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Tetrahedral Tilting and Oxygen Vacancy Stabilization and Migration in La1-Sr2+(GaO4)O1-0.5 Mixed Electronic/Oxide
Jiachen Li1, Li Yang1, Jungu Xu1
1MOE Key Laboratory of New Processing Technology for Nonferrous Metals and Materials, Guangxi Key Laboratory of Optical and Electronic Materials and Devices, Guangxi Universities Key Laboratory of Nonferrous Metal Oxide Electronic Functional Materials and Devices, and College of Materials Science and Engineering, Guilin University of Technology, Guilin 541004, P. R. China.
Abstract:
The La2O3/SrO/Ga2O3 ternary system contains several compounds 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 migration mechanism of the La1-Sr2+(GaO4) O1-0.5 (0 ≤ x ≤ 0.3) system are thoroughly analyzed. Diffraction methods indicate that the system crystallizes in the tetragonal space group P4/ncc, which is compatible with the presence of a subtle GaO4 tetrahedral tilting along the c axis, leading to a slight deviation of the body-centered tetragonal structure previously reported. This feature is essential to further understanding the mixed p electronic/oxide ion-conducting behavior of the system. Upon La3+ for Sr2+ substitution, oxygen vacancies arise at the loosely bound oxide sublattice, which at high temperature go through the GaO4 tetrahedral layer, leading to the formation of intermediate corner-sharing Ga2O7 tetrahedral dimers, and migrate via the continuous breaking and re-formation of the dimers, assisted by the synergic rotation and deformation of neighboring GaO4 tetrahedra. The unique structural and electrical features of La1-Sr2+(GaO4)O1-0.5 materials within the La2O3/SrO/Ga2O3 ternary system emphasize their potential application as cathode materials in LaGaO3-based fuel cells.
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