Development of high-temperature thermoelectric materials based on SrTiO3-layered perovskites

Abstract

Abstract For improving the performance of ceramic thermoelectric materials an increase in the effective mass is required because it is the main factor determining the Seebeck coefficient, in the case of a semiconductor with sufficiently high carrier concentration. The Ruddlesden–Popper phase Sr3Ti2O7, with its conducting perovskites layer in between the phonon absorbing SrO layers, is an example for advanced material design by nano-block integration. Using ab-initio simulations, the electronic bandstructure was calculated, and from the curvature of the bands the effective mass was deduced. While Sr3Ti2O7 has a smaller effective mass than the Nb-doped SrTiO3, the layered perovskites with substitution of Ta instead of Ti possess very large effective masses (m*/m0=9 in average) and a large thermopower is expected. In the experiments, however, the sufficient charge carrier concentration could not yet be reached.