The related parameters of cation size and valence that control the crystallization of Sr3CaRu2O9 into a 1:2 B-site-ordered perovskite structure were explored by cationic substitution at the strontium and calcium sites and by the application of high pressure. At ambient pressures, Sr3MRu2O9 stoichiometries yield multiphasic mixtures for M = Ni2+, Mg2+, and Y 3+, whereas pseudocubic perovskites result for M = Cu2+ and Zn2+. For A-site substitutions, an ordered perovskite structure results for Sr3-xCaxCaRu2O9, with 0 ≤ x ≤ 1.5. In contrast, Ba2+ substitution for Sr2+ is accompanied by a phase change to a hexagonal BaTiO3 structure type. At high pressures and temperatures, a 1:2 B-site-ordered perovskite structure is stabilized for Sr3-xBaxCaRu2O 9, with 0 ≤ x ≤ 3. The scarcity of B-site-ordered perovskite ruthenates at ambient pressure and the metastable nature of the high-pressure phases underscore the strict size and valence requirements that must be met by the constituent cations to achieve these uncommon ordered structures.
ASJC Scopus subject areas
- Colloid and Surface Chemistry