Synthesis, crystal structure and magnetic properties of Ba5Ru2O9(O2), Ba5Nb2O9(O2) and Ba5Ru2O10 related to the perovskite-type structure, and structural relationships with corresponding sulfides

Abstract

The compound Ba 5 Nb 2 O 9 (O 2 ) has been synthesized by solid state reactions. The crystal structure has been refined from X-ray powder data. Ba 5 Nb 2 O 9 (O 2 ) is isostructural with Ba 5 Ru 2 O 9 (O 2 ) with the cell parameters a =6.045(1)Å, c =18.316(3)Å (P6 3 /mmc). Perpendicular to the c -axis, the structure is built up by the periodic stacking of three close packed [BaO 3 ] layers separated by a layer of composition [Ba 2 O 2 ] containing (O 2 ) 2− peroxide ions. The compound Ba 5 Ru 2 O 10 has been obtained by thermal decomposition of Ba 5 Ru 2 O 9 (O 2 ). The structure has been refined from X-ray powder data. The structure is similar to Ba 5 Ru 2 O 9 (O 2 ) but now the composition of the layer is [Ba 2 O]. The magnetic properties of Ba 5 Ru 2 O 9 (O 2 ) and Ba 5 Ru 2 O 10 have been interpreted in terms of isolated dimers and confirm the structural results. All these phases belong to a new family of compounds formulated as [A 2 (O 2 )][A n B n −1 O 3 n ] where n represents the number of [AO 3 ] successive layers in the hexagonal perovskite slabs. This series is extended to ternary barium sulfides.