Ultramarines were synthesized from Linde A molecular sieves (MS5A, MS4A) via the following procedures: (1) impregnation of MS with Na₂S in the saturated aqueous solution of Na₂S and drying the resulting MS-Na₂S, (2) adsorption of sulfur vapor on the MS-Na₂S at 500°C, (3) heating of the MS-Na₂S-S (500°C) up to about 820°C, and (4) air oxidation of MS-Na₂S-S (820°C) at 500°C and above. In order to elucidate the chemical roles of Na₂S, S and H₂O in the procedures above, structural and mechanistic investigations were carried out. X-ray diffraction patterns of MS-Na₂S-S (500°C) showed the change to that of ultramarine on increasing the temperature from 700°C to 820°C (17°C/min). Heat treatments of both MS4A and MS4A-Na₂S up to 820°C led to the formation of carnegieite. Abovementioned facts indicate that Na₂S_x in the α-cage was pressed into the β-cage at about 700°C and the presence of Na₂S_x in the β-cage provided protection against the collapse of β-cage. The migration of Na₂S_x through the opening of the β-cage at about 700°C was ascertained by the fact that the decomposition of SO₂ which easily occurs if SO₂ and Na₂S_x coexist started at 700°C on MS-Na₂S-S (820°C). In the oxidation of the ultramarine, molecular oxygen was less active than the oxides of sulfur formed in the air oxidation process. Because the oxides of sulfur are almost unable to pass through the narrow opening of the β-cage, it is reasonable to assume that the oxidation was mainly caused by atomic oxygen radicals or ·OH radical produced from the oxides of sulfur. ESR signals attributable to ·O₂H radical were observed in the ultramarines which were obtained from MS-Na₂S-S (820°C) by the air oxidation at 500°C. This fact indicates the presence of ·OH radical in the air oxidation process. Heating the mixture of MS4A-Na₂S-S (820°C, S: 5wt%, yellow), sulfur and H₂O up to 800°C in the N₂ stream resulted in the evolution of H₂S and blue coloration of ultramarine. In this case, sulfur content of the ultramarine did not change. Since the evolution of H₂S must accompany the formation of oxidants from H₂O, these facts show that H₂O acts as an oxidizing agent on ultramarine at high temperature under the presence of sulfur.

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Thermal displacement reaction proceeds to give stable phase pair consisted of the larger cation couple to the larger anion and vice versa, but the chemical composition of the product differs with the combination of the reaction pair. Follwing the previous paper concerning the reaction SrSO₄+BaCO₃, the reaction process was studied from the standpoint of the difference of cation radius of alkaline earth compounds. Three solid-solid reaction systems, CaSO₄+SrCO₃, CaSO₄+BaCO₃ and CaSO₄+(Sr, Ba)CO₃, were examined by X-ray diffraction, thermal analysis (DTA) and ion chromatographic analysis. The reaction pairs, CaCO₃+SrSO₄ and CaCO₃+BaSO₄, were also used to examine the mutual miscibility between the reactants. Phase observed during the course of the reaction were consisted of a partial solid solution of the reciprocal products for CaSO₄+SrCO₃, whereas the reaction proceeded by a simple exchange mode for CaSO₄+BaCO₃. BaCO₃ with larger cation radius was more reactive than SrCO₃ against CaSO₄, the fact of which suggested the driving force would be the difference of the cations radii to be exchanged in such case of sulfate and carbonate reaction couple.

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Structural changes on thermal phase transition have been investigated by X-ray diffraction technique on a piezoelectric crystal BaZnGeO₄. Space groups and cell dimensions are: P6₃22, a=5.407 (2) Å and c=8.975 (5) Å (at 900°C) for phase I, and P6₃, a=9.320 (1) Å and c=8.866 (5) Å (at 420°C) for phase II. The lattice vectors of phase I and phase II are in the relations, a_I=(2a_II+b_II)/3, b_I=(b_II-a_II)/3 and c_I=c_II. The change in intensities of superlattice reflections with temperature indicates an abrupt change of the structure at the phase transition point between the two phases. At 420°C, 710°C, 800°C and 900°C, the crystal structures were refined with single-crystal X-ray diffraction data to the final R values of 0.076, 0.062, 0.052 and 0.061 for 575, 417, 138 and 132 observed reflections, respectively. The crystal has a stuffed structure derived from the high tridymite frame-work with Ba²⁺ ions at the large interstices between the six-membered rings of ZnO₄ and GeO₄ tetrahedra. Bond distances suggested ordering of Ge⁴⁺ and Zn²⁺ ions among the tetrahedral sites in the structure of phase II as in the structure of phase III, whereas these cations were revealed to occupy the tetrahedral sites in the completely disordered way in phase I.

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An equation has been derived which gives the fraction X(0) of crystallized phase in a continuously cooling melt assuming homogeneous nucleation and isotropic crystal growth. From this equation a tentative and simple expression for X(0) has been constructed in terms of liquid parameters which enables one to understand the essential roles of liquid parameters involved in the glass formation of a supercooled liquid. Assuming a minimal constant value for X(0) one can estimate the critical cooling rate Q of a given melt from the liquid parameters by,
logQ=-logη_L-0.06E_η/T_L-3T₀/T_L+2logT_L-logV-38α³ΔS_f-0.25logX(0)+5±0.5 (1)
where Q is critical cooling rate (K/s), η_L is liquidus viscosity (poise), E_η is activation energy for viscous flow (cal/mol) at liquidus temperature T_L(K), T₀ is a constant in the Fulcher type viscosity (K), V is molar volume (cm³/mol), ΔS_f is fusion entropy per flow unit (cal/K·mol) and α is dimensionless surface tension in the range 0.3-0.5.
Although E_q. (1) has been derived for one-component liquid, it may be valid also for multi-component liquid in a semi-quantitative way as has been tested in the B₂O₃-Na₂O system.

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Stoichiometric MgAl₂O₄ spinel powders have been synthesized from magnesium and aluminum nitrates solution by spray pyrolysis method. The obtained powders were characterized by means of X-ray diffraction, measurements of specific surface area, grain-size and pore-size distribution and scanning electron microscopy. The powders synthesized above 800°C consisted of spinel phase. The synthesized spinel powder consisted of agglomerated hollow spherical particles. The particle size of in the agglomerates ranged from submicron to 20μm in diameter. Further, each hollow spherical particle was formed by very fine primary particles (100 to 800Å in diameter) among which much smaller pores (10 to 100Å in diameter) were included. Diameter of the agglomerates increased as the concentration of the solution and/or the water content in the solvent was increased. The specific surface area and the pore volume of the powders depended on the ratio of water/methanol content in the solvent, but they were not affected by solution concentration. The specific surface area and the pore volume of the powders increased with decreasing water/methanol ratio. When the water/methanol ratio was decreased, the aggelomerates became fragile and tend to fracture more easily by powder compaction. The effect of water/methanol ratio on the configuration of the powders was considered as follows. As the methanol content in the solvent is increased, the vaporization rate of the whole solvent is accelerated and the degree of supersaturation in the sprayed droplet is increased. Consequently, number of nuclei of precipitation in the droplet may be increased, and results in the smaller primary particles. As the 0.3M W50 solution was sprayed at 800°C, fine grained and porous spinel powders with a specific surface area of 109m²/g was obtained.

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Density, elastic moduli, Vickers hardness and thermal expansion coefficient for some metaphosphate glasses have been studied. Two linear relationships existed between mean molar volume and the cube of radii of modifier cation in glasses (rM2+3 for Ca, Sr, Ba, Mg and Zn, and 3rM+3 for Li and Na). One corresponds to normal type glasses (Ca, Sr, Ba, Li and Na groups) and the other corresponds to anomalous type glasses (Mg and Zn groups) proposed by Kordes. It is estimated that anomalous type glasses have more vacant space than normal ones by comparison of these linear lines. There were constant relationships between elastic moduli (bulk modulus K, Young's modulus E, shear modulus G and Poisson's ratio ν) and mean atomic volume V as follows; K=k1Vf, E=k2Vg, G=k3Vh, 1+ν=k4Vj, where f=-1.1, g=-2.9, h=-3.2 and j=0.310 for Ca, Sr, and Ba groups, f=-1.6, g=-2.3, h=-2.4 and j=0.118 for Li and Na groups, and f=-7.4, g=-7.3, h=-7.3 and j=-0.026 for Mg and Zn groups. Two linear relationships existed between Vickers hardness and cation-oxygen attraction (2Z/d2). One corresponds to normal type glasses and the other corresponds to anomalous type glasses, where Zc is the number of positive charge on the cation and d is sum of the radii of cation and oxygen ion. The Vickers hardness of normal type glasses were larger than that of anomalous type glasses. Thermal expansion coefficients were proportional to reciprocal of cation-oxygen attraction (d2/2Z) regardless of different stucture between normal and anomalous type glasses.

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To improve mechanical strength of aluminum titanate ceramic, relations between microstructure and mechanical strength of the fired specimens were investigated. Specimens were prepared from stoichiometric mixtures of calcined aluminum hydroxide at 700°-1200°C. for 2h or fine corundum and anatase or rutile. During heating, alumina and titania of all specimens were converted into corundum and rutile, and aluminum titanate formation started from then at about 1300°C and completed at 1450°C.
The specimens were fired at 1350°C, 1400°C, 1450°C and 1500°C each for 4h. The density of any specimen was less than 80% of the theoretical density, and showed minimum for the specimens fired at 1400°C, which caused by volume expansion accompanied with formation of aluminum titanate from alumina and rutile. Size of aluminum titanate grains of fired bodies was 3-4μm. Many grains aggromerated each other and formed large aggregates of 100-200μm. Under the crossed nicols figure of polarization microscope, each aluminum titanate grain in one large aggregate showed simultaneous extinction, which means that the aluminum titanate grains in each aggregate oriented strongly. Around the aggregates-those were called as domains-large cracks often existed, which might be caused by large thermal expansion anisotropy of aluminum titanate. Thermally, one aggregate might behave as a single crystal. Size of the domains could be reduced by rapid heating or addition of small amount of synthesized aluminum titanate powder. Logarithmic plot of amount of synthesized aluminum titanate addition vs. domain size showed straight line with slope of about -1/3. Addition of only 0.025wt% aluminum titanate powder accelerated markedly formation of aluminum titanate at 1340°C for 10min. From these results it was inferred that reaction of formation of aluminum titanate from corundum and rutile was determined by nucleus formation mechanism, and that newly formed aluminum titanate grains oriented strongly with the same crystalline direction as initial grains and reaction rate of the aluminum titanate might be faster than growth rate of each grain, so the domain structure was formed. The cracks around the domains reduced strength of the fired specimens. Fired specimens with high density not always showed high strength, so size and amount of the cracks were more harmful factors than density to their mechanical strength. Decrease of domain size by rapid heating or addition of small amount of synthesized aluminum titanate powder decreased the crack size and increased strength of the fired specimens.

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