Theoretical Properties Of Tin Telluride-based Thermoelectric Materials

The prominent environmental problems,increasingly tight energy reserves,and increasing energy demand have caused thermoelectric materials to receive more and more attention.The thermoelectric conversion efficiency of thermoelectric materials is reflected by the thermoelectric figure of merit ZT.The higher the thermoelectric figure of merit ZT,the higher the thermoelectric conversion efficiency of the material,and the better the thermoelectric performance of the material.It can be said that improving the thermoelectric figure of merit is the direction of the joint efforts of all researchers in the field of thermoelectric materials.Pb Te-based thermoelectric materials have been favored by a large number of researchers due to their excellent thermoelectric properties,but for a long time,the performance of Pb Te-based materials has not been significantly improved.Based on the above situation,this paper studies the crystal structure,electronic structure and electron transport properties of Pb Te and Sn Te crystals and their superlattice structures Pb Te(110)-Eu Te(110)and Sn Te(110)-Eu Te(110)(Including Seebeck coefficient,electrical conductivity,power factor),and using Sn O₂ to explain the influence of various transport properties of thermoelectric materials on the thermoelectric properties of materials.First of all,this work calculates the structural parameters,electronic band structure and electronic density of states of Pb Te crystal and its superlattice structure Pb Te(110)-Eu Te(110)by means of exchange correlation functionals.The energy band diagram of Pb Te shows that both the conduction band and the valence band have energy band degenerates,and the N-type and P-type regions have sharper peaks than taught in the density of states diagram,indicating that the material is an N-type semiconductor thermoelectric material and P-type semiconductor thermoelectric materials are ideal.After constructing the superlattice structure Pb Te(110)-Eu Te(110),the Seebeck coefficient of the material is significantly improved compared with Pb Te material at a specific carrier concentration.In addition,the effective conductance mass mc can better reflect the Seebeck coefficient of this type of material,and can provide a reference for the study of the Seebeck coefficient of this type of material.The calculation process of Sn Te crystal and its superlattice structure Sn Te(110)-Eu Te(110)is similar to that of Pb Te.Also in the energy band diagram,it is shown that Sn Te has almost equivalent energy band degeneration at the bottom of the conduction band and the top of the valence band,indicating that Sn Te can be used as a good P-type semiconductor thermoelectric material as well as a good N-type semiconductor thermoelectric material This can also be confirmed from the density of states diagram.Through the calculation of electrical transport properties,it is found that the Sn Te superlattice Sn Te(110)-Eu Te(110)is better than Sn Te crystal in various thermoelectric parameters,indicating that the superlattice structure can effectively improve the thermoelectric performance of Sn Te.In the part of Sn O₂,through the combination of experimental data and the analysis of the energy band diagram,it is found that the Fermi level will migrate upwards as the doping concentration increases.The electrons at the bottom of the conduction band are higher than the conduction band because the Fermi level is higher.With the bottom,it is as high as 0.59 e V,so that the electrons doped with Sb element become conductive electrons,making Sn O₂ have the characteristics of metal.At the same time,the calculation data of the relaxation time in this paper shows that high temperature and low carrier concentration are also beneficial to increase grain boundary scattering,which also leads to higher mobility and conductivity.The above phenomena have enhanced the thermoelectric properties of Sn O₂ materials.