Al2O3-Pr2O3系の高温状態図

水野 正雄, 山田 豊章, 野口 哲男

doi:10.2109/jcersj1950.85.30

By the use of a heliostat type solar furnace, the liquidus curve of Al₂O₃-Pr₂O₃ system was measured. Temperature was measured with specular reflection method. The brightness temperature and spectral refractivity of the freezing point of the composition in the system was obtained by the brightness pyrometer at 0.65μm. The quenched specimens were examined by petrographic microscope, chemical analysis and X-ray diffraction; high-temperature diffraction was also employed. The single phase of PrAlO₃ of perovskite structure was obtained by heating the equimolar mixture of Al₂O₃ and Pr₂O₃ at 1600°C in an electric resistance furnace, and also by cooling the fused specimen in the solar furnace. A β-alumina type phase of Pr₂O₃⋅11Al₂O₃ was also observed. However, in the heated and fused specimen of Pr₂O₃⋅11Al₂O₃ composition, the β-alumina type phase was not observed as a single phase, but always accompanied by PrAlO₃ phase. The reversible phase transition. of PrAlO₃ between the rhombohedral and cubic form was also confirmed at about 950°C by high temperature X-ray diffractometry. The lattice parameters were a₀=5.358Å, α=60°11' for the rhombohedral and a₀=3.795Å for the cubic form and thus the variation of unit cell volume ΔV was only 0.24 percent. Colour of the PrAlO₃ phase was olive, and its refractive indices were γ=2.050±0.002, α=2.040±0.002. A tentative phase diagram for the Al₂O₃-Pr₂O₃ system at a high temperature was presented. The phase diagram shows two eutectics at 1800°C with 20.69mol percent Pr₂O₃, and at 1819°C with 75mol percent Pr₂O₃ composition. The cooling curve of Pr₂O₃ showed two exothermic peaks related to solid state phase transformations below the solidification point.

Al<sub>2</sub>O<sub>3</sub>-Pr<sub>2</sub>O<sub>3</sub>系の高温状態図

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