Nanostructured thermoelectric oxides with low thermal conductivity

Complex metal oxides, such as e.g. perovskite-type phases are developed as potential functional materials to improve the efficiency of thermoelectric converters. Among those, cobaltates with p-type conductivity and n-type manganates are considered for the realisation of a ceramic thermoelectric converter. Sintered pellets with the composition AMO3–δ (A = Ln, RE; M = Co, Mn, Ni, Ti) and “Ca3Co4O9 derivates” were synthesized and characterised concerning their thermoelectric properties in a broad temperature range. It was found that the Seebeck coefficient and the electrical conductivity do not depend on the dimensions of the crystallites, while the heat conductivity can be substantially lowered by decreasing the size of the crystalline domains in these systems. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)