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NbCoSn_Pt.pdf (794.28 kB)
Improved Thermoelectric Performance in N-Type Half-Heusler NbCoSn by Heavy-Element Pt Doping
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submitted on 29.04.2020 and posted on 29.04.2020by Federico Serrano Sanchez, Ting Luo, Junjie Yu, Wenjie Xie, Gudrun Auffermann, Anke Weidenkaff, Tiejun Zhu, Xinbing Zhao, José A. Alonso, Baptiste Gault, Claudia Felser, Chenguang Fu
Half-Heusler compounds with a valence electron count of 18, including ZrNiSn, ZrCoSb, and NbFeSb, are good thermoelec-tric materials owing to favourable electronic structures. Previous computational studies had predicted a high electrical power factor in another half-Heusler compound NbCoSn, but it has not been extensively investigated experimentally. Herein, the synthesis, structural characterization, and thermoelectric properties of the heavy-element Pt-doped NbCoSn compounds are reported. Pt is found to be an effective dopant enabling the optimization of electrical power factor, simul-taneously leading to a strong point defect scattering of phonons, and thereby suppressing the lattice thermal conductivity. Annealing significantly improves the carrier mobility, which is ascribed to the decreased grain boundary scattering. As a result, a maximum power factor of ~3.4 mWm-1K-2 is obtained at 600 K. In conjunction with the reduced lattice thermal conductivity, a maximum figure of merit zT of ~0.6 is achieved at 773 K for the post-annealed NbCo0.95Pt0.05Sn, an increase of 100% compared to the undoped NbCoSn. This work highlights the important roles of the doping element and micro-structure on the thermoelectric properties of half-Heusler compounds