Half-Heusler (HH) alloys are an important class of thermoelectric materials that combine promising performance with good engineering properties. This manuscript reports a variable temperature synchrotron x-ray diffraction study of several TiNiSn- and VFeSb-based HH alloys. A Debye model was found to capture the main trends in thermal expansion and atomic displacement parameters. The linear thermal expansion coefficient α(T) of the TiNiSn-based samples was found to be independent of alloying or presence of Cu interstitials with α _av = 10.1 10⁻⁶ K⁻¹ between 400 and 848 K. The α(T) of VFeSb and TiNiSn are well-matched, but NbFeSb has a reduced α _av = 8.9 10⁻⁶ K⁻¹, caused by a stiffer lattice structure. This is confirmed by analysis of the Debye temperatures, which indicate significantly larger bond force constants for all atomic sites in NbFeSb. This work also reveals substantial amounts of Fe interstitials in VFeSb, whilst these are absent for NbFeSb. The Fe interstitials are linked to low thermal conductivities, but also reduce the bandgap and lower the onset of thermal bipolar transport.

半赫斯勒 (HH) 合金是一类重要的热电材料，结合了良好的性能和良好的工程性能。这份手稿报告了几种基于 TiNiSn 和 VFeSb 的 HH 合金的变温同步加速器 X 射线衍射研究。发现德拜模型可以捕捉热膨胀和原子位移参数的主要趋势。线性热膨胀系数α（T）基于TiNiSn-样品被认为是独立的合金或Cu插页的存在的α _AV = 10.1 10 ^-6 ķ ^-1 400和K的之间848 α（T）的VFeSb 和 TiNiSn 匹配良好，但 NbFeSb 的α _av = 8.9 10^-6 K ^-1，由更硬的晶格结构引起。这通过对德拜温度的分析得到证实，德拜温度表明 NbFeSb 中所有原子位点的键力常数明显更大。这项工作还揭示了 VFeSb 中大量的 Fe 间隙，而 NbFeSb 不存在这些间隙。Fe间隙与低热导率有关，但也减少带隙并降低热双极传输的开始。