Effects Of Element Doping And Nano-siC Dispersion On The Thermoelectric Properties Of Bi₂Sr?Ba?₂Co₂O_y

With the development of economy,the problem of energy crisis is becoming more and more serious.Thermoelectric conversion technology is a technology that can realize the direct conversion of thermal energy and electric energy.It is clean,pollution-free and convenient to use.The energy conversion efficiency of thermoelectric devices is closely related to the dimensionless constant ZT of materials.When the temperature is a constant,the larger ZT,the higher power generation efficiency.Therefore,the core of a thermoelectric material is to improve its ZT value.According to the definition formula of ZT?ZT=S²T/???,the ZT value is related to the conductivity,Seebeck coefficients and thermal conductivity of materials.Increasing the ZT value of materials needs to increase the power factor?PF=S²/??,and reduce the thermal conductivity of the thermoelectric materials.It is found that element doping and nano-second phase dispersion are two important ways to improve the thermoelectric properties of thermoelectric materials.Cobalt-based oxide thermoelectric materials Bi₂Sr₂Co₂O_y and Bi₂Ba₂Co₂O_y have better chemical and thermal stability than traditional alloy semiconductor thermoelectric materials.At the same time,they also exhibit excellent thermoelectric properties in high temperature field.In recent years,oxide thermoelectric materials have aroused a research upsurge among researchers.In this paper,all the samples were prepared by the traditional solid-state reaction method.The phase structure characterization showed that the prepared samples were pure phase.SiC nanoparticles as the nano-second phase of nanoparticles were added into Bi₂Sr₂Co₂O_y matrix.The power factor and thermal conductivity were measured and calculated.It was found that the addition of appropriate amount of SiC nanoparticles could increase the power factor and reduce the thermal conductivity.At923K,the maximum ZT value of Bi₂Sr₂Co₂O_y+0.05 wt%SiC could reach 0.24.In addition,appropriate SiC nanoparticles were added to Bi₂Sr₂Co₂O_y matrix doped with alkali metal group elements Na and K.The results show that the thermal and electrical properties of Bi₂Sr₂Co₂O_y are greatly improved due to the optimization of power factor and the dispersion of SiC nanoparticles.At 923K,the maximum ZT values of Bi_1.8Na_0.2Sr₂Co₂O_y+0.025wt%SiC and Bi_1.9K _0.1Sr₂Co₂O_y+0.05 wt%SiC are 0.26 and 0.25,respectively.Finally,the effects of Pb doping and SiC nanoparticles dispersion on the thermoelectric properties of Bi₂Sr₂Co₂O_y and Bi₂Ba₂Co₂O_y were studied.The results of measurement and calculation show that the doping of heavy metal Pb can effectively optimize the electrical transport properties of these two cobalt-based oxide thermoelectric materials.At 923K,the power factors of Bi_1.6Pb_0.4Sr₂Co₂O_y+0.05 wt%SiC and Bi_1.8Pb_0.2Ba₂Co₂O_y+0.1wt%SiC are increased by 39%and 31%,respectively.