Thermoelectrical properties of lutetium-doped Bi₂Te₃ bulk samples prepared from flower-like nanopowders

Highlights: • Lu-doped Bi₂Te₃ flower-like nanopowders were synthesized using hydrothermal method. • Optimal Lu-doped samples can have a higher power factor than the undoped sample. • Figure of merit (ZT) for the Lu_0.1Bi_1.9Te₃ sample can reach 1.7 at 373 K. - Abstract: Lutetium-doped Bi₂Te₃ flower-like nanopowders were synthesized by hydrothermal method. The flower-like nanopowders were hot pressed into bulk pellets and the doping effects of lutetium on the thermoelectrical properties were investigated. The results show that the doping of lutetium can reduce the electrical resistivity greatly, while does not reduce the Seebeck coefficient too much, therefore results in a high power factor. Because the mass of the lutetium atom is close to the mass of the bismuth atom, replacing bismuth by lutetium will not increase the frequency of phonons greatly, which is helpful to remain a lower thermal conductivity. As a result of the combining effect of the lutetium doping and nanostructure of the sample, figure of merit (ZT) for the Lu_0.1Bi_1.9Te₃ sample can reach a high value 1.7 at 373 K