A-Site Deficient SrTiO₃: A Possible Phonon-Glass Electron-Crystal?

The thermoelectric properties of polycrystalline samples of Sr1-xLa0.67xTiO3-δ and Sr0.20La0.53Ti1−yNbyO3-δ have been investigated. The first series has a gradually increasing amount of A-site vacancies, and charge carriers linked to the oxygen deficiency. The second series has a fixed amount of A-site vacancies (27%) and variation of the Nb content was used to optimise the electrical properties. Maximum power factors of 0.6 mW m-1 K-2 for x = 0.4 and 0.4 mW m-1 K-2 for y = 0.05 were observed at 700 K. Combining these values with thermal conductivity data obtained previously, suggests that maximum figures of merit zT = 0.16 for x = 0.4 and zT = 0.2 for y = 0.05 are possible at 1000 K. This study contributes new insight on the interplay between A-site vacancies and thermoelectric performance in SrTiO3.