Effects of yttrium substitution and oxygen deficiency on the crystal phase, microstructure, and thermoelectric properties of Sr1−1.5xYxTiO3−δ (0 ⩽ x ⩽ 0.15)

• We studied the thermoelectric properties of Sr1−1.5xYxTiO3−δ (0 ⩽ x ⩽ 0.15).
• The figure of merit (ZT) was increased with increasing x when 0.02 ⩽ x < 0.08.
• The Y2Ti2O7 existed in samples with 0.08 ⩽ x ⩽ 0.15.
• Y2Ti2O7 causes a decrease in the thermal conductivity.
• Sr0.88Y0.08TiO3−δ exhibited the highest ZT of ∼0.20 at 680 °C.

The phase composition, microstructural and thermoelectric properties of n-type Sr1−1.5xYxTiO3−δ (0 ⩽ x ⩽ 0.15) have been investigated over the temperature range of 50 °C ⩽ T ⩽ 680 °C. The electrical conductivity increased with increasing x, while the absolute values of the Seebeck coefficient decreased with increasing x in the range of 0.02 ⩽ x < 0.08. A further increase in x (x ⩾ 0.08) led to the formation of Y2Ti2O7. The existence of Y2Ti2O7 had no effect on the Seebeck coefficient; however, it did result in a larger decrease in the electrical conductivity than the thermal conductivity. Consequently, the thermoelectric performance of Sr1−1.5xYxTiO3−δ was reduced with increasing amount of Y2Ti2O7. Sr0.88Y0.08TiO3−δ exhibited the highest thermoelectric figure of merit (ZT) of ∼0.20 at 680 °C.