Novel structural features and phase transition behaviour of (Sr_1-xCa_x)TiO₃: I. Neutron diffraction study

Abstract

Superlattice reflections observed for the first time in the room temperature powder neutron diffraction patterns of SCT are shown to arise due to tilting of TiO6 octahedra. Rietveld refinement of the neutron diffraction data confirms that the structure of SCT for is orthorhombic similar to that of CaTiO3. Implications of the presence of tilted TiO6 octahedra and the associated off-centre displacements of Sr3+/Ca2+ in SCT are discussed in detail with regard to the quantum ferroelectric behaviour of SCT at low temperatures. Structural phase transitions in SCT with x = 0.06 and 0.12 are also reported.