•N-type LuxBi2-xTe2.7Se0.3 (x = 0–0.3) were prepared by hydrothermal method followed by hot pressing.•Lu-doping effects on the structure and thermoelectric properties of Bi2Te2.7Se0.3 were investigated.•The highest ZT value of Lu0.1Bi1.9Te2.7Se0.3 reaches 1.37 at 373 K.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.

The influence of Ba doping on the thermoelectric properties of Bi2−xBaxSr2 Co2Oy (x = 0.00, 0.025, 0.05, 0.075, 0.10, 0.125, and 0.15) samples prepared by the solid-state reaction method was investigated from 333 K to 973 K. For the samples with x ≤ 0.075, the electrical resistivity decreased with increase of the Ba doping amount due to p-type doping and they exhibited metallic electrical conductivity behavior, whereas the samples with x ≥ 0.10 exhibited semiconductor-like electrical conductivity behavior. The Seebeck coefficients of all the samples decreased with increase of the Ba doping amount. The thermal conductivity first decreased for x ≤ 0.075, then increased with higher Ba doping amounts. As an overall result, the dimensionless figure of merit (ZT) of Bi1.925Ba0.075Sr2Co2Oy reached the maximum value of 0.245 at 973 K, being 41% higher than that of the undoped sample.