Inter-relationship between crystal symmetry and ionic conductivity in doped LaGaO3

Pure and Sr/Mg doped LaGaO3 were synthesized by standard ceramic process. Their electrical conductivity and crystal symmetry were investigated by dc four-probe and Raman spectroscopy, respectively. Raman analysis revealed rhombohedral structure in La0.9Sr0.1Ga0.9Mg0.1O2.9 (LSGM1010) and LaGa0.8Mg0.2O2.9 (LGM20), while detected orthorhombic symmetry in La0.8Sr0.2GaO2.9 (LSG20) and pure LaGaO3. Electrical measurement found that LSGM1010 and LGM20 have similar ionic conductivity, which is higher than that of LSG20. The experimental results strongly indicate that high ionic conductivity prefer high symmetry in doped LaGaO3. An attempted explanation was offered to illustrate the interesting phenomena based on XPS study.