O₅(R=K, Ca, Be) and electrical resistivity of the glasses were studied.
The results are summarized as follows;
1) The compositional range of the glass formation obtained by the quenching method was similar to each other in three systems (R=K, Ca, Be).
In glasses, maximum contents of TiO₂ were 65mol%.
2) In the 10K₂O⋅50TiO₂⋅40P₂O₅ composition glass, the precipitated crystal by heat treatment at 800°C were TiO₂ (anatase) and unknown crystal (K₂O⋅TiO₂⋅P₂O₅ system).
3) The temperature dependence of resistivity for the phosphate glasses containing Ti³⁺ was given by
ρ=ρ₀ exp(ΔE/kT)
in which ρ is resistivity, ρ₀, constant, ΔE, activation energy, T, absolute temperature, and k, Boltzman's constant. But the linear relationship between log ρ and 1/T bent into two straight line in all glasses in the neighborhood of 100°C. In the xK₂O-(60-x) TiO₂-40P₂O₅ system, the resistivity of the glasses decreased with increasing TiO₂ contents. Addition of Ti³⁺ ion to the base glass (10K₂O⋅50TiO₂⋅40P₂O₅) decreased electrical resistivity very much, and also decreased the apparent activation energies for electrical conduction.
4) The electrical resistivity of crystallized glasses decreased with increasing the quantity of crystal deposited in the glasses and the concentration of Ti³⁺ ion. It was assumed that the decreases of resistivity by crystallization were due to the deposition of nonstoichiometric crystals having higher electrical conductivities.
5) The Seebeck coefficient was nearly independent on temperature in the range of 40 to 150°C and it's values were -0.36mV/°C.
6) By addition of a small amounts of FeO or V₂O₃ to base glass, electrical resistivities were decreased about one order of magnitude.

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