Oxide-Ion Conduction, Average and Local Structures of LaSrGa1−xMgxO4−δ with Layered Perovskite Structure

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In this work, we prepared LaSrGa1−xMgxO4−δ with the K2NiF4-type layered perovskite structure and then investigated the electrical conduction property and the crystal structure. From the conductivity measurements, it was indicated that LaSrGaO4 exhibited oxide-ion conduction by substituting Mg for Ga partially, but the conductivity of the substituted sample was lower than those of LaGaO3-based materials reported previously. In order to clarify the reason of the lower conductivity, we performed the Rietveld and Pair Distribution Function (PDF) analyses using neutron scattering data, and also carried out first principle calculation as a theoretical approach. As a result, it was indicated the material had a two-dimensional oxide-ion conduction pathway and the oxygen vacancy tended to be localized at the corner sharing position of GaO6 within the perovskite layer. In addition, it was suggested that the low ionic conductivity in the LaSrGaO4-based materials were caused by a large distortion around the defect and a large repulsive force between the oxygen vacancy and La3+.