Synthesis and properties of the structurally one-dimensional cobalt oxide Ba1-xSrxCoO3 (O <= x <= 0.5)

The hexagonal perovskite solid solution Ba1-xSrxCoO3 (0 less than or equal to x less than or equal to 0.5) was synthesized by treatment of cubic perov skite precursors at 500 degrees C in high-pressure oxygen. The structure co nsists of parallel chains of face-sharing CoO6 octahedra and alkaline-earth ion separators. All materials were found to be semiconducting. Seebeck coe fficient measurements indicate that transport is by both electrons and hole s. The slopes of the magnetic susceptibility vs temperature data suggest th at Co is in the low-spin S = 1/2 electronic configuration. The positive Cur ie-Weiss Theta(w)'s indicate a predominantly ferromagnetic spin interaction , and a complex magnetic state is seen at low temperature in the temperatur e- and held-dependent magnetic data. (C) 1999 Academic Press.