STRUCTURES AND PHASE TRANSITION IN THE LAYERED PEROVSKITE La_0.6Sr_0.1TiO₃

Christopher J. Howard and Zhaoming Zhang

Materials and Engineering Science, Australian Nuclear Science and Technology Organisation, Private Mail Bag 1, Menai, NSW 2234, Australia (cjh@ansto.gov.au)

The crystal structure of the layered perovskite La_0.6Sr_0.1TiO₃ at room temperature has been solved by synchrotron X-ray powder diffraction in combination with group theoretical analysis. The structure is orthorhombic in Cmmm, on a cell with a = 7.7556(1), b = 7.7349(1), c = 7.7910(1) Å. It is believed that this is the structure also adopted by La_2/3TiO₃. Pertinent features are the alternation of fully and partly occupied layers of La (Sr) cations, and out-of-phase tilting of the TiO₆ octahedra around an axis perpendicular to the direction of the cation ordering. The compound undergoes a second order transition to a tetragonal structure, the transition temperature being estimated as 360 ºC.