Novel structural features and phase transition behaviour of (Sr1-xCax)TiO3: I. Neutron diffraction study

Abstract

Superlattice reflections observed for the first time in the room temperature powder neutron diffraction patterns of SCT (Sr1-xCaxTiO3, x ≥ 0.12) are shown to arise due to tilting of TiO6 octahedra. Rietveld refinement of the neutron diffraction data confirms that the structure of SCT for x ≥ 0.12 is orthorhombic similar to that of CaTiO3. Implications of the presence of tilted TiO6 octahedra and the associated off-centre displacements of Sr2+/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. © 1999 IOP Publishing Ltd.