The metastability of α-CaSO₄·1/2H₂O in 2.62-14.83% H₂SO₄ solutions was studied by wet DTA method. On the basis of the measured values of reaction temperature and induction period for hydration of a-CaSO₄·1/2H₂O in 2.62-14.83% H₂SO₄ solutions in this study and previous results^{1) -3)} , the relation between H₂SO₄ concentration Z (%) and reaction temperature Y (°C) in the case of 1 minute induction period was given as follows : Y= _38.75e^-0.1344z+ 86.74 (where Z= 2.62-14.83) As a result of estimating the maximum point from above and previous similar relation in 20.20-40.48% H₂SO₄ solutions³⁾ , the value of Z= 17.29% and Y= 82.94°C was obtained. The metastable zone for α-CaSO₄·1/2H₂O in 2.62-40.48% H₂SO₄ solutions was determined. The phase diagram for metastably of calcium sulfate in the CaSO₄-H₂SO₄-H₂O system was shown by the isochrones in the case of 1 minute induction period for dehydration of CaSO₄.2H₂O²⁾ and hydration of CaSO₄·1/2H₂O in this and previous³⁾ studies.

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Sintered body of PbZrO₃-PbTiO₃-Pb (Zn_1/3Nb_2/3) O₃ system with high pyroelectric coefficient over a wide temperature range was obtained. Sintered body of a mixture of three compositions having pyroelectric peaks at different temperatures exhibited single pyroelectric peak. This was caused from the diffusion during the sintering. To avoid the effect of the diffusion, granules with different compositions were mixed, pressed into a powder compact and sintered. The compositional change by diffusion was suppressed by this method. This technique enabled the combination of different pyroelectric properties.

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The new process to produce calcium ferrite system, calcium aluminate system and calcium alumino ferrite system fluxes for steel making were examined. These fluxes were obtained by calcination of Fe₂O₃ -coating, Al₂O₃ -coating and Fe₂O₃-Al₂O₃ mixture coating limestone. The products were characterized by means of X-ray diffraction, scanning electron microscope and energy-dispersion X-ray spectrometry.
As a result of experiment, calcium ferrite (2CaO·Fe₂O₃), calcium aluminate (3CaO·Al₂O₃ and 12CaO·7Al₂O₃) and calcium alumino ferrite (4CaO·Al₂O₃·Fe₂O₃) could be synthesized same time with calcium oxide. Besides, fluxes were stuck on or penetrated into calcium oxide. Calcium alumino ferrite system flux was particularly penetrated to insides of calcium oxide. Formation of Fe-rich C₄AF or C₄AF-C₂F solid solution were important to promote its penetration.

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