Phase relations in the system Na₂ZnP₂O₇-Zn₂P₂O₇

Abstract

Data on phase relations in the system Na₂ZnP₂O₇-Zn₂P₂O₇ reported in the literature are scarce and contradictory. The system was first studied by Berul and Voskresenskaya [Russ. J. Inorg. Mater. (English transl.) 4 (12), 2129 (1968)], who established the existence of a congruently melting intermediate compound, Na₈Zn₆(P₂O₇)₅. In the paper by Majling et al. [Chem. Zvesti. 28 (3), 294 (1974)], the system Na₂ZnP₂O₇-Zn₂P₂O₇ is considered to be eutectic. The subsolidus phase relations are represented by a mixture of two phases, terminal members of the system. The existence of the above-mentioned compound was not confirmed for this system. In the present work we studied the phase relations in the system Na₂ZnP₂O₇-Zn₂P₂O₇ on samples obtained by solid-state synthesis and glass crystallization. The sequence of crystallization of phases was investigated, and the equilibrium and metastable phase diagrams were constructed for the system.