Thermoelectric properties of Lu-doped n-type LuxBi2-xTe2.7Se0.3 alloys

Lutetium-doped LuxBi2-xTe2.7Se0.3 (x = 0-0.3) nanopowders were synthesized by the hydrothermal method, and then they were hot-pressed into bulk pellets at 773 K under a pressure of 60 MPa in vacuum. The doping effects of Lutetium on the thermoelectric properties were investigated. Compared with the undoped sample, the electrical resistivities of Lu doped samples increased, and the Seebeck coefficients increased slightly. The lower carrier mobility caused by scattering may be the reason for the increase of the electrical resistivities of the doped samples. The thermal conductivities were significantly reduced because the Lu doping introduces a number of point defects into the crystals, which can effectively enhance phonon scattering, and because smaller grain size caused by Lu doping can enhance interface scattering. As a result, all the Lu doped LuxBi2-xTe2.7Se0.3 samples show higher ZT values compared with the undoped samples, indicating that Lu doping is an efficacious way to improve the thermoelectric properties of the n-type Bi2Te2.7Se0.3 alloys.