New route to ordered double perovskites: synthesis of rock salt oxides, Li₄MWO₆, and their transformation to Sr₂MWO₆ (M= Mg, Mn, Fe, Ni) via metathesis

Abstract

We describe a solid-state metathesis route for the synthesis of double perovskite oxides, Sr₂MWO₆ (M = Mg, Mn, Fe, Ni), that enabled us to obtain cation-ordered phases at a considerably lower temperature ( ~750°C) than what is employed in conventional synthesis of these materials. The method involves reaction of appropriate rock salt related precursor oxides of the formula Li₄MWO₆ with anhydrous SrCl₂ in the solid state at 750°C for 1-2 days. For this purpose, rock salt precursor oxides were designed and synthesized for the first time. Cation ordering in the Sr₂MWO₆ products obtained was investigated by Rietveld refinement of powder X-ray diffraction data. We believe that the strategy described here is general and could be extended for the synthesis of functional double perovskites at relatively mild conditions.