The system CePO4–K3PO4

The phase diagram of the system CePO4–K3PO4 has been determined based on investigations by differential thermal analysis, X-ray powder diffraction, IR spectroscopy and optical microscopy. The system contains only one intermediate compound K3Ce(PO4)2, which melts incongruently at (1500±20)°C. This compound is stable down to room temperature and exhibits a polymorphic transition at 1180°C. It was confirmed that the low-temperature form β-K3Ce(PO4)2 crystallizes in a monoclinic system, space group P21/m with unit cell parameters a=9.579 (5), b=5.634 (6), c=7.468 (5) Å; α=γ=90°, β=90.81 (3)°; V=403.083 Å3.