Li4GeO4-Li2CaGeО4 phase equilibria and Li2+xCa1-xGeO4 solid solutions

Detailed studies of the Li4GeО4-Li2CaGeО4 system by solid-phase syntheses of various compositions from pure Li4GeО4 to pure Li2CaGeО4 in the temperature range from 25 to 1125 °C is investigated for a first time. Solid state synthesis powders are characterized by X-ray and DSC/TG methods. Concentration and temperature two-phase regions of Li4GeО4 and Li2CaGeО4 as well as two-phase regions of Li2CaGeО4 and Li2+2xCa1-xGeO4 are established. Region of pure Li2+2xCa1-xGeO4 solid solution are detected too and it structure is investigated. Being structural analog to Li2+2xZn1-xGeO4 and Li2+2xMg1-xGeO4, Li2+2xCa1-xGeO4 has own specific local environment of the metal ions. The obtained results are compared with those for Li4GeО4-Li2ZnGeО4 system and for Li2+2xZn1-xGeO4 solid solution. The differences of the phase diagrams and structural features of the solid solutions are discussed.