CuGaTe_2和CuInTe_2的电子和热电性质的第一性原理研究  

The first-principles study of electrical and thermoelectric properties of CuGaTe_2 and CuInTe_2

作　　者：薛丽[1] 任一鸣[1] 

机构地区：[1]湖北科技学院电子与信息工程学院,咸宁437000

出　　处：《物理学报》2016年第15期171-179,共9页Acta Physica Sinica

基　　金：湖北科技学院博士启动基金(批准号:BK1427);湖北省科技厅项目(批准号:2013CFB038);国家自然科学基金(批准号:11304105)资助的课题~~

摘　　要：热电材料是通过载流子作用实现热能和电能直接转换的功能材料,在能源、环境、国防等领域具有重要应用.如何提高材料的转换效率是目前热电材料研究的关键.最近发现,三元黄铜矿Ⅰ-Ⅲ-Ⅳ_2(Ⅰ=Ag,Cu;Ⅲ=Al,Ga,In;Ⅳ=S,Se,Te)是一类潜在的高性能热电材料,其结构独特,可通过多种途径优化其性能.本文采用基于密度泛函理论的第一性原理方法系统地研究CuGaTe_2和CuInTe_2的电子特性,为提高其热电效率提供新思路研究发现改进的Becke Johnson-广义梯度近似比广义梯度近似交换关联近似计算的能隙值更接近实验值.基于玻尔兹曼理论研究了体系热电性质,发现通过优化载流子的浓度可以改善体系的热电性.通过拟合计算的晶格热导率发现,在300-800 K,CuGaTe_2和CuInTe_2的晶格热导率和温度成反比,表明其晶格热导率主要来源于声子散射,并且声子散射又是以Umklapp散射为主.CuGaTe_2在700 K的热电优值ZT可以达到0.63,远大于其他Te类材料的ZT值.The thermoelectric material is a kind of new functional material,which can convert industrial waste heat and automobile exhaust into the available electric energy by the interaction of carriers.It is widely used in energy,environment,national defense and other fields.For the research of thermoelectric materials,it is the most important to improve the conversion efficiency now.Due to their unique structural properties,the ternary chalcopyrite semiconductors Ⅰ-Ⅲ-Ⅳ2（Ⅰ=Ag,Cu;Ⅲ=A1,Ga,In;Ⅳ=S,Se,Te） display the better thermoelectric performances at high temperature.Many studies show that there are many ways to improve their performances.In order to optimize their thermoelectric efficiencies the structural,elastic and thermoelectric properties of CuGaTe2 and CuInTe2 are studied by employing the density function theory and semi-classical Boltzmann transport theory within the constant time approximation.The electronic band structures are calculated using the Tran-Blaha modified Becke-Johnson potential（MBJ-GGA） and the generalized gradient approximation（GGA）.The calculated band gaps with MBJ-GGA of CuGaTe2 and CuInTe2 are 0.86 and 0.56 eV,which are more accurate than the calculated values with GGA.The shear modulus,and Young＇s modulus and sound velocities are determined from the obtained elastic constants.The constant-volume heat capacity is estimated based on the quasi-harmonic Debye model.The calculated temperature dependence of heat capacity agrees very well with the experimental result.Below room temperature,the heat capacity increases quickly with the increasing of temperature.Above room temperature,the heat capacity approaches to the Dulong-Petit limit.In paper,we assume that the lattice thermal conductivities of CuGaTe2 and CuInTe2 are mainly from the phonon scattering.And the phonon scattering is dominated by Umklapp scattering.The calculated lattice thermal conductivities can fit the form k1 = A/T — B in the temperature range of 300 800 K.For CuGaTe2,A = 2869.96 and B = 2.86.The fitting

关 键 词：黄铜矿半导体 热电材料 玻尔兹曼理论 第一性原理 

分 类 号：O469[理学—凝聚态物理]