Phase Equilibria and Chemical Reactions in the Mn₂O₃–ZnO–SiO₂, Mn₃О₄–ZnO–SiO₂, and MnO–ZnO–SiO₂ Systems

Abstract

The subject matter of this work was the triangulation of the Mn₂O₃–ZnO–SiO₂, Mn₃O₄–ZnO–SiO₂, and MnO–ZnO–SiO₂ systems and the determination of phase transformations to yield Zn_{2 – 2х}Mn_2хSiO₄ solid solution. Equilibrium phase diagrams have been plotted taking into account the existence temperatures of each of the manganese oxides, phase compositions of the constituent binary systems, and checkup points, whose phase compositions helped us to determine the positions of secondary triangles. The phase compositions of reaction products of the terminal oxides and the phase transformation sequence during Zn_{2 – 2х}Mn_2хSiO₄ synthesis were monitored by X-ray powder diffraction and thermal analysis. Phase ratios in the MnO_х–ZnO–SiO₂ system are caused by the charge states of manganese ions changing in response to rising temperature. The triangulation of the Mn₂O₃–ZnO–SiO₂ system at 800°С is determined by the ZnMn₂O₄–Zn₂SiO₄ tie-line and partitions the system to the ZnO–Zn₂SiO₄–ZnMn₂O₄, Zn₂SiO₄–ZnMn₂O₄–SiO₂, and ZnMn₂O₄–SiO₂–Mn₂O₃ simplex triangles. The Zn_{2 – 2х}Mn_2хSiO₄ solid solution with an extent limited to Zn_1.6Mn_0.4SiO₄ is formed at temperatures above 1000°С. The triangulation of the MnO–ZnO–SiO₂ ternary system is determined by the Zn_1.6Mn_0.4SiO₄–ZnO–MnSiO₃ simplex triangle.