Enhancement of thermoelectric performance of Cu 1.98 Se by Pb doping

Non-stoichiometric Cu2−xSe is considered as a potential “phonon liquid electronic crystal” thermoelectric material. Cu1.98Se has higher thermal conductivity than Cu2Se, but the power factor of Cu1.98Se is about twice that of Cu2Se. Its thermal conductivity could be further depressed by optimizing its thermal transport performance. In this work, lead-doped Cu1.98−xPbx/2Se (x = 0–0.03) nanopowders were synthesized using a hydrothermal method, and hot-pressed into bulk pellets to assess the effects of Pb doping on the thermoelectric properties of Cu1.98Se. The electrical resistivity and the Seebeck coefficients were increased by Pb doping. Ionization impurity scattering, together with decrease of hole concentration, appeared to decrease the electrical transport performance. The point defects and reduced carrier concentration together result in low thermal conductivity and lead to a high dimensionless figure of merit (ZT) value of 1.52 at 973 K for the nominal component Cu1.95Pb0.015Se sample.