Xue Zefan, Lu Weichao, Cui Wenjun, Lin Weixiao, Sun Congli, Sang Xiahan
NRC (Nanostructure Research Centre), Wuhan University of Technology, Wuhan 430070, China.
State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China.
ACS Appl Mater Interfaces. 2024 Jun 12;16(23):30598-30606. doi: 10.1021/acsami.4c06274. Epub 2024 May 31.
Interdiffusion and solid-solid phase reaction at the interface between thermoelectric (TE) materials and the electrode critically influence interfacial transport properties and the overall energy conversion efficiency during service. Here, the microstructural evolution and diffusion mechanisms at the interfaces between the most widely used BiTe-based TE materials, n-type BiTeSe (BTS) and p-type BiSbTe (BST), and Ni electrodes were investigated at atomic resolution using spherical aberration-corrected scanning transmission electron microscopy (STEM). The BTS(0001)/Ni and BST(0001)/Ni interfaces were constructed by depositing Ni nanoparticles on mechanically exfoliated BTS and BST bulk materials and subsequent annealing. The interfacial reaction is initially dominated by Ni diffusion into the TE matrix to form NiAs-type NiM intermetallics, while Ni trans-quintuple-layer diffusion only occurs in Sb-rich BST. The Bi-rich BTS is more influenced by the Ni-Te preferential reaction, resulting in NiM abnormal grain growth and the formation of tilted and rotated interfaces. Bi diffusion into the BTS matrix forms a Bi double layer at the interface or Bi[Bi(Te,Se)] as the annealing temperature increases, while Bi diffusion into the Ni thin film greatly accelerates the interfacial reaction rate, as elucidated by in situ heating STEM. The results provide essential structural details to understand and prevent the degradation of TE device performance.
热电（TE）材料与电极之间界面处的互扩散和固-固相反应严重影响服役期间的界面传输性能和整体能量转换效率。在此，利用球差校正扫描透射电子显微镜（STEM）在原子分辨率下研究了最广泛使用的BiTe基TE材料、n型BiTeSe（BTS）和p型BiSbTe（BST）与Ni电极之间界面处的微观结构演变和扩散机制。通过在机械剥离的BTS和BST块状材料上沉积Ni纳米颗粒并随后退火来构建BTS(0001)/Ni和BST(0001)/Ni界面。界面反应最初以Ni扩散到TE基体中形成NiAs型NiM金属间化合物为主，而Ni跨五重层扩散仅发生在富Sb的BST中。富Bi的BTS受Ni-Te优先反应的影响更大，导致NiM异常晶粒生长以及倾斜和旋转界面的形成。随着退火温度升高，Bi扩散到BTS基体中在界面处形成Bi双层或Bi[Bi(Te,Se)]，而Bi扩散到Ni薄膜中极大地加速了界面反应速率，原位加热STEM对此进行了阐明。这些结果为理解和防止TE器件性能退化提供了重要的结构细节。
