Preparation And Performance Optimization Of Cu₂Te Based The Rmoelectric Materials

Thermoelectric materials can convert heat and electric energy into each other and have important application prospects in waste heat power generation and green refrigeration.Copper-based thermoelectric materials have attracted much attention in the development of thermoelectric materials because of their high thermoelectric properties,wide source of raw materials and economic advantages.Copper chalcogenides(Cu₂S,Cu₂Se and Cu₂Te)are copper-based thermoelectric materials,like Ag_2-xM(M=Se,Te)and Ag Cr Se₂,they have low thermal conductivity and are an important class of thermoelectric materials.Cu₂Te is a kind of superionic conductor,and its movable copper ion is easy to migrate within the crystal lattice.It belongs to the class of"phonon liquid-electron crystal"material.However,the high carrier concentration of Cu₂Te leads to the low Seebeck coefficient and ZT value.Therefore,the control of copper ion migration and the optimization of carrier concentration are important means to improve its thermoelectric performance.In this paper,based on Cu₂Te materials,the solid phase method is used to combine the vacuum tube and the calcination method to prepare samples.The Ag,Fe ions and Te vacancies are used to adjust the copper ion migration,carrier concentration and thermal conductivity to increase the ZT value.First of all,to explore the elements of Ag doping effect on the performance of thermoelectric materials.Research shows that when the molar ratio of Ag,Cu and Te elements for:1:1:1,the Power factor of Ag Cu Te material is the largest,reaching?1.03 m Wm^-1K^-2at?573 K,the cycle stability of the electrical transport properties is good,its top ZT value is 0.62.Secondly,Fe element is doped in the Cu and Ag sites of Ag Cu Te respectively to obtain Ag Cu_1-xFe_xTe(x=0.02-0.1)and Ag_1-xFe_xTe(x=0.02-0.1).Fe doping is beneficial to optimize the carrier concentration and improve the Seebeck coefficient and Power factor.When x=0.03,the Power factor of Ag Cu_0.97Fe_0.03Te reached?1.15m Wm^-1K^-2,which was 11.6%higher than Ag Cu Te's Power factor,and the thermal conductivity decreased slightly,so that the ZT value of Ag Cu_0.97Fe_0.03Te increased to?0.82 at 573 K.Compared with the ZT values of the two groups of doped samples,the thermoelectric properties of Ag Cu_1-xFe_xTe(x=0.02-0.1)doped by Fe at the Cu site are better.Finally,Te vacancy is introduced on the basis of Ag Cu_0.97Fe_0.03Te to increase phonon scattering and reduce thermal conductivity to improve its thermoelectric performance.The results showed that although the Power factor of Ag Cu_1-xFe_xTe_y(x=0.03,y=0.98-0.9)decreased,the thermal conductivity of Ag Cu_0.97Fe_0.03Te_0.96was the lowest,which was?0.314 Wm^-1K^-1at?573 K.Therefore,the ZT value of Ag Cu_0.97Fe_0.03Te_0.96was as high as?1.17,which was significantly higher than Ag Cu Te and Ag Cu Te_0.97Fe_0.03Te,which proved that the comprehensive effect of Fe doping and Te vacancy on the improvement of its thermoelectric performance was significant.The optimal carrier concentration of the system is around 10²⁰cm^-3.