Preparation And Thermoelectric Properties Of CuInTe₂ Based Thermoelectric Composites

Thermoelectric materials can realize the direct transformation between electric energy and thermal energy through the Seebeck effect.It is a kind of green energy material and provides a possibility for the rapid development of new energy.At present,high-performance thermoelectric materials have some disadvantages such as complex preparation process,poor mechanical properties or containing toxic elements.Diamond-like structure semiconductor CuInTe₂ is considered to be a thermoelectric material with excellent properties in the800K?900K temperature range because of its special crystal structure,low lattice thermal conductivity and good electrical transport properties.However,the preparation of CuInTe₂often takes a long annealing time,resulting in energy consumption.In this paper,the process route of microwave heating technology is developed in the preparation of thermoelectric materials,and the heterocomposite scheme is used to enhance the thermoelectric properties of CuInTe2.The main research contents are as follows:In order to reduce the energy consumption and time cost in the preparation process,CuInTe₂,Sn Te,Cu₂Se and Sn Se polycrystalline materials were synthesized by microwave heating technology.By changing the absorbing materials,the four high-purity polycrystalline materials can be synthesized rapidly in 10 minutes.The bulk materials were prepared by microwave synthesis-ball milling-rapid hot pressing sintering.The results showed that the thermoelectric properties of microwave synthesized materials were similar to those of traditional methods.The ZT values of CuInTe₂,Sn Te,Cu₂Se and Sn Se were 0.36,0.23,0.68and 0.35 at 700 K,respectively.Sn Te with high carrier concentration was selected as the composite phase to enhance the conductivity of CuInTe₂,and the effect of Sn Te/CuInTe₂ heterostructure on CuInTe₂thermoelectric material was analyzed.The x wt.%Sn Te/CuInTe₂(x=0.5,1.0,2.0,4.0)bulk composites were prepared by ball milling ultrasonic vibration mixing and rapid hot pressing sintering.Sn Te with cubic phase and tetragonal phase was uniformly dispersed in the matrix.Cu/Sn elements diffused and migrated to each other during sintering,and submicron pores and submicron particles existed in the microstructure.The addition of Sn Te can greatly enhance the electrical conductivity,but the Seebeck coefficient was greatly reduced,and the power factor was not improved.The lattice thermal conductivity of the material was effectively reduced.At675 K,the ZT value of 2 wt.%Sn Te/CuInTe₂ sample was 0.44,which was 42%higher than that of pure phase.The average ZT value of 300 K?700 K was 0.16,which was 33.3%higher than that of pure phase.The fast ionic conductor Cu₂Se with the properties of"phononic liquid electronic crystal"was selected as the composite phase,and the influence of Cu₂Se/CuInTe₂ heterostructure on CuInTe₂ thermoelectric materials was analyzed.The x wt.%Cu₂Se/CuInTe₂(x=0.5,1.0,2.0,4.0)bulk composites were prepared by ball milling ultrasonic vibration mixing and rapid hot pressing sintering.At room temperature,Cu₂Se was uniformly dispersed in the matrix with?structure.The results showed that the sintered bulk had high compactness,no pores and no obvious boundary between the two phases.Cu₂Se and CuInTe₂ were interlaced with each other to form a close heterogeneous interface.The addition of Cu₂Se improved the electrical conductivity and power factor of CuInTe₂ material.However,the thermal conductivity increased due to the addition of Cu₂Se.At 675 K,the ZT value of 1 wt.%Cu₂Se/CuInTe₂ sample was 0.41,which was 32%higher than that of pure phase.The average ZT value of 300 K?700K was 0.15,which was 25%higher than that of pure phase.Sn Se crystal with low lattice thermal conductivity was selected as the composite phase,and the effect of Sn Se/CuInTe₂ heterostructure on CuInTe₂ thermoelectric material was explored.x wt.%Sn Se/CuInTe₂(x=0.5,1.0,2.0,4.0)bulk composites were prepared by ball milling-ultrasonic vibration mixing and rapid hot pressing sintering.The materials had high density,no porous phase and obvious layered structure of Sn Se crystal.During the sintering process,Sn element diffused and migrated,and submicron Sn Se at the grain boundary reacted with CuInTe₂ and formed binary nano submicron particles.The electrical conductivity and power factor were enhanced when the composite content reached 2 wt.%,and the thermal conductivity was effectively reduced when the composite content reached 4 wt.%.At 700 K,the ZT value of 4 wt.%Sn Se/CuInTe₂ sample was 0.72,which was 100%higher than that of pure phase.The average ZT value of 300 K?700 K was 0.13.