Preparation And Thermoelectric Properties Of AgInTe₂ Based Compounds

As a kind of new energy material,thermoelectric material is environmentally friendly and can convert heat to electricity directly,attracting much attention.But relatively low thermoelectric conversion efficiency limits its large-scale commercial applications.AgInTe₂ based thermoelectric materials have low thermal conductivity and high Seebeck coefficient,therefore have potential applications for thermoelectric.So far,there are few reports about the thermoelectric performance of AgInTe₂.Compared with conventional thermoelectric materials,the electrical conductivity of AgInTe₂ is very low.The thermoelectric properties of AgInTe₂ based compound can be effectively optimized by improving electrical conductivity.From the foregoing,the main way to optimize the thermoelectric properties of AgInTe₂ material is to improve the electrical conductivity.In this paper,AgInTe₂compound was synthesized through melt-annealing combined with Plasma activated sintering.Then we studied the influence of the deficiency of Ag?In and Ga?Cu solid solution on its phase composition,microstructure,electrical transmission and thermal transfer performance.Finally,the influences of Te excess on the thermoelectric properties were studied.On the basis of Te excess,we also studied the solid solution of Ga in In site,and further optimized the thermoelectric properties of the material.The results show that:AgInTe₂ compound is a p-type thermoelectric material,with low electrical conductivity,higher Seebeck coefficient and low thermal conductivity.The maximum ZT value was 0.30 at 773 K.the deficiency of Ag and Ga can effectively increase the vacancy concentration and electrical conductivity of AgInTe₂ compound.When the deficiency of Ag was 0.05,the electrical conductivity was 412 S/m at 773 K,increased by 32%compared with intrinsic AgInTe₂ compound.Finally,Ag_0.99InTe₂and AgIn_0.99Te₂ have the best performance,of which the maximum ZT values were0.30 and 0.32 at 773 K respectively.The performance was improved slightly compared with intrinsic AgInTe₂ compound.For AgIn_1-xGa_xTe₂ compounds of Ga solid solution,the solid solution of Ga in In site enhanced the covalency and vacancy mobility,so the electrical conductivity significantly increased.AgIn_0.2Ga_0.8Te₂ sample has the best performance with maximum ZT value as 0.60 at 773 K,which is two times that of the value of intrinsic AgInTe₂ compound.For Ag_1-xCu_xInTe₂ compounds of Cu solid solution,the solid solution of Cu in Ag site increased the vacancies concentration and mobility,thus greatly improved the electrical conductivity.But its thermal conductivity also increased.Finally Ag_0.4Cu_0.6InTe₂ has the best performance with maximum ZT value as 1.0 at 773 K,which is increased by 235%compared with the intrinsic AgInTe₂sample.The excess of Te can improve hole concentration and electrical conductivity of AgInTe₂ compound,and at high temperature the change of thermal conductivity was not large,thereby the thermoelectric properties of the material was improved.Sample with Te excess?x=0.07?has the best performance with the maximum ZT up to 0.34,which is increased by 13%compared with intrinsic AgInTe₂ compound.On this basis,the influence of Ga solid solution on thermoelectric properties of AgIn_1-xGa_xTe_2.07compounds was researched.Finally,AgIn_0.2Ga_0.8Te_2.07.07 has the best performance with the maximum ZT value up to 0.65 at 773 K,which is increased by 117%compared with intrinsic AgInTe₂ compound.