Fabrication and thermoelectric properties of Sr1 − xSixMnO3 − δ.

The effect of Si 4 + content on the microstructure and thermoelectric properties of Sr 1 − x Si x MnO 3 − δ (0.05 ≤ x ≤ 0.3) samples is discussed. For x ≤ 0.15, the substitution of Si 4 + for Sr 2 + 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 Si 4 + 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 Mn 3 O 4 , Mn 2 O 3 , and Sr 2 SiO 4 , resulting in a decrease in electron mobility. The substituted Si 4 + 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 Si 4 + for Sr 2 + in SrMnO 3 − δ yields a significant improvement in the thermoelectric properties. [ABSTRACT FROM AUTHOR]