Abstract We report 93Nb and 121Sb NMR and 57Fe Mossbauer studies combined with DFT calculations of Nb1−xTixFeSb (0 ≤ x ≤ 0.3), one of the most promising thermoelectric systems for applications above 1000 K. These studies provide local information about defects and electronic configurations in these heavily p-type materials. The NMR spin-lattice relaxation rate provides a measure of states within the valence band. With increasing x, changes of relaxation rate vs carrier concentration for different substitution fractions indicate the importance of resonant levels which do not contribute to charge transport. The chemical shift is significantly larger than expected based on DFT calculations, which we discuss in terms of an enhancement of the susceptibility due to a Coulomb enhancement mechanism. The Mossbauer spectra of Ti-substituted samples show small departures from a binomial distribution of substituted atoms, while for unsubstituted p-type NbFeSb, the amplitude of a Mossbauer satellite peak increases vs temperature, a measure of the T-dependent charging of a population of defects residing about 30 meV above the valence band edge, indicative of an impurity band at this location.

中文翻译：

---

半赫斯勒 Nb1−Ti FeSb 中的缺陷充电和共振水平

摘要 我们报告了 93Nb 和 121Sb NMR 和 57Fe Mossbauer 研究与 Nb1−xTixFeSb (0 ≤ x ≤ 0.3) 的 DFT 计算相结合，Nb1−xTixFeSb (0 ≤ x ≤ 0.3) 是用于 1000 K 以上应用的最有前途的热电系统之一。这些研究提供了有关缺陷和电子配置的局部信息在这些重 p 型材料中。NMR 自旋晶格弛豫率提供了价带内状态的量度。随着 x 的增加，不同取代分数的弛豫率与载流子浓度的变化表明共振水平的重要性，这对电荷传输没有贡献。化学位移显着大于基于 DFT 计算的预期，我们根据由于库仑增强机制导致的磁化率增强来讨论。