Phase equilibria in the ErPO4–KPO3–Er(PO3)3 partial system

Phase equilibria in the ErPO4–KPO3–Er(PO3)3 partial system were established, and the primary crystallization fields of the phosphates occurring in the composition range of ErPO4, KErP2O7, KPO3, Er(PO3)3, KEr(PO3)4 were defined. Two polythermal binary cross-sections, KErP2O7–Er(PO3)3 and KErP2O7–KEr(PO3)4, which are quasi-binary only in the subsolidus region (i.e. below 855 °C and 640 °C, respectively), were determined, and their phase diagrams were elaborated. Three invariant points, two ternary peritectics P1 (855 °C) and P2 (640 °C) as well as one ternary eutectic E (530 °C) were found in the ErPO4–KPO3–Er(PO3)3 system. Alloy crystallization ends with the solidification of the ternary eutectic (KErP2O7 + KEr(PO3)4 + KPO3). The studies were carried out by thermoanalytical methods (DSC/TG) and powder X-ray diffraction analysis (PXRD).