Thermoelectric Properties Of P-type Bi_xSb_2-xTe₃Solid Alloy And Sb_xGe_1-xTe

As a functional material, thermoelectric materials could directly convert heat to electricity, making them promising for wide applications. To promote thermoelectric materials in the market application, the thermoelectric properties should be further improved. Bi2Te3and its solid solution alloy is the best p-type thermoelectric material near the room temperature (RT)，and the GeTe-based materials are the classic ones during the medium temperature. In this paper we manage to improve thermoelectric properties by doping to optimize the carrier concentration. In this paper, fine grain dense p-type thermoelectric bulk samples with good crystallinity were obtained via high energy ball milling and hot-pressing methods.The peak ZT=1.3at325K is archived for Bi0.5Sb1.5Te3sample. It owns much higher ZT than the pure Bi2Te3, primarily due to the significant reduction in lattice thermal conductivity and improvement in power factor (S2σ). For the Sn-doped Bi0.5Sb1.5Te3samples, higher Seebeck coefficients and lower electric conductivity than pure Bi0.5Sb1.5Te3samples are archived since there is less vancancy and anti-site defects in the doped samples. For the AZO、TiO2、GeTe and Al doped Bi0.5Sb1.5Te3samples, increased vacancies、anti-site defects and heterogeneous interfaces caused by heterogeneous doping impurities lead to a much higher electric conductivity which counteract the reduced lattice thermal conductivity, the ZT values don’t get improved. How to reduce the carrier concentration in the heterogeneous doped samples become the major content in the next stage.For SbxGe1-xTe (x=0.1,0.3,0.4,0.5) samples, the peak ZT~1.73at727K were obtained by the component of Sb0.04Ge0.96Te. The Sb doping reduce the electric and thermal conductivity, which is benefited from the lower carrier concentration due to the reduced vacancy, and the distribution of a large number of micron grains and phase boundaries inside material which scattering phonon, respectively. The expansion stability of GeTe-based materials was improved significantly after the Si additthermal ion.