Thermoelectric phase diagram of the SrTiO3-LaTiO3 solid-solution system through a metal to Mott insulator transition

Abstract

Systematic clarification of thermoelectric properties of a solid-solution system is essentially important, especially if the materials have different crystal and electronic structures. Here, we report the thermoelectric phase diagram of the full-range Sr1 − xLaxTiO3 solid solutions composed of a band insulator SrTiO3 (cubic perovskite) and a Mott insulator LaTiO3 (distorted perovskite), which shows the room temperature thermoelectric power factor changing pattern with the La substitution (x) in the SrTiO3 system. We measured the room temperature thermoelectric properties of Sr1 − xLaxTiO3 (0.01 ≤ x ≤ 1) epitaxial films grown by the pulsed laser deposition and found that there are two thermoelectric phase boundaries at x ∼ 0.5 and x ∼ 0.7 in the Sr1 − xLaxTiO3 system. The former is attributed to the lattice distortion from cubic to orthorhombic variation, whereas the latter is due to the electronic phase transition from metal to Mott insulator. The thermoelectric phase diagram obtained in our study will be fruitful for the future design of n-type thermoelectric materials based on the electron-doped SrTiO3.