Thermoelectric oxides: important role of the transition metal spin states

During the search for new thermoelectric materials for high temperature energy conversion, the metal transition oxides have attracted much attention. Their principal advantage lies in the chemical stability under oxidizing atmosphere. Despite that numerous oxide phases exhibit large Seebeck (S) coefficient values (S >100muV.K^-1 ), low thermal conductivities (kappa ~ 1W.K^-1.m^-1), their performances are limited by their resistivity values higher than those of typical thermoelectric materials. Understanding the origin of the large S values of oxides is however a complex challenge. We propose to review the various physical behaviors by comparing several kinds of transition metal oxides for which the structural type governing the cobalt cation crystal field is at the origin of different physics