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热电材料能够直接实现热能与电能之间的转化，是一种极具潜力的能源转化材料。在众多热电材料中，半赫斯勒材料同时具有优异的热电性能和力学性能，十分有潜力开发先进的热电器件，但是目前制约其发展的主要阻碍是其固有的脆性以及有限的延展性。如果能够在半赫斯勒热电材料中发现一定的延展性，将有利于开发相应的柔性热电器件，为生产可穿戴型的能源转化器件提供基础材料。在面心立方结构中，其剪切过程中存在的剪切诱导“抓紧键”现象能够使材料表现出良好的延展性。而半赫斯勒材料的晶体结构就是三层嵌套的面心立方结构，其晶体结构中可能同样存在剪切诱导“抓紧键”现象，使其具有潜在优异的延展性。
Fig. 1 | Shear stress-strain response of XFeSb (X = Nb, Ta) and SnNiY (Y = Ti, Zr, Hf) along the (111)/<–1-12> slip system.
来自武汉理工大学理学院的李国栋教授团队，使用第一性原理方法研究了TaFeSb半赫斯勒热电材料的剪切响应，发现了剪切诱导“抓紧键”现象，该“抓紧键”现象被认为是不全位错导致的连续滑移，使材料具有良好的延展性。该研究除了研究了TaFeSb的剪切响应外，还在具有相同结构特征的NbFeSb中同样发现了剪切诱导“抓紧键”现象，而在SnNiY (Y = Ti, Zr, Hf)的剪切响应中，晶体结构逐渐软化来释放应力，两者的差异主要来源于是否发生了晶面解离。最终，剪切诱导“抓紧键”现象被认为是晶体结构沿特定滑移面发生化学键断裂后出现的连续滑移。
Fig. 2 | The atomic configurations and dynamic chemical bonds length of TaFeSb before first stress releasing process during the (111)/<–1-12> shear.
该研究团队揭示了半赫斯勒热电材料潜在的延展性及其本质。相关论文近期发表于npj Computational Materials 10:61 (2024)。
Fig. 3 | The generalized stacking fault energy calculations model and generalized stacking fault energy results of TaFeSb.
该研究团队揭示了半赫斯勒热电材料潜在的延展性及其本质，论文近期发表于npj Computational Materials 10:61 (2024)，英文标题与摘要如下，点击左下角“阅读原文”可以自由获取论文PDF。
Origin of shear induced ‘catching bonds’ on half Heusler thermoelectric compounds XFeSb (X = Nb, Ta) and SnNiY (Y = Ti, Zr, Hf)
Haoqin Ma, Xiege Huang, Zhongtao Lu, Xiaobin Feng, Bo Duan,
Wenjuan Li, Yinhan Liu, Pengcheng Zhai, Guodong Li, Qingjie Zhang
Half Heusler materials exhibit excellent thermoelectric and mechanical properties, rendering them potential candidates for advanced thermoelectric devices. Currently, the developments on interrelated devices are impeded by their inherent brittleness and limited ductility. Nevertheless, it exists the potential ductility on half Heusler materials with face-centered cubic sub-lattices through the expectation on the occurrence of shear induced ‘catching bonds’ which can result in excellent ductility on other face centered cubic materials. In this work, focus on half Heusler thermoelectric materials XFeSb (X = Nb, Ta) and SnNiY (Y = Ti, Zr, Hf), the shear deformation failure processes are deeply investigated through the first principle calculations. Shear induced ‘catching bonds’ are found on XFeSb (X = Nb, Ta) along the (111)/<-1-12> slip system, which releasing the internal stress and exactly resulting in the potential ductility. According to the thermodynamic criterion based on generalized stacking fault energy, the essence of shear induced ‘catching bonds’ are interpreted as the (111)/<-110> slips formed by several 1/3(111)/<-1-12> partial dislocations motions. During the (111)/<-1-12> shear on SnNiY (Y = Ti, Zr, Hf), the structural integrity is maintained without inducing ‘catching bonds’. Different deformation processes occurred in the identical crystal structure are elucidated through the energy explanation, revealing that shear induced ‘catching bonds’ originate from the crystal plane cleavage on the (111) plane. The present works offer significant advantageous for the assessment and comprehension of shear induced ‘catching bonds’ in other materials, and facilitate the developments of XFeSb (X = Nb, Ta)-based thermoelectric devices with excellent ductility.
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