Structures of the cation-deficient perovskite Nd_0.7Ti_0.9Al_0.1O₃ from high-resolution neutron powder diffraction in combination with group-theoretical analysis

The room-temperature structure of the cation-deficient perovskite, Nd_0.7Ti_0.9Al_0.1O₃, with layered ordering of cations/vacancies on the A-site, involves octahedral tilting around two axes. Tilting around the axis parallel to the direction of the layered cation/vacancy ordering disappears above ca 750 K, the only tilt persisting at higher temperature being about a single axis perpendicular to this direction.