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

Crystal structures of SrNdZnRuO6, SrNdCoRuO6, SrNdMgRuO6 and SrNdNiRuO6 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 P21/nP21/n at room-temperature, and contain a completely ordered array of the tilted MO6 and RuO6 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: P21/n→P42/n→Fm3¯m.

Graphical abstractRepresentation of the dominant distortion modes of the symmetry mode decomposition of the room-temperature (P21/n)(P21/n), intermediate (P42/n)(P42/n) and cubic (Fm−3m)(Fm−3m) phase SrNdMRuO6 (M  =Zn,Co,Mg,Ni), with respect to the parent phase Fm−3mFm−3m. The dominant distortion modes are: in the monoclinic phase—GM4+ (blue arrow), X3+ (green arrow) and X5+ acting on A  -site cations (red arrow); in the tetragonal phase—GM4+ (pink arrow), X3+ (light blue arrow) and X5+ acting on A-site cations (brown arrow).Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Structural study of four ruthenate double perovskites. ► Room-temperature structural determination using symmetry-mode procedure. ► Determination of temperature induced structural phase-transitions. ► Symmetry adapted-mode analysis.