發(fā)布時間：2018-05-03 08:02

  本文選題：碲化鉍 + 摻雜��； 參考：《北京郵電大學(xué)》2015年碩士論文

【摘要】：熱電材料領(lǐng)域研究的重點在于提高熱電材料的轉(zhuǎn)換效率也就是熱電優(yōu)值。其中摻雜是提高材料熱電優(yōu)值的有效手段。基于Bi2Te3的熱電材料在室溫下有很好的熱電性能,ZT值能達(dá)到1左右,被廣泛的應(yīng)用于熱電工業(yè)領(lǐng)域。本論文主要基于密度泛函理論和半經(jīng)典的波爾茲曼輸運(yùn)理論,系統(tǒng)的研究了(Bi,Sb)2(Te,Se)3四元摻雜體系以及堿金屬元素Na摻雜Bi2Te3體系的電子結(jié)構(gòu)和熱電性質(zhì)。本文主要研究內(nèi)容如下： 1.研究了(Bi,Sb)2(Te,Se)3四元雙摻體系的幾何優(yōu)化和電子結(jié)構(gòu)性質(zhì)計算。我們采用1×1×3的超晶胞結(jié)構(gòu)作為我們的計算模型,以保證計算的準(zhǔn)確性。基于密度泛函理論和第一性原理的方法,我們計算了體系的能帶結(jié)構(gòu),總態(tài)密度以及分波態(tài)密度。并分析了模型不同原子施加自選軌道耦合作用對體系能帶結(jié)構(gòu)的影響。我們還研究了費米能級附近態(tài)密度與塞貝克系數(shù)之間的關(guān)系。 2.研究了四種(Bi,Sb)2(Te,Se)3摻雜結(jié)構(gòu)的熱電性質(zhì)。根據(jù)波爾茲曼輸運(yùn)理論以及弛豫時間近似方法,我們計算了體系的塞貝克系數(shù)、電導(dǎo)率、功率因子,并分析了不同摻雜位置對于體系熱電性質(zhì)的影響。由于Bi2Te3是一種典型的各向異性材料,我們計算和對比了體系在xx方向和zz方向上的熱電性質(zhì)。最后得出了四種(Bi,Sb)2(Te,Se)3雙摻模型在費米能級附近n型摻雜和p型摻雜的熱電優(yōu)值,可以通過實驗手段調(diào)節(jié)載流子的濃度得到最佳ZT值。 3.研究了Na元素?fù)诫sBi2Te3體系的電子結(jié)構(gòu)與熱電性質(zhì)。我們采用了2×2×2的超晶胞結(jié)構(gòu)作為我們的計算模型,并設(shè)計了6.25%的Na原子摻雜比例。分析了自旋軌道耦合作用對于體系電子結(jié)構(gòu)計算的必要性,分析了堿金屬的引入對于體系能帶結(jié)構(gòu)的影響。接著我們根據(jù)波爾茲曼輸運(yùn)理論,結(jié)合弛豫時間近似方法,計算了NaBi15Te24體系的熱電傳輸系數(shù),研究了摻雜Na原子對于NaBi15Te24體系熱電性質(zhì)的影響。
[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.
【學(xué)位授予單位】：北京郵電大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TB34

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本文編號：1837671