Investigation of phase equilibria in the Er2O3–Na2O–P2O5 system: the partial system ErPO4–NaPO3–Er(PO3)3

Abstract

The partial system ErPO 4 -NaPO 3 -Er(PO 3 ) 3 of the Er 2 O 3 -Na 2 O-P 2 O 5 oxide system has been investigated by thermoanalytical methods and X-ray powder diffraction. On the basis of the obtained results the phase diagram of the partial system is proposed. The system is bounded by three subsystems: (i) ErPO 4 -Er(PO 3 ) 3 , (ii) Er(PO 3 ) 3 -NaPO 3 and (iii) ErPO 4 -NaPO 3 . Their phase diagrams are proposed. In the Er(PO 3 ) 3 -NaPO 3 subsystem an intermediate compound NaEr(PO 3 ) 4 occurs; it melts incongruently at 655°C. It was found that ErPO 4 and NaEr(PO 3 ) 4 form a section which is a real system only in the subsolidus region (below 646°C). Two ternary invariant points (one ternary peritectic and one ternary eutectic) occur in the investigated partial system ErPO 4 -NaPO 3 -Er(PO 3 ) 3 .

The revised phase diagram of the Ca3(PO4)2–YPO4 system. The temperature and concentration range of solid-solution phase fields

“…Phase diagrams of phosphate systems with rare earth elements have been studied by our group in last decades [34][35][36][37][38][39]. In the Ca 3 (PO 4 ) 2 -REPO 4 systems (RE = Y, La, Ce) form compounds with the formula Ca 3 RE(PO 4 ) 3 [34][35][36].…”