Current energy consumption has great impact on the environment and human life. Hence alternative sources as well as improve conversion are massively explored. Waste-heat recovery is feasible using thermoelectric devices but still of limited commercial use due to the low energy conversion efficiency of present thermoelectric (TE) materials. The figure of merit is a measure of the TE performance of TE materials and can be increased by means of band engineering or nanostructuring. Compared to the current generation (i.e. chalcogenites and skutterudites) of TE materials, oxides became promising candidates due to their wide-range doping, offering lower toxicity, higher stability at high temperature and durability. Our research uses a combination of ab initio both plane-wave and all-electron techniques, to engineer the band structure of the perovskite CaMnO3. In principle, this can be applied to any oxide used for TE devices. We find that precisely engineered doping can have a great effect on the band structure of the material and can be used to tune the thermoelectric properties. We first present the effect of oxygen vacancy ordering on the electronic transport properties of CaMnO3. As the concentration of oxygen vacancies increases the band structure can be tuned to modify the Seebeck coefficient as well as the electronic conductivity. Secondly, we describe the effect of extrinsic defects achieved by co-doping with Sr and Mo or Nb. This introduces localized state on the Mn site and may be an alternative route to oxygen vacancy doping.

Waste-heat recovery from thermoelectric materials

247th National Meeting (2014)

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