Fabrication and thermoelectric properties of Sr1 − xSixMnO3 − δ

•The addition of SiO2 to SrMnO3 − δ leads to a marked increase in electrical properties.•The substituted Si4 + yields a significant decrease in thermal conductivity.•Sr1 − xSixMnO3 − δ is a promising thermoelectric material for power generation.

The effect of Si4 + content on the microstructure and thermoelectric properties of Sr1 − xSixMnO3 − δ (0.05 ≤ x ≤ 0.3) samples is discussed. For x ≤ 0.15, the substitution of Si4 + for Sr2 + leads to a significant increase in electrical conductivity and a decrease in the absolute value of the Seebeck coefficient due to an increase in electron concentration. For 0.2 ≤ x ≤ 0.3, the substituted Si4 + lowers the electrical conductivity. This is mainly attributed to decreases in the density and grain size as well as to the formation of secondary phases, such as Mn3O4, Mn2O3, and Sr2SiO4, resulting in a decrease in electron mobility. The substituted Si4 + reduces the thermal conductivity due to increased phonon scattering. The maximum dimensionless figure-of-merit (ZT) obtained in this study is 0.041 at 800 °C for x = 0.15. The partial substitution of Si4 + for Sr2 + in SrMnO3 − δ yields a significant improvement in the thermoelectric properties.

Graphical abstractTemperature dependence of the dimensionless figure-of-merit (ZT) for Sr1 − xSixMnO3 − δ (0.05 ≤ x ≤ 0.3) samples.Figure optionsDownload full-size imageDownload as PowerPoint slide