Structural Modulation And Performance Optimization Of Bi_0.4Sb_1.6Te₃ Thermoelectric Alloys By Doping And Composite

Thermoelectric materials as a new renewable energy material,has a wide application prospect in thermoelectric power generation and thermoelectric cooling.Among them,Bi₂Te₃ based alloys are currently the most excellent thermoelectric materials at room temperature,so further improvement in the performance of these materials becomes the focus of research.In this study using p-type Bi_0.4Sb_1.6Te₃ as the matrix,the effect of Ge element doping,GeTe solution and SiC compound on the microstructure and thermoelectric properties of the sample was systematically studied through the vacuum melting method combined with SPS sintering technology.The main results aer as follows:?1?The effects of different vacuum melting process systems?melting temperature and holding time?on the properties of the matrix were studied.The results showed that,the melting temperature of 950?and annealed at 525??A2 sample?obtain the highest PF of37.1?W cm^-1K^-2,and finally the maximum ZT value was 0.93 at 363K,which was the best melting process.?2?The Ge_xBi_0.4Sb_1.6Te₃ alloy prepared by melting method,Ge elements introduced increasing the conductivity by 11.5–36%,and decreasing the thermal conductivity by4–16%.As a result a maximum ZT value reaches 1.47 at 383K for Ge_0.07Bi_0.4Sb_1.6Te₃sample,which is 69%higher than that of the undoped sample.The results show that the SPS samples obtain dense blocks.The final Ge_0.05Bi_0.4Sb_1.6Te₃ samples reached a maximum ZT value of 1.16 at 363 K,which is 30%higher than undoped.Although the thermoelectric properties are slightly reduced after SPS,the mechanical properties are enhanced and the defects of easy cleavage of molten samples are compensated.?3?The GeTe/Bi_0.4Sb_1.6Te₃ alloy prepared by smelting combined with SPS greatly improves the conductivity and thus the power factor of the material,0.1wt%GeTe-Bi_0.4Sb_1.6Te₃ sample has a maximum power factor of 45?W cm^-1K^-2,which is 45%higher than that of the matrix;finally,the maximum value is 1.18 at 363 K and the average ZT of is 0.983.?4?The electrical conductivity is increased after the nanocomposite of the nano SiC,which makes the power factor of the nanocomposite sample improved.Meanwhile,the presence of the second phase of the nano reduces the lattice thermal conductivity,and the final 0.8 vol%SiC sample gets the highest ZT value of 1.04 at 343 K,which is 17%higher than that of the undoped sample.