Phase Relationships in the Tricalcium Phosphate-Cerium Phosphate System. Thermal behavior of Phases Present in the System

摘要

A diagram representing the phase relationships in the Ca_3(PO_4)_2-CePO_4 phosphate system has been developed on the basis of results obtained using thermal analysis (DTA/ DSC/TG), X-ray diffraction (XRD), and scanning electron microscopy (SEM/EDS) methods. One intermediate compound with formula Ca_3Ce(PO_4)_3 occurs in the Ca_3(PO_4)_2-CePO_4 system at temperature exceeding 1275℃. The compound melts at 1833℃ and has one structural form. In the system a solid solution, having the structure of low-temperature form of calcium phosphate Ca_(3-3x)Ce_x(PO_4)_(2-x) (where x is a molar fraction of CePO_4), exists. The temperature and concentration range of the solid solution has been determined. It has been shown that the Ca_9Ce(PO_4)_7 phase should be understood as a limited solid solution with x = 0.25.