Thermoelectric properties of bismuth-substituted calcium manganite Ca_1−xBi_xMnO_3−δ prepared via the electrostatic spray deposition method

Abstract

The thermoelectric properties of Ca_1−xBi_xMnO_3−δ sintered bodies prepared by the electrostatic spray deposition method and sintering technology were evaluated. Ca_0.95Bi_0.05MnO_3−δ showed the maximum power factor value of 230 µW·m⁻¹·K⁻² among Ca_1−xBi_xMnO_3−δ compounds at room temperature. From Seebeck coefficient, Hall coefficient and power generation efficiency measurements on CaMnO_3−δ and Ca_0.95Bi_0.05MnO_3−δ under high temperature, it was found that the power factor value of Ca_0.95Bi_0.05MnO_3−δ increased with temperature in the range of 300–873 K, and was 2 to 5 times higher than that of CaMnO_3−δ. The carrier concentration (n = 5.9 × 10²⁰ cm⁻³) of Ca_0.95Bi_0.05MnO_3−δ is two orders of magnitude higher than CaMnO_3−δ (n = 7.1 × 10¹⁸ cm⁻³) at 300 K. The increase in carrier concentration contributed to higher conductivity, power factor and power generation density in the Bi-substituted compound. In thermoelectric performance evaluations, the power density reached 625 mW·cm⁻² for Ca_0.95Bi_0.05MnO_3−δ with a temperature difference of 444 K, an 11-fold increase compared to the parent compound CaMnO_3−δ (57 mW·cm⁻²).