Ca2−xLi2xGeO4 solid solutions. Chemical composition range and flux crystal growth

Abstract

A series of Ca2−xLi2xGeO4 specimens with 0 < 2x < 2, were synthesized by the classical solid state method. X-ray analysis revealed that for 0 < 2x < 0.6 only Ca2−xLi2xGeO4 solid solutions of Ca2GeO4 structure crystallized. The cell parameters of these solid solutions linearly decreased upon increasing the lithium concentration, which means that the solutions are in accordance with the Vegard's law. For 2x > 0.6 the specimens contained two phases: (i) Ca2−xLi2xGeO4 solid solutions with maximum lithium concentration approximately equal to that for 2x = 0.6 and minimum values of the cell parameters and (ii) Li2CaGeO4 phase. Li2O·MoO3–Ca2GeO4 high-temperature solutions were used to grow Ca2−xLi2xGeO4 solid solutions and Li2CaGeO4 single crystals by the high temperature solution (flux) method. Li2CaGeO4 crystals were grown in the concentration range 8–26 wt. % Ca2GeO4 in the temperature range 830–980 °C. Crystals with chemical compositions of the Ca2−xLi2xGeO4 solid solutions with different Li concentrations were grown in the concentration range 26–40 wt. % Ca2GeO4 in the temperature range 980–1090 °C.