High-temperature Thermoelectric Properties of the Ca_1-xBi_xMnO₃ System

Polycrystalline samples of Ca_1-xBi_xMnO₃ (0.02 ≤ x ≤ 0.20) were studied by means of x-ray diffraction, electrical resistivity (ρ), thermoelectric power (S), and thermal conductivity (κ) at high temperature. Bi doping leads to the lattice parameters a, b, and c increasing. And the ρ and the absolute value of S decrease rapidly with Bi doping. The largest power factor, S²/ρ, is obtained in the x = 0.04 sample, which is 3.6×10⁻⁴ Wm⁻¹ K⁻² at 400 K. The figures of merit (Z = S²/ρκ) for this sample and 1.0×10⁻⁴ and 0.86 × 10⁻⁴ K⁻¹ at 600 and 1000 K, respectively.