Structural and semiconductor-to-metal transitions of double-perovskite cobalt oxide Sr2-xLaxCoTiO6-δ with enhanced thermoelectric capability

The thermoelectric properties of double-perovskite oxide Sr2-xLaxCoTiO6-delta were revealed to vary anomalously with the La concentration, plausibly due to a structural transition found in this study. Although the temperature dependence of the resistivity and thermopower of the present oxide showed a semiconductor-to-metal transition similar to those observed for other perovskite-related Co oxides such as Sr1-xYxCoO3-delta, the transition temperature was more than 350 K higher, implying considerable stabilization of the low-spin state of Co ions in the double-perovskite oxide. Consequently, the operating temperature range of the oxide for potential thermoelectric applications was significantly expanded toward higher temperatures. (C) 2011 American Institute of Physics. [doi:10.1063/1.3623476]