Phase equilibria in the YPO4-Rb3PO4 system

Abstract

The phase equilibria occurring in the YPO4-Rb3PO 4 system were investigated by thermoanalytical methods, X-ray powder diffraction, and ICP-OES. On the basis of the obtained results, its phase diagram is proposed. It was found that the system includes two intermediate compounds Rb3Y(PO4)2 and Rb3Y 2(PO4)3. The Rb3Y(PO 4)2 compound melts congruently at 1300 C. The Rb 3Y2(PO4)3 orthophosphate was previously unknown. This intermediate compound is high-temperature unstable and decomposes within the temperature range 1300-1330 C to YPO4 and Rb3Y(PO4)2. The decomposition process is irreversible. It was found that the Rb3Y2(PO 4)3 orthophosphate is isostructural with Rb 3Yb2(PO4)3 and crystallizes in the cubic system (a = 1.70226 nm). © 2012 The Author(s).