Preparation And Performance Optimization Of Cu₃SbSe₄-based Thermoelectric Materials

Environmental pollution and energy shortage are two major issues in our society.Thermoelectric material is a kind of functional material which can realize the conversion between electric energy and thermal energy through the transport of carriers and phonons.Thermoelectric technology has shown great application prospects in many fields such as energy saving and environmental protection.So,researchers all over the world have paid more and more attention to it,and also the thermoelectric material properties have been continuously improved.However,most of the high-performance thermoelectric materials have more or less shortcomings,such as precious or toxic elements,high preparation requirements,which restrict their large-scale commercial application.Therefore,it is of great significance to study the abundant and non-toxic thermoelectric materials.In this paper,cheap and lead-free Cu₃SbSe₄-based thermoelectric material is taken as the research object,its electrical and thermal transport are regulated by different means,and its thermoelectric properties are also improved.The main research contents are as follows:1.The effect of Ag doping on the thermoelectric properties of Cu₃SbSe₄ was studied.Ag doping could effectively enhance the carrier concentration and effective mass of Cu₃SbSe₄,thus optimizing both electrical resistivity and Seebeck coefficient.The second phase AgSbSe₂was formed when the doping concentration x?0.05.Via Ag doping,a large number of point defects were introduced,which could block phonon transport,and reduce the lattice thermal conductivity.Finally,the Cu_2.85Ag_0.15SbSe₄ sample obtained a ZT value of 0.90 at 623K.2.The thermoelectric properties of Cu₃SbSe₄+x?AgSnSe₂?system was studied.It was found that AgSnSe₂ alloy could effectively enhance the carrier concentration of Cu₃SbSe₄ and optimize the electrical properties.At the same time,the point defects caused by the substitution of heterogeneous elements and the multiscale grain size distribution increased the scattering of phonons and decreased the lattice thermal conductivity.However,the total thermal conductivity had not been optimized due to the increase of the contribution of electronic thermal conductivity.Benefit from the great improvement of electrical properties,?Cu₃SbSe₄?_0.99?AgSnSe₂?_0.01.01 sample obtained the best ZT value of 1.01 at 673K.3.The effect of Ni/Sn co-doping on the thermoelectric properties of Cu₃SbSe₄ was studied.It was found that Ni/Sn co-doping could effectively enhance the carrier concentration of Cu₃SbSe₄ and optimize the electrical resistivity.However,the change of Ni doping had little effect on the electrical resistivity and Seebeck coefficient,so the enhancement of power factor was limited.At the same time,because the mass and radius between Ni atom and Cu atom were similar,it was not significant to reduce the thermal conductivity of Cu₃SbSe₄.Benefit from the improvement of electrical properties,the ZT value of all Cu_3-xNi_x Sb_0.99Sn_0.01Se₄?x=0.01,0.02,0.03?samples reached about 0.78 at 673K.