Symmetry-mode analysis of the phase transitions in SrLaZnRuO6and SrLaMgRuO6ordered double perovskites

Abstract

The crystal structures of double perovskites SrLaMRuO6(M= Zn and Mg) have been studied using X-ray and neutron diffraction data. Both compounds have monoclinic structure at room temperature with space groupP21/n. A first-order structural phase transitionP21/n→R{\overline 3} has been observed in SrLaZnRuO6and SrLaMgRuO6, at about 800 and 500 K, respectively, with the two phases coexisting in a temperature interval of 150 K. The temperature- and tolerance-factor-dependent phase diagram of the SrLnMRuO6(Ln = La, Nd and Pr;M= Zn, Co, Cu, Mg and Ni) family shows two different phase transition sequences depending on theA-site cation. The structures of the title compounds at room and high temperatures have been analyzed using the symmetry-mode decomposition approach.