Crystal structures and phase transitions in Sr doped Ba2InTaO6 perovskites

Abstract

The crystal structures of the double perovskites of the type Ba2-xSrxInTaO6 have been studied by synchrotron X-ray and neutron powder diffraction methods. The structures are based on ordered array of the tilted InO6 and TaO6 octahedra, with the Ba/Sr cations being completely disordered. The structure evolves from cubic to monoclinic Fm (3) over barm(x similar to 0) (6)-> I4/m(x similar to 1.2)-> I2/m(x similar to 1.6)-> P2(1)/n. The changes in the symmetry induced by replacing the Ba with Sr have been identified by a symmetry-mode analysis. Variable temperature S-XRD studies of selected examples have shown that heating the samples induces the same sequence of transitions observed in the composition dependent studies. © 2013, Elsevier Ltd.