Perovskite manganites and layered cobaltites:: potential materials for thermoelectric applications

Metal-transition oxides are potential materials for thermoelectric devices operating at high temperatures (Tmuch greater than 300 K). In particular, compounds exhibiting small resistivity and large Seebeck coefficient are required. Two kinds of oxides have been retained: the 'misfit' cobaltites which are p-doped metallic phases and the electron doped perovskite manganites. For the former, it is found that the Ca for Sr substitution enhances the thermopower values in the Pb/Sr/Co/O misfit cobaltite whereas it has only a moderate effect in the case of the Tl/Sr/Co/O phase. From this study, it appears that the oxidation state of Co in the conducting layers plays a crucial role on the physical properties. Moreover, for the manganites, we show that electron-doped SrMnO3 can be prepared by a two-steps method. The doping, created via substitution at either the A-site (Pr3+ for Sr2+) or B-site (Mo6+ for Mn4+), leads to metallic compounds with large thermopower values. (C) 2003 Elsevier Science Ltd. All rights reserved.