Study of the Thermoelectric Properties of Lead Selenide Doped with Boron, Gallium, Indium, or Thallium

Group IIIA elements (B, Ga, In, and Tl) have been doped into PbSe for enhancement of thermoelectric properties. The electrical conductivity, Seebeck coefficient, and thermal conductivity were systematically studied. Room-temperature Hall measurements showed an effective increase in the electron concentration upon both Ga and In doping and the hole concentration upon Tl doping to similar to 7 x 10(19) cm(-3). No resonant doping phenomenon was observed when PbSe was doped with B, Ga, or In. The highest room-temperature power factor x 10(-3)W m(-1) K-2 was obtained for PbSe doped with 2 atom % B. However, the power factor in B-doped samples decreased with increasing temperature, opposite to the trend for the other dopants. A figure of merit (ZT) of similar to 1.2 at similar to 873 K was achieved in PbSe doped with 0.5 atom % Ga or In. With Tl doping, modification of the band structure around the Fermi level helped to increase the Seebeck coefficient, and the lattice thermal conductivity decreased, probably as a result of effective phonon scattering by both the heavy Tl3+ ions and the increased grain boundary density after ball milling. The highest p-type ZT value was similar to 1.0 at similar to 723 K.