Phase Equilibria in the Ternary System MgO-Na2O-P2O5. The Partial System Mgo-Na3PO4-Na4P2O7

Apartial system of MgO-Na3PO4-Na4P2O7 in the ternary system MgO-Na2O-P2O5 was investigated and its phase diagram was obtained. Thermal analysis (heating and cooling), powder X-ray diffraction, and optical microscopy using reflected light were applied. In the composition range of interest two ternary compounds occur, which melt congruently and have the formulae MgNa4(PO4)2 (m.p. 1655°C) and MgNa6P2O9 (m.p. 1665°C). The phosphates compose a quasi-binary section with continuous solid solutions and exhibit a temperature minimum about 1520°C.