The enhanced thermoelectric properties of BiMnO3 ceramics by Sr-doped

A series of Bi1-xSrxMnO3 (x = 0.40, 0.45, 0.50, 0.55) samples labeled as BSMO040, BSMO045, BSMO050, and BSMO055, respectively, have been fabricated by the modified solid-state reaction method. The crystal structural, microstructures, and chemical states of the elements and the thermoelectric properties were investigated with respect to the partial substitution of Sr2+ for Bi3+. The samples were characterized by x-ray diffraction (XRD) at 723 K, scanning electron microscopy (SEM), and x-ray photoelectron spectroscopy (XPS). Moreover, their electrical conductivities (sigma), Seebeck coefficients (S), and thermal conductivities (kappa) were determined. All the samples exhibited orthorhombic structure. The partial substitution of Sr2+ for Bi3+ caused valence shift of someMnions from +3 to +4 to maintain electric charge balance. The change in electric charge led to an increase in electron concentration, and thus, the electrical conductivity as well as the absolute value of Seebeck coefficient increased. Consequently, the power factor also increased. The highest power factor (0.3. x. 10(-4) Wm(-1) K-1) was obtained for BSMO055 at 1023 K. Moreover, the highest dimensionless figure-of-merit (ZT) obtained in this study was 0.015 for BSMO055 at 1073 K. It can be concluded that the partial substitution of Sr2+ for Bi3+ in the Bi1-xSrxMnO3 samples (x = 0.40, 0.45, 0.50, and 0.55) improved the thermoelectric properties effectively.