本文選題：結(jié)構(gòu)　切入點(diǎn)：摻雜半導(dǎo)體　出處：《山東大學(xué)》2017年博士論文　論文類型：學(xué)位論文

【摘要】：含有磷族元素(第十五主族)的化合物,由于其數(shù)目繁多,表現(xiàn)出非常豐富的結(jié)構(gòu)類型和多樣的性質(zhì),引起了人們的廣泛研究。由于環(huán)境污染、能源短缺等現(xiàn)實(shí)問題的加劇,能將廢熱轉(zhuǎn)換成電能回收再利用的熱電材料逐漸受到人們的重視并得到不斷的發(fā)展。Zintl相化合物由于其復(fù)雜的晶體和電子結(jié)構(gòu),被認(rèn)為是極具潛力的熱電材料。本論文主要開展了 Zintl相中9-4-9體系和1-1-1體系結(jié)構(gòu)相關(guān)熱電材料的制備、結(jié)構(gòu)與性能優(yōu)化工作。1、Ca9Zn4+xSb9化合物合成及熱電性質(zhì)研究9-4-9體系中Ca9Zn4+xSb9結(jié)構(gòu)化合物,具有較大的單胞和復(fù)雜的晶體結(jié)構(gòu),從而具有較低的晶格熱導(dǎo)率,進(jìn)而展現(xiàn)出較好的熱電性質(zhì)。通過無機(jī)固相的方法,我們得到了 Ca9Zn4.5Sb9的純相,其ZT值大約在0.37左右。在測試中得知,較高的電阻率是阻礙其熱電性質(zhì)提升的主要原因,因此在之后的工作中,我們通過部分取代來提升材料的電學(xué)性能,從而得到更優(yōu)的熱電性質(zhì)。2、Ca9Zn4+xSb9合物間隙原子位置摻雜改性為了進(jìn)一步對Ca9Zn4+xSb9進(jìn)行進(jìn)行研究,我們選擇用Al代替部分的Zn原子,并得到了這幾種化合物的純相Ca9Zn4.5-xAl2x/3Sb9(x=0,0.5,1),然后對其熱電性質(zhì)進(jìn)行了研究。在該體系研究中發(fā)現(xiàn),通過用Al取代Zn原子,可以使間隙位置的缺陷濃度增加,體系的遷移率大幅下降,材料的導(dǎo)電性能明顯降低,不利于熱電性能的提升。通過實(shí)驗(yàn)與理論計(jì)算的分析,我們進(jìn)一步設(shè)計(jì)并得到了摻Cu的化合物Ca9Zn4.5-xCuxSb9(x=0.05,0.1,0.15,0.2),在保證間隙原子濃度的情況下,顯著提升了材料的電導(dǎo)率,并使得功率因子大幅度提高,最終優(yōu)化了熱電性能。在873K時,Ca9Zn4.35Cu0.15Sb9的熱電優(yōu)值達(dá)到了 0.72,是未摻雜前Ca9Zn4.5Sb9的兩倍。之后我們又選擇了原子半徑更大的Ag原子來進(jìn)行摻雜,得到了一系列化合物Ca9Zn4.5-xAgxSb9(x=0.05,0.1,0.15,0.2),并對其進(jìn)行了相應(yīng)熱電性質(zhì)的測試,最終也優(yōu)化了熱電性能。3、陽離子"尺寸效應(yīng)"對Ca9Zn4+xSb9化合物熱電性質(zhì)的影響為了繼續(xù)研究陽離子摻雜對Ca9Zn4+xSb9結(jié)構(gòu)化合物熱電性質(zhì)的影響,我們選擇用尺寸更大的Eu原子來取代部分Ca。在后續(xù)對其進(jìn)行的霍爾性能測試中發(fā)現(xiàn),載流子濃度隨著Eu摻雜濃度的增加略微減小,但是遷移率顯著增大的趨勢更加明顯。這也表明在陽離子位置摻雜半徑更大的Eu,有利于間隙原子位置"容納"更多的Zn原子,這點(diǎn)可以由摻雜后變大的晶胞參數(shù)來證實(shí),而間隙原子位置中更多的Zn,帶來了遷移率的明顯提高。在后續(xù)的電學(xué)性質(zhì)及熱學(xué)性質(zhì)的測試中,也得到了相符的變化規(guī)律。在測試的基礎(chǔ)上,通過對其有效質(zhì)量及洛倫茲常數(shù)等的計(jì)算,進(jìn)一步對其物理性質(zhì)進(jìn)行了研究。最終綜合考慮了材料的各種相關(guān)性質(zhì),獲得的Ca8.2Eu0.8Zn4.5Sb9熱電材料,在873K時具有較高的熱電優(yōu)值ZT～0.81。4、幾種新晶體的發(fā)現(xiàn)并對其熱電性質(zhì)進(jìn)行研究我們采用金屬助熔劑法通過在YbAgSb中摻雜稀土元素引入缺陷,得到了兩種新的晶體,并通過單晶衍射確定其結(jié)構(gòu)式為Yb1.76La0.24Ag1.79Sb2和Yb1.67Ce0.33Ag1.74Sb2。根據(jù)其元素比例,采用高溫熔煉爐的方法快速而又方便地制得了一系列新的化合物Yb0.85RE0.15Ag0.85Sb(RE=La,Ce,Pr,Nd,Sm),并對對其行了熱電性質(zhì)測試,Yb0.85Ce0.15Ag0.85Sb的ZT值在1023K時達(dá)到0.4。經(jīng)過分析得知,是由于該體系化合物的載流子濃度過高,所以為了降低p型摻雜半導(dǎo)體的載流子濃度,繼續(xù)在Yb的位置上摻入Ca,得到一系列新的化合物Yb0.85-xCaxCe0.15Ag0.85Sb(x=0.1,0.2,0.3,0.4,0.5,0.6),并提升了材料的熱電性能。
[Abstract]:Contains pnicogen (fifteenth main group) of the compound, due to its large number of exhibit structural type is very rich and diverse properties, have been widely researched. Due to environmental pollution, energy shortages and other problems intensified, waste heat can be converted into electrical energy thermoelectric materials recycling by people gradually attention to and the development of.Zintl phase compounds because of the crystal and electronic structure of the complex, is considered to be a potential thermoelectric material. This paper carried out the Zintl phase of 9-4-9 system and 1-1-1 system structure and thermoelectric material preparation, structure and performance optimization of.1, synthesis and thermoelectric properties of Ca9Zn4+xSb9 compounds with Ca9Zn4+xSb9 structure the 9-4-9 system has a large compound, single cell and complex crystal structure, which has a lower lattice thermal conductivity, and show good thermoelectric properties Through the method of inorganic solid matter. And we got the pure phase Ca9Zn4.5Sb9, the ZT value is about 0.37. In that test, high resistivity is the main reason to hinder its thermoelectric properties improve, so after work, we replace the electrical properties to enhance the material through the part, so as to get the.2 the thermoelectric properties better, Ca9Zn4+xSb9 complexes of Ca9Zn4+xSb9 were studied in order to change the position of interstitial doping, we choose to use Al instead of part of Zn atoms, and these compounds pure phase Ca9Zn4.5-xAl2x/ 3Sb9 (x=0,0.5,1), and then studied on the thermoelectric properties. Found in the system research. By replacing Zn atoms with Al, can increase the defect concentration gap position, system migration rate fell sharply, the electric conductivity of the materials is significantly reduced, is not conducive to the promotion. The thermoelectric properties Experimental analysis and theoretical calculation, we further design and obtained the Cu doped compound Ca9Zn4.5-xCuxSb9 (x=0.05,0.1,0.15,0.2), in order to ensure the interstitial concentration conditions, significantly improve the conductivity of the material, and the power factor is improved greatly, to optimize the thermoelectric properties. At 873K, ZT value reached 0.72 Ca9Zn4.35Cu0.15Sb9 that is two times larger than that of the undoped Ca9Zn4.5Sb9. Then we choose the atomic radius larger Ag atoms are doped, obtained a series of compounds Ca9Zn4.5-xAgxSb9 (x=0.05,0.1,0.15,0.2), and has carried on the corresponding thermal properties test, finally optimize the thermoelectric properties of.3. The effect of cationic "size effect" on thermoelectric properties Ca9Zn4+xSb9 compounds in order to continue to influence of cation doping on the structure of Ca9Zn4+xSb9 compound thermoelectric properties, we choose the larger size of the original Eu To replace Ca. Holzer found in the performance test for subsequent, the carrier concentration with the increase of Eu doping concentration decreased slightly, but significantly increased the migration rate trend is more obvious. It also shows that the larger cation sites in the radius of doped Eu, is conducive to the clearance of atomic positions "accommodating" more Zn atoms. This can be changed by doping after the cell parameters of the confirmed and interstitial position more Zn, brought increased mobility. The electrical properties and thermal properties of the follow-up tests, also obtained consistent. On the basis of test, through the calculation of the effective mass and Lorenz constant, further the physical properties were studied. Finally considering the various properties of materials, Ca8.2Eu0.8Zn4.5Sb9 thermoelectric materials obtained, ZT is high in 873K when the value of ZT to 0 .81.4, several new crystals were studied by us found in YbAgSb doped rare earth metal flux method by introducing defects on the thermoelectric properties, two new crystals were obtained, and the structural formula of Yb1.76La0.24Ag1.79Sb2 and Yb1.67Ce0.33Ag1.74Sb2. according to the proportion of elements by single crystal diffraction determined by method of high temperature smelting furnace and quickly got to form a series of new compounds Yb0.85RE0.15Ag0.85Sb (RE=La, Ce, Pr, Nd, Sm), and the line of the thermoelectric properties test, Yb0.85Ce0.15Ag0.85Sb ZT value reached 0.4. after analysis showed that in 1023K, is due to the high carrier concentration of compound system, so in order to reduce the carrier concentration of P type doped semiconductor to continue, the incorporation of Ca in the position of Yb, obtained a series of new compounds Yb0.85-xCaxCe0.15Ag0.85Sb (x= 0.1,0.2,0.3,0.4,0.5,0.6), and enhance the material. The thermoelectric properties of materials.

【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：TB34

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