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运用传统固相法合成了Re掺杂的Mo3-x Re x Sb7(x=0,0.05,0.10)系列化合物,并通过热压烧结得到了致密样品。采用X射线粉末衍射(XRD)和X射线能量色散谱(EDS)表征了样品的相成分,同时经过第一性原理计算分析了Re掺杂对Mo3Sb7能带结构的影响,进而研究了Re掺杂对Mo3Sb7热电性能影响的规律。结果表明:当掺杂量x≤0.1时,Re均匀地掺杂于晶格中形成固溶体且所有样品均无第二相杂质生成,同时晶胞参数随着Re掺杂量的增长而减小。Mo3Sb7作为一种P型三维导电材料,当每化学单位的Mo3Sb7额外获得两个化学单位的价电子将由金属转变为半导体。在Re掺杂后Mo3Sb7费米面上移,这是因为Re比Mo多一个价电子,但由于固溶度的限制,Re掺杂并不能使其转化为半导体,且Re掺杂对于费米面处能带形状以及禁带宽度的影响也非常有限。由于Re较多的价电子,因此Re的引入降低了化合物Mo3Sb7的电导率,并提高了其热电势值,而电导率的降低也必然会减小载流子贡献的热导率,同时Re掺杂增加了晶格无序也降低了其晶格热导率,因此Mo3Sb7总的热导率得到了降低,最后其热电性能得到了提高。其中,经过Re掺杂后的化合物Mo2.90Re0.10Sb7在860 K下ZT值达到0.127,比化合物Mo3Sb7提高了23.3%。
The Re-doped Mo3-x Re x Sb7 (x = 0,0.05,0.10) series compounds were synthesized by the conventional solid-state method and the compact samples were obtained by hot pressing. The phase composition of the samples was characterized by X-ray powder diffraction (XRD) and energy dispersive X-ray spectrometry (EDS), and the influence of Re doping on the energy band structure of Mo3Sb7 was also analyzed by first-principles calculations. Effect on the Thermoelectric Properties of Mo3Sb7. The results show that when the doping amount is x≤0.1, Re uniformly doping in the lattice to form a solid solution and all the samples have no secondary phase impurities, while the cell parameters decrease with the increase of Re doping amount. Mo3Sb7 as a P-type three-dimensional conductive material, when every chemical unit of Mo3Sb7 additional access to two chemical units of valence electrons will be converted from metal to semiconductor. After Re doping, the Mo3Sb7 Fermi surface shifts up because Re has one more valence electron than Mo, but due to the limitation of solid solubility, Re doping does not make it into a semiconductor, and Re doping can not affect the Fermi surface energy The effect of band shape and band gap is also very limited. Due to the more valence electrons of Re, the introduction of Re reduces the conductivity of the compound Mo3Sb7 and increases its thermoelectric potential, and the decrease of conductivity will inevitably reduce the thermal conductivity contributed by the carriers, meanwhile Re doping The miscibility also increases the lattice thermal conductivity, so the total thermal conductivity of Mo3Sb7 is reduced. Finally, the thermoelectric properties are improved. Among them, after the Re-doped compound Mo2.90Re0.10Sb7 at 860 K ZT value of 0.127, 23.3% higher than the compound Mo3Sb7.