The electronic structure of fluorite-like ionic conductors:: Solid solutions in the ZrO2-In2O3, ZrO2-In2O3-Tl2O3, and ZrO2-In2O3-CaO systems

The close-coupling method is applied to calculate the band structure for 24-atomic supercells and study the electronic energy structure and the nature of chemical bonds in fluorite-like solid solutions of the ZrO2-In2O3, ZrO2-In2O3-Tl2O3, and ZrO2-In2O3-CaO systems. According to the quantum-chemical calculations, the stablest states are those of crystals containing heterovalent admixture (In, Tl, or Ca)-oxygen vacancy complexes in the bulk. The role played by these complexes in the nonlinear behavior of ionic conductivity and in phase transitions is discussed as depending on admixture concentrations. It is suggested that one of the possible phase transitions involves the formation of polytypes.