High temperature thermoelectric properties of the tetradymite Bi2− x Pb x Te2Se (0 ≤ x ≤ 0.03)

We report on the synthesis, characterizations, and high-temperature thermoelectric properties of polycrystalline samples of Bi2−xPbxTe2Se for 0 ≤ x ≤ 0.03. Powder x-ray diffraction and scanning electron microscopy confirm the successful insertion of Pb into the hexagonal unit cell of the tetradymite Bi2Te2Se. Pb acts as an acceptor-like impurity, gradually shifting the lightly doped, n-type electronic properties of Bi2Te2Se toward heavily doped, p-type properties in Pb-containing samples, which is additionally confirmed by electronic structure calculations. The increased degenerate character results in high power factors while maintaining low thermal conductivity values. This favorable combination of thermoelectric properties yields a peak dimensionless figure of merit ZT of 0.70 at 425 K for x = 0.02 in the direction perpendicular to the pressing direction.