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

Solid solution Zn2-2xCu2xSiO4 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 degrees C because of the decomposition of CuO. The extent of the Zn2-2xCu2xSiO4 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 Zn2-2xCu2xSiO4 samples in the homogeneity region are also independent of the dopant index x and close to the values found for undoped Zn2SiO4 (1512 +/- 1 degrees C). The deformation phase transition in Zn2SiO4 and Zn2-2xCu2xSiO4 is found for the first time being 10 +/- 2 degrees 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.