In-situ diffraction study of Ba2In2O5

In-situ neutron and X-ray diffraction experiments were used to determine the crystal structure of Ba2In2O5 as related to temperature. Ba2In2O5 has a Brownmillerite-type crystal structure from room temperature to 900 °C, consisting of an orthorhombic unit cell with lattice parameters 6.0864(3)×16.7903(7)×5.9697(3) Å and Icmm (74) space group symmetry. At 900 °C, oxygen vacancies begin to disorder. By 925 °C, barium indate crystallizes in a tetragonal, 6.0348(4)×17.0688(22) Å, unit cell with I4cm (108) space group symmetry. This oxygen vacancy order–disorder transition is associated with an evolution to fast oxide-ion conduction. At 1040 °C, Ba2In2O5 becomes a cubic oxygen-deficient perovskite, 4.2743(1) Å, in the Pm3m space group. At 1080 °C, Ba2In2O5 begins to decompose.