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Cu2Se has been considered as a promising thermoelectric material due to its unique structure and excellent performance. Herein, a series of Cu2-xNaxSe (x = 0, 0.01, 0.02, 0.03, and 0.04) polycrystalline samples were synthesized by combining hydrothermal synthesis and hot pressing to investigate the effects of Na-doping on the microstructure and thermoelectric properties of Cu2Se. Compared with the pristine Cu2Se, the Na-doping introduces numerous micro-pores that can optimize the thermal transport performance by strong phonon scattering effects of interfaces between the micro-pores and grains. The doped samples have excellent electrical properties and low thermal conductivity. The maximum value of ZT = 2.1 is obtained at 973 K for the Cu1.96Na0.04Se sample with nominal composition. The results confirm that introducing Na into Cu2Se is an effective and convenient strategy to improve the thermoelectric performance of the Cu2Se alloy by decreasing the lattice thermal conductivity. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]