Low thermal conductivity of SrTiO3-LaTiO3 and SrTiO3-SrNbO3 thermoelectric oxide solid solutions

Electron-doped SrTiO3 has been attracting attention as oxide thermoelectric materials, which can convert wasted heat into electricity. The power factor of the electron-doped SrTiO3, including SrTiO3-LaTiO3 and SrTiO3-SrNbO3 solid solutions, has been clarified. However, their thermal conductivity (kappa) has not been clearly identified thus far. Only a high kappa (>12 W m(-1) K-1) has been assumed from the electron contribution based on Wiedemann-Franz law. Here, we show that the kappa of the electron-doped SrTiO3 is lower than the assumed kappa, and its highest ZT exceeded 0.1 at room temperature. The kappa slightly decreased with the carrier concentration (n) when n is below 4 x 10(21) cm(-3). In the case of SrTiO3-SrNbO3 solid solutions, an upturn in kappa was observed when n exceeds 4 x 10(21) cm(-3) due to the contribution of conduction electron to the kappa. On the other hand, kappa decreased in the case of SrTiO3-LaTiO3 solid solutions probably due to the lattice distortion, which scatters both electrons and phonons. The highest ZT was 0.11 around n = 1 x 10(21) cm(-3). These findings would be useful for the future design of electron-doped SrTiO3-based thermoelectric materials.

Automated summary

The study shows that the thermal conductivity of electron-doped SrTiO3 is lower than assumed, with the highest ZT exceeding 0.1 at room temperature. The impact of carrier concentration on thermal conductivity varies in different solid solutions, providing insights for the future design of electron-doped SrTiO3-based thermoelectric materials.