Tetrahedral Tilting and Oxygen Vacancy Stabilization and Migrationin La1-xSr2+x(GaO4)O1-0.5x Mixed Electronic/Oxide Ionic Conductors

The La2O3/SrO/Ga2O3ternary system contains severalcompounds with remarkable oxide or proton ionic conduction. Among them,the layered LaSr2(GaO4)O compound is a less commonly studied material.Here, the crystal structure, electrical conduction properties, and ionic migrationmechanism of the La1-xSr2+x(GaO4)O1-0.5x(0 <= x <= 0.3) system arethoroughly analyzed. Diffraction methods indicate that the system crystallizes inthe tetragonal space groupP4/ncc, which is compatible with the presence of asubtle GaO4tetrahedral tilting along thecaxis, leading to a slight deviation ofthe body-centered tetragonal structure previously reported. This feature isessential to further understanding the mixed p electronic/oxide ion-conductingbehavior of the system. Upon La3+for Sr2+substitution, oxygen vacancies ariseat the loosely bound oxide sublattice, which at high temperature go through theGaO4tetrahedral layer, leading to the formation of intermediate corner-sharingGa2O7tetrahedral dimers, and migrate via the continuous breaking and re-formation of the dimers, assisted by the synergic rotationand deformation of neighboring GaO4tetrahedra. The unique structural and electrical features of La1-xSr2+x(GaO4)O1-0.5xmaterialswithin the La2O3/SrO/Ga2O3ternary system emphasize their potential application as cathode materials in LaGaO3-based fuel cells

Automated summary

This study thoroughly analyzed the crystal structure, electrical conduction properties, and ionic migration mechanism of the La1-xSr2+x(GaO4)O1-0.5x system, laying the foundation for a better understanding of the mixed p electronic/oxide ion-conducting behavior of the system.