论文标题
半身热电材料：NMR研究
Half-Heusler thermoelectric materials: NMR studies
论文作者
论文摘要
We report $^{59}$Co, $^{93}$Nb, and $^{121}$Sb nuclear magnetic resonance (NMR) 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趋势。这些材料作为潜在的高效率热电材料而感兴趣。与其他材料相比，我们发现ZRCOSB倾向于具有相对较大的局部疾病，显然是反塞人缺陷。这有助于对应于带边缘附近的杂质带的小激发差距。在NBCOSN和TAFESB中，揭示了Curie-Weiss型行为，这表明相互作用的顺磁性缺陷密度很小。观察到非常大的顺磁化学移位与范弗莱克机制相关，这是由于离子间距紧密的$ d $带之间的传导和价带之间的分裂。同时，DFT方法通常在重现这些半手材料的化学移位趋势方面取得了成功，我们确定了更大的磁性移位的增强，我们将其连接到电子相互作用效应。总体趋势与整个系列的$ D $ - 电子杂交的变化有关。
We report $^{59}$Co, $^{93}$Nb, and $^{121}$Sb nuclear magnetic resonance (NMR) 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 $d$ 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 an enhancement of the larger-magnitude shifts, which we connect to electron interaction effects. The general trend is connected to changes in $d$-electron hybridization across the series.
