We report , , and nuclear magnetic resonance measurements combined with density functional theory (DFT) calculations on a series of half-Heusler semiconductors, including NbCoSn, ZrCoSb, TaFeSb, and NbFeSb, to better understand their electronic properties and general composition-dependent trends. These materials are of interest as potentially high efficiency thermoelectric materials. Compared to the other materials, we find that ZrCoSb tends to have a relatively large amount of local disorder, apparently antisite defects. This contributes to a small excitation gap corresponding to an impurity band near the band edge. In NbCoSn and TaFeSb, Curie–Weiss-type behavior is revealed, which indicates a small density of interacting paramagnetic defects. Very large paramagnetic chemical shifts are observed associated with a Van Vleck mechanism due to closely spaced bands splitting between the conduction and valence bands. Meanwhile, DFT methods were generally successful in reproducing the chemical shift trend for these half-Heusler materials, and we identify enhancement of the larger-magnitude shifts, which we connect to electron interaction effects. The general trend is connected to changes in -electron hybridization across the series.
Half-Heusler thermoelectric materials: NMR studies
Yefan Tian, Nader Ghassemi, Wuyang Ren, Hangtian Zhu, Shan Li, Qian Zhang, Zhiming Wang, Zhifeng Ren, Joseph H. Ross; Half-Heusler thermoelectric materials: NMR studies. J. Appl. Phys. 7 August 2020; 128 (5): 055106. https://doi.org/10.1063/5.0018260
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