Study of phase relationships in the Sr3(PO4)2–CePO4 system. Phase diagram and thermal characteristics of phases

Abstract

A diagram representing phase relationships in the Sr3(PO4)2–CePO4 phosphate system has been developed on the basis of results obtained by thermal analysis (DTA/DSC/TGA) and X-ray diffraction (XRD) methods. One intermediate compound with the formula Sr3Ce(PO4)3 occurs in the Sr3(PO4)2–CePO4 system at temperatures exceeding 1045 °C. The compound has a eulytite structure with the following structural parameters: a=b=c=10.1655(8) Å, α=β=γ=90.00°, V=1050.46(6) Å3. It's melting point exceeds 1950 °C. A limited solid solution exists in the system, which possesses the structure of a low-temperature form of Sr3(PO4)2. At 1000 °C the maximal concentration of CePO4 in the solid solution is below 20 mol%. The solid solution phase field narrows with increased temperature. There is a eutectic point in the {Sr3(PO4)2+Sr3Ce(PO4)3} phase field at 1765 °C and 15 mol% of CePO4. The melting temperature of Sr3(PO4)2 is 1882±15 °C.