碱金属掺杂碲化铋的电子结构及热电性质

发布时间：2018-05-03 08:02

本文选题：碲化铋 + 掺杂　；参考：《北京邮电大学》2015年硕士论文

【摘要】：热电材料领域研究的重点在于提高热电材料的转换效率也就是热电优值。其中掺杂是提高材料热电优值的有效手段。基于Bi2Te3的热电材料在室温下有很好的热电性能,ZT值能达到1左右,被广泛的应用于热电工业领域。本论文主要基于密度泛函理论和半经典的波尔兹曼输运理论,系统的研究了(Bi,Sb)2(Te,Se)3四元掺杂体系以及碱金属元素Na掺杂Bi2Te3体系的电子结构和热电性质。本文主要研究内容如下： 1.研究了(Bi,Sb)2(Te,Se)3四元双掺体系的几何优化和电子结构性质计算。我们采用1×1×3的超晶胞结构作为我们的计算模型,以保证计算的准确性。基于密度泛函理论和第一性原理的方法,我们计算了体系的能带结构,总态密度以及分波态密度。并分析了模型不同原子施加自选轨道耦合作用对体系能带结构的影响。我们还研究了费米能级附近态密度与塞贝克系数之间的关系。 2.研究了四种(Bi,Sb)2(Te,Se)3掺杂结构的热电性质。根据波尔兹曼输运理论以及弛豫时间近似方法,我们计算了体系的塞贝克系数、电导率、功率因子,并分析了不同掺杂位置对于体系热电性质的影响。由于Bi2Te3是一种典型的各向异性材料,我们计算和对比了体系在xx方向和zz方向上的热电性质。最后得出了四种(Bi,Sb)2(Te,Se)3双掺模型在费米能级附近n型掺杂和p型掺杂的热电优值,可以通过实验手段调节载流子的浓度得到最佳ZT值。 3.研究了Na元素掺杂Bi2Te3体系的电子结构与热电性质。我们采用了2×2×2的超晶胞结构作为我们的计算模型,并设计了6.25%的Na原子掺杂比例。分析了自旋轨道耦合作用对于体系电子结构计算的必要性,分析了碱金属的引入对于体系能带结构的影响。接着我们根据波尔兹曼输运理论,结合弛豫时间近似方法,计算了NaBi15Te24体系的热电传输系数,研究了掺杂Na原子对于NaBi15Te24体系热电性质的影响。
[Abstract]:The emphasis of thermoelectric materials research is to improve the conversion efficiency of thermoelectric materials, that is, thermoelectric excellence. Doping is an effective means to improve the thermoelectric value of materials. The thermoelectric materials based on Bi2Te3 have good thermoelectric properties and the value of ZT can reach about 1 at room temperature, so they are widely used in the field of thermoelectric industry. Based on the density functional theory (DFT) and the semi-classical Boltzmann transport theory, the electronic structure and thermoelectric properties of the quaternary doping system and Na doped Bi2Te3 system are systematically studied in this paper. The main contents of this paper are as follows: 1. The geometric optimization and the calculation of electronic structure properties of Bi-SbSb2TeSe 3 quaternary double doped system have been studied in this paper. The supercell structure of 1 脳 1 脳 3 is used as our computational model to ensure the accuracy of the calculation. Based on the density functional theory and the first-principle method, we calculate the energy band structure, the total density of states and the density of fractional state of the system. The influence of different atoms on the band structure of the system is analyzed. The relationship between the density of states near the Fermi energy level and the Seebeck coefficient is also studied. 2. The thermoelectric properties of four kinds of Bi-SbC2TE-SE3 doped structures have been studied. Based on the Boltzmann transport theory and the relaxation time approximation method, the Seebeck coefficient, conductivity and power factor of the system are calculated, and the influence of different doping positions on the thermoelectric properties of the system is analyzed. As Bi2Te3 is a typical anisotropic material, the thermoelectric properties of the system in xx direction and ZZ direction are calculated and compared. Finally, the thermoelectric excellence values of n and p type doping in the vicinity of Fermi level are obtained by four kinds of BiSbP2Te Te Se 3 double doped models. The best ZT value can be obtained by adjusting the carrier concentration by experimental means. 3. The electronic structure and thermoelectric properties of Na doped Bi2Te3 system were studied. The supercell structure of 2 脳 2 脳 2 is used as our computational model, and a 6.25% Na doping ratio is designed. The necessity of spin-orbit coupling to the calculation of the electronic structure of the system and the influence of the introduction of alkali metals on the band structure of the system are analyzed. Then, based on the Boltzmann transport theory and the relaxation time approximation method, we calculate the thermoelectric transport coefficients of NaBi15Te24 system and study the influence of doped Na atoms on the thermoelectric properties of NaBi15Te24 system.
【学位授予单位】：北京邮电大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB34

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