Triangulation in the Li₂ZnP₂O₇–Na₂ZnP₂O₇–K₂ZnP₂O₇ System

Abstract—The topicality of studies into phase equilibria of phosphate systems involving alkali elements and zinc is due to their potential for use as catalysts, ionic conductors, luminophores, solid-state lasers, piezoelectric and other materials whose properties are valuable for practice. Phase formation in LiNaZnP₂O₇–NaKZnP₂O₇ and LiNaZnP₂O₇–K₂ZnP₂O₇ particular sections of the Li₂ZnP₂O₇–Na₂ZnP₂O₇–K₂ZnP₂O₇ ternary system has been studied by X-ray powder diffraction on samples prepared by solid-phase synthesis. The body of data on phase equilibria in previously studied ${\text{М}}_{2}^{'}$ZnP₂O₇–ZnP₂O₇ (M', M" = Li, Na, K) and LiKZnP₂O₇–LiNaZnP₂O₇ (NaKZnP₂O₇, Na₂ZnP₂O₇) systems and the data obtained in this work have been used to triangulate the Li₂ZnP₂O₇–Na₂ZnP₂O₇–K₂ZnP₂O₇ ternary system in the area confined to compounds Na₂ZnP₂O₇, LiNaZnP₂O₇, LiKZnP₂O₇, and K₂ZnP₂O₇. Solid solutions involving up to three alkali metals were found to exist therein: NaKZnP₂O₇-base solid solutions Li_xNa_yK_{2 – (x + y)}ZnP₂O₇ (0 ≤ x ≤ 0.8, 0.2 ≤ y ≤ 1.0) (space group P2₁/n) and K₂ZnP₂O₇-base solid solutions Li_xNa_yK_{2 – (x + y)}ZnP₂O₇ (0 ≤ x ≤ 0.17, 0 ≤ y ≤ 0.42) (space group P4₂/mnm). A revised Li₂ZnP₂O₇–K₂ZnP₂O₇ phase diagram was plotted as a result of this study.