Synthesis and Characterization of the First 1:2 Ordered Perovskite Ruthenate
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Synthesis and Characterization of the First 1:2 Ordered Perovskite Ruthenate Job Rijssenbeek,1 Sylvie Malo,2 Takashi Saito,3 Vincent Caignaert,2 Masaki Azuma,3 Mikio Takano,3 Kenneth R. Poeppelmeier.1 1 Department of Chemistry, Northwestern University, Evanston, IL 60208-3113 2 Laboratoire CRISMAT-ISMRA, Université de Caen, 6 Boulevard du Maréchal Juin, 14050 Caen, Cedex, France 3 Institute for Chemical Research, Kyoto University, Uji, Kyoto-fu 611, Japan ABSTRACT Perovskite-like mixed metal ruthenates are of interest owing to their varied electronic and magnetic properties, which are heavily dependent on the ordering of the transition metals. We report the synthesis and structural characterization of the first 1:2 ordered perovskite ruthenate, Sr3CaRu2O9. The structure was determined from a combination of powder X-ray, electron and neutron diffraction data and is characterized by a 1:2 ordering of Ca2+ and Ru5+ over the sixcoordinate B-sites of the perovskite lattice. Sr3CaRu2O9 is the first example of this structure-type to include a majority metal with d electrons (Ru(V), d3). The relationship of this material to the K2NiF4-type Sr1.5Ca0.5RuO4 (i.e., Sr3CaRu2O8) highlights the dramatic effects of the ruthenium valence on the resultant structure. Remarkably, these two structures can be quantitatively interconverted by the appropriate choice of reaction temperature and atmosphere.
INTRODUCTION The perovskite structure (Fig. 1d) is exceedingly simple, as reflected by its general chemical formula ABX3-δ, yet it possesses a chemical and structural flexibility unmatched by any other structure type. Fully 80% of all elements can be incorporated within perovskite-like architectures. This remarkable chemical malleability endows perovskite materials with an extraordinarily wide variety of properties. Furthermore, when multiple cations occupy the B-site, the degree and type of ordering determines, in large part, the electrical and/or magnetic properties of the material. Therefore, an understanding of order/disorder phenomena is of great interest with respect to the potential applications of perovskites, including superconductivity, magneto-resistance, dielectric behavior, etc.
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Figure 1. Different B-site ordering patterns in perovskite. (a) 1:1 ordered Sr2YRuO6 (ref 18); (b) 1:2 ordered Ba3ZnTa2O9 (ref. 12); (c) 1:3 ordered Ba4LiSb3O12 (ref. 3); (d) perovskite SrRuO3 (ref. 17). D1.3.1 Downloaded from https:/www.cambridge.org/core. University of Arizona, on 26 Apr 2017 at 13:15:57, subject to the Cambridge Core terms of use, available at https:/www.cambridge.org/core/terms. https://doi.org/10.1557/PROC-718-D1.3
The most common type of B-site ordering is found in double perovskites,1 A2BB'O6, wherein the B-cations form a 1:1 ordered rock-salt type lattice (Fig. 1a). When the cation ratio is not 1:1, other types of ordering are possible. For example, A3B'B2O9 and A4B'B3O12 compounds can adopt 1:2 and 1:3 ordered structures, respectively (Fig. 1b and 1c).2,3 Such orderings are relatively rare and have, un
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