Thermoelectric properties of Bi, Nb co-substituted CaMnO 3 at high temperature

Abstract

Ca 1− x Bi x Mn 1− y Nb yO 3 (0 ≤ x = y ≤ 0.1) was prepared using a conventional solid-state reaction method. The microstructures and homogeneity were confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD), and its high temperature thermoelectric properties were also characterized. The lattice parameter of orthorhombic perovskite increased with additional amounts of Bi and Nb. The electrical conductivity ( σ) increased, and Seebeck coefficient ( α) decreased, as the amount of Bi and Nb increased up to x = y = 0.08. The electrical conductivity decreased as the temperature increased, indicating metallic behavior, and the Seebeck coefficient increased with increasing temperature. As a result, thermoelectric properties were improved by substituting Bi and Nb into CaMnO 3. It showed maximum values at x = y = 0.04, in which the power factor (PF) was 200 μW/m K 2 and dimensionless figure of merit ( ZT) was approximately 0.1 at 873 K. The thermoelectric properties of Ca 0.96Bi 0.04Mn 0.96 Nb 0.04O 3 were improved nearly twofold over un-doped CaMnO 3.