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Study of the Electronic Structure and Transport Performance of the Skutterudites

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Tutor: ZhangQingJie
School: Wuhan University of Technology
Course: Materials Science
Keywords: thermoelectric materials,the first principle,electronic structure,transportprope
Type: Master's thesis
Year:  2012
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CoSb3skutterudites is a promising thermoelectric material used in medium temperature, it has high electrical conductivity and Seebeck coefficient, yet its high thermal conductivity makes its overall thermoelectric performance is not very high. Therefore, reducing the thermal conductivity of CoSb3skutterudites can significantly improve the thermoelectric performance. At the present, the reasonable approach to reduce the thermal conductivity of CoSb3skutterudites effectively is filling and doping, but the composition with which could have the optimal thermoelectric performance remains unclear. In this paper, the first principle calculation based on Boltzmann transport theory have been carried out to investigate the lattice structures, electronic structures and transport properties of different atomic filled CoSb3and different amount of Te doped CoSb3.For Ba, In filled CoSb3, the first principle calculation results reveal that Ba, In filling make the lattice constant expanded, while Ba, In double filled reduces the lattice order of the CoSb3; the filling of Ba and In atoms influence the forbidden band and conduction band greatly. The consequence of transport performance reveal that Ba, In double filled CoSb3has more appropriate Seebeck coefficient and electrical conductivity, and better power factor compared with those of Ba, In single filled CoSb3.For Ro.25Ko.25Co4Sbi2(R=Eu, Gd, Nd, Pr, Sm, Yb) skutterudites, the first principle calculation results show that the filling of K and the rare-earth elements make the lattice constant expanded and become bigger similarly, but the lattice constants of them are very close. Besides, the filling atoms also have influence on the forbidden band and conduction band. The bottom features of the conduction band for Gd0.25K0.25Co4Sb12, Ndo.25Ko.25Co4Sb12and Pr0.25K0.25Co4Sb12are similar, while contrastively, Eu0.25K0.25Co4Sb12, Sm0.25K0.25Co4Sb12and Yb0.25K0.2sCo4Sb12have smoother bottom of the conduction band. Particularly, Eu0.2sKo.25Co4Sb12and Sm0.25K0.25Co4Sb12also has similar bottom features of the conduction band. The transport performance results demonstrate that Eu0.25K0.25Co4Sb12and 5Ko.25Co4Sbi2have better thermoelectric performance.For Co4Sb12-xTex (x=0.25,0.5,0.75,1) thermoelectric materials, the first principle calculation results show that Te-doping leads to the increasing of the lattice constant of CoSb3skutterudites, and there is a positive correlation between the lattice constant and the amount of Te-doping. Moreover, different Te-doped CoSb3have different bandgap, and the Te-doping makes the conduction band bottom smoother. In addition, the curves of partial density of state for four kinds of Te doped CoSb3are similar. The transport performance results reveal that the thermoelectric performance of reach the best when the amount of Te doping equals0.5, which indicates that the appropriate amount of Te-doping may improve the performance of CoSb3skutterudites.
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