Thermoelectric properties of A-site deficient reduced Sr0.775La0.15-xEuxTiO3-δ (0 ≤ x ≤ 0.15)

There are numerous different schemes to improve the figure of merit (ZT) in oxide thermoelectrics, including creating additional electrons using oxygen vacancies, chemical doping, and A-site nonstoichiometry. A-site deficient (Sr,La)0.925TiO3- δ has shown promise as an n-type oxide thermoelectric; herein, additional A-site substitutional doping with Eu was used to improve ZT, through a combination of A-site size mismatch and non-stoichiometry. A solid solution series Sr0.775La0.15-xEuxTiO3-δ (0 ≤ x ≤ 0.15) was synthesised, showing a modest improvement in thermoelectric properties for x = 0.05, with a ZT of 0.18 at 600 °C, vs a ZT of 0.16 in the end member composition. Upon full characterisation, the additional electrons provided by the formation of oxygen vacancies were being used up by reduction of the added europium dopants, leading to a drop in electrical conductivity, and correspondingly, ZT. This gives a useful perspective in choosing dopants for schemes such as these.