Synthesis, Crystal and Thermal Properties of Solid Solution Zn2−2xCu2xSiO4 with Willemite Structure

Abstract

Solid solution Zn_2−2xCu_2xSiO₄ with the willemite structure has been synthesized by the proposed solid-phase synthesis procedure. It is shown that the maximum annealing temperature is 1030 ± 1°C because of the decomposition of CuO. The extent of the Zn_2−2xCu_2xSiO₄ solid solution is 7.5 at % Cu. The unit cell crystal-chemical parameters and coefficients of thermal linear and volume expansion are independent of the Cu²⁺ concentration. Melting points of Zn_2−2xCu_2xSiO₄ samples in the homogeneity region are also independent of the dopant index x and close to the values found for undoped Zn₂SiO₄ (1512 ± 1°C). The deformation phase transition in Zn₂SiO₄ and Zn_2−2xCu_2xSiO₄ is found for the first time being 10 ± 2°C below the melting point. The combination of the obtained crystal-chemical and thermal data allowed us to carry out the triangulation of the diagram of the ZnO−SiO₂−CuO system to divide it into five secondary triangles by two-phase equilibria lines.