Microstructure And Thermoelectric Properties Of A_xBi_0.5Sb_1.5-xTe₃?A=Yb?Mn?

Bismuth telluride material is the best performance of the room temperature thermoelectric materials,its ZT has reached the initial level of application,a lot of refrigeration devices has been successfully developed,such as ice cream machine,car small refrigerator.However,the bismuth telluride material appears to have a severe intrinsic excitation at higher than room temperature,resulting in a sharp decrease in the Seebeck coefficient,a rapid increase in thermal conductivity,so there will be a significant decrease in the ZT value.It restrict the electrical application at 100 to 300°C.In this paper,A_xBi_0.5Sb_1.5-xTe₃?A = Yb,Mn?was prepared by the combination of melting + ball milling and hot-pressing sintering.X-ray diffraction?XRD?,scanning electron microscopy?SEM?,conductivity / seebeck coefficient test system are used to detect the effects of two kinds of doping elements on the microstructure and thermoelectric transport properties of Bi_0.5Sb_1.5Te₃.It was found that the doping of Yb or Mn did not change the crystal structure and grain size of Bi_0.5Sb_1.5Te₃.The incorporation of Yb and Mn will increase the formation of inversion defects in the system and improve the Te vacancy concentration.With the increase of Yb doping amount,the lattice constant increases first and then decreases.With the increase of Mn content,the lattice constant shows a decreasing trend.Yb or Mn increase the bandgap and carrier concentration,pushing the temperature of intrinsic excitation to a higher temperature.Yb or Mn doping balances the conductivity and Seebeck coefficient of Bi_0.5Sb_1.5Te₃,and then improve the powerfactor.At the same time,the lattice thermal conductivity and bipolar effect induced by intrinsic excitation are reduced??L + ?bi?.Finally,the ZT values of the whole measured temperature range are increased,and the maximum value of ZT is increased to high temperature.For example,the maximum value of ZT of Yb0.01Bi0.5Sb1.49Te3 reaches 1.1,at 100 ?.The highest value of ZT of Mn0.005Bi0.5Sb1.495Te3 reached 1.3 at 150??Bi0.5Sb1.49Te3 room temperature ZT highest value was 1.0?.