材料期刊网

The subsolidus phase relations in the BiO3/2-PrO11/6-CuO ternary oxide system and in the related binary systems as well as crystallographic parameters of selected phases are investigated by X-ray powder diffraction. The subsolidus phase relation at room temperature in the BiO3/2-PrO11/6-CuO system can be divided into three two-phase regions and five three-phase regions. No ternary compound was found. There exist two solid solutions (BiO3/2)(1-x)(PrO11/6)(x) in the BiO3/2-PrO11/6 system with x = 0.1-0.3 and x = 0.69-0.72, respectively. Both belong to the rhombohedral system (R(3) over barm$). The lattice parameters represented by a hexagonal cell are a = 3.9986(7) Angstrom, c = 27.459(6) Angstrom for Bi3PrOy (alpha phase) and a = 3.8729(5) Angstrom, c = 9.7452(2) Angstrom for Bi3Pr7Oy (gamma phase). The Rietveld refinement result of the crystal structure of Bi3Pr7Oy reveals that Bi/Pr atoms occupy statistically the 3a site and O atoms and vacancies occupy the 6c site. Pr3+ is the major state in the two solid solutions. (C) 1996 Academic Press, Inc.