Thermoelectric properties of Bi1.5Pb0.5Sr2−xLaxCo2Oy polycrystalline materials

Polycrystalline samples of Bi1.5Pb0.5Sr2−x La x Co2O y (x = 0.1, 0.2, 0.3) with a layered structure were prepared by solid-state reaction method. All samples are p-type semiconductors. The thermoelectric properties, namely, the electric resistivity (ρ), Seebeck coefficient (S), and power factor (S 2/ρ) of the samples are dependent on chemical composition. The values of ρ, S, and S 2/ρ increase with an increase in temperature for all samples. The substitution of Pb2+ for Bi3+ and La3+ for Sr2+ improves the thermoelectric properties of the Bi2Sr2Co2O y system owing to the simultaneous decrease of electric resistivity and increase of Seebeck coefficient. As a result, the optimal thermoelectric property has been obtained in Bi1.5Pb0.5Sr1.7La0.3Co2O y and the power factor can reach 2.1 × 10−4 W·m−1·K−2 at 998 K.