Study On AgCuTe Based Alloy Phase Diagram And Thermoelectric Properities

As a new type of clean energy materials,thermoelectric materials can realize the conversion between heat energy and electric energy,with owns the advantages of little volume,no noise,long life,and no pollution to the environment.It has broad application prospect and development space in aerospace exploration,reutilization of industrial waste heat,and solving the thermal problem of metal oxide semiconductor chips.In recent years,fast ion conductor material M₂X(M=Ag or Cu,X=S,Se or Te)has attracted wide attention due to its excellent thermoelectric properties.In principle,tellurides are heavier and less electronegative than sulfide and selenides,and should be more promising materials than sulfide and selenides.However,the thermoelectric performance is easily affected by the phase and microstructure,and the reports on the phase relationship of related systems are not perfect.Therefore,the further improvement of the thermoelectric performance can only be achieved by fully understanding the phase equilibrium and thermodynamic properties of Cu-Te,Ag-Cu-Te and other systems.In this paper,The Cu-Te system has been investigated by experiments and thermodynamics.The solubility of Te in Cu is 0?0.1 at.%.The Cu₂Te experienced five solid-state transitions which took place at 181.5,298.4,353.6,600.8 and 878.4 ? on the Cu-rich side,and were ascribed to?–?,?–?,?–?,?–?and?–?transformations.Based on the experimental data,the thermodynamic optimization of Cu-Te system was carried out,and a set of self-consistent thermodynamic parameters were derived.Based on the study of Cu-Te ternary system,the composition of Ag-Cu-Te ternary system was designed by extrapolation method,and the solidification of Ag-Cu-Te ternary system was studied experimentally a ternary eutectic reaction and a peritectic eutectic reaction were found.The Cu₂Te alloys prepared by improved heat treatment process have higher conductivity,lower thermal conductivity and highest z T value of 1.34(723K)than those prepared by traditional SPS sintering process.The x%Ag₂Te+(1-x%)Cu₂Te(x=0?15?30?45?60 and 90)alloys were designed according to the phase diagram.The results show that 15%Ag₂Te+85%Cu₂Te has lower thermal conductivity and better thermoelectric properties than Cu₂Te.The maximum z T of 15%Ag₂Te+85%Cu₂Te is 1.51 at 523K.The thermoelectric properties of the homogenized sample with copper-rich tip in the medium and high temperature region were better than those of the sample before annealing.