Effects of Sn Doping on Thermoelectric Properties of p Type BiSbTe Alloy

A series of Sn-doped (Bi_0.5Sb_1.5)_1-xSn_xTe₃ (x=0, 0.25%, 0.5%, 1%) bulk samples were prepared by nano powders from high-energy ball milling and compacted samples from direct current pressing method.Then the phase, microstructure and thermoelectric properties of the samples were analyzed.The X-ray diffraction patterns showed that there was no other phases except Bi_0.5Sb_1.5Te₃ in all bulk samples, while the Scanning Electron Microscope images indicated that Sn doped samples had little effect on the grain size, resulting little change in lattice thermal conductivity.The Sn doped samples got higher Seebeck coefficient and lower electrical conductivity, which was mainly because of the influences on the carrier density from Sn dopant.The maximum dimensionless figure of merit ZT of 1.16 was archived at 348 K in Bi_0.5Sb_1.5Te₃ sample, which was mainly attributed to the reduced lattice thermal conductivity from the enhanced phonon scattering by the interfaces of greatly increased micron or sub-micron grains and precipitation than the sample prepared by conventional method.The prepared Bi_0.5Sb_1.5Te₃ sample's ZT is higher than 1 before 423 K, about 20% improving comparing with the average ZT of the sample prepared by traditional method, which is advantageous for practical application.