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Issue 63, 2015
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Electronic structure and thermoelectric properties of the Zintl compounds Sr5Al2Sb6 and Ca5Al2Sb6: first-principles study

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Abstract

Previous experimental work showed that Zn-doping only slightly increased the carrier concentration of Sr5Al2Sb6 and the electrical conductivity improved barely, which is very different from the results of Zn-doping in Ca5Al2Sb6. To understand their different thermoelectric behaviors, we investigated their stability, electronic structure, and thermoelectric properties using first-principles calculations and the semiclassical Boltzmann theory. We found that the low carrier concentration of Zn-doped Sr5Al2Sb6 mainly comes from its high positive formation energy. Moreover, we predict that a high hole concentration can possibly be realized in Sr5Al2Sb6 by Na or Mn doping, due to the negative and low formation energies of Na- and Mn-doped Sr5Al2Sb6, especially for Mn doping (−6.58 eV). For p-type Sr5Al2Sb6, the large effective mass along ΓY induces a large Seebeck coefficient along the y direction, which leads to the good thermoelectric properties along the y direction. For p-type Ca5Al2Sb6, the effective mass along ΓZ is always smaller than those along the other two directions with increasing doping degree, which induces its good thermoelectric properties along the z direction. The analysis of the weight mobility of the two compounds confirms this idea. The calculated band structure shows that Sr5Al2Sb6 has a larger band gap than Ca5Al2Sb6. The relatively small band gap of Ca5Al2Sb6 mainly results from the appearance of a high density-of-states peak around the conduction band bottom, which originates from the Sb–Sb antibonding states in it.

Graphical abstract: Electronic structure and thermoelectric properties of the Zintl compounds Sr5Al2Sb6 and Ca5Al2Sb6: first-principles study

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Publication details

The article was received on 02 Feb 2015, accepted on 08 May 2015 and first published on 08 May 2015


Article type: Paper
DOI: 10.1039/C5RA02033F
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RSC Adv., 2015,5, 50720-50728

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    Electronic structure and thermoelectric properties of the Zintl compounds Sr5Al2Sb6 and Ca5Al2Sb6: first-principles study

    L. Ye, Y. X. Wang, J. Yang, Y. Yan, J. Zhang, L. Guo and Z. Feng, RSC Adv., 2015, 5, 50720
    DOI: 10.1039/C5RA02033F

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