Abstract
Owing to their vast chemical and structural flexibility, crystalline perovskite-type metal oxides (ABO ) are amongst the most promising solid electrolytes for use in all-solid-state batteries for large scale energy storage applications. The perovskite-type sodium-ion solid electrolyte series Na La Sr ZrO have the highest reported ionic conductivities, and we re-examine their room temperature crystal structures using X-ray and high-resolution neutron powder diffraction. In contrast to a previous report, four members of the series, x = 1/16, 1/8, 1/6, and 1/4, were found to adopt orthorhombic symmetry with the space group Pbnm. Variable temperature neutron diffraction data (room temperature to 1100 °C) were used to probe temperature-dependent structural changes for the member of the series with the highest reported ionic conductivity (x = 1/6). A phase transition from orthorhombic Pbnm to tetragonal I4/mcm was identified at 800 °C. 3 1/2-x 1/2-x 2x 3