High-temperature thermoelectric properties of n -type PbSe doped with Ga, In, and Pb

We report a systematic study of the thermoelectric properties of PbSe doped with Ga, In, and excess Pb as a function of carrier density and temperature. All metal dopants efficiently generate electron carriers in the crystal lattice with densities as high as {approx}10{sup 20} cm{sup -3} measured by the Hall effect. The Seebeck coefficient as a function of carrier density at room temperature was found to be similar for all dopants, while at 700 K substantial differences were observed with PbSe-In exhibiting a larger response. Infrared spectral reflectivity measurements at room temperature showed that both Ga and In substitution in PbSe weakens the curvature of the dispersion relation of the conduction band compared to Pb. This electronic effect contributes a larger density of states in transport processes at high temperatures. We have obtained thermoelectric figures of merit of {approx}0.9 at 900 K, exceeding that of PbTe for T>800 K.