Thermoelectric properties of Ba3Co2O6(CO3)0.7 containing one-dimensional CoO6 octahedral columns

The thermoelectric properties of Ba3Co2O6(CO3)0.7 have been investigated using prismatic single crystals elongated along the c axis. Ba3Co2O6(CO3)0.7 has a pseudo-one-dimensional structure similar to that of 2H perovskite-type BaCoO3 and contains CoO6 octahedral columns running parallel to the c axis. The prismatic crystals are grown by a flux method using a K2CO3–BaCl2 flux. The electrical conductivity (σ) along the columns (c axis) exhibits a metallic behavior (670–320 S cm−1 in the temperature range of 300–1100 K), whereas the temperature dependence of the electrical conductivity perpendicular to the c axis is semiconducting. The Seebeck coefficient (S) along the columns is positive and greater than 100 μV K−1 over the measured temperature range (116–128 μV K−1). Ba3Co2O6(CO3)0.7 shows power factors (σS2) of 5.5×10−4–9.0×10−4 W m−1 K−2 above room temperature, relatively high values for an oxide material.