Crystal structures and high-temperature phase-transitions in SrNdMRuO6 (M=Zn,Co,Mg,Ni) new double perovskites studied by symmetry-mode analysis

Abstract Crystal structures of SrNdZnRuO 6 , SrNdCoRuO 6 , SrNdMgRuO 6 and SrNdNiRuO 6 double perovskites have been studied by X-ray, synchrotron radiation and neutron powder diffraction method, at different temperatures, and using the symmetry-mode analysis. All compounds adopt the monoclinic space group P 2 1 / n at room-temperature, and contain a completely ordered array of the tilted M O 6 and RuO 6 octahedra, whereas Sr/Nd cations are completely disordered. The analysis of the structures in terms of symmetry-adapted modes of the parent phase allows the identification of the modes responsible for the phase-transition. The high-temperature study (300–1250 K) has shown that the compounds present a temperature induced structural phase-transition: P 2 1 / n → P 4 2 / n → Fm 3 ¯ m .