Wu Jinyu, Zhang JinFeng, Hu Xiaoxia, Xie Haijiao, Yan Liwen, Hou Feng, Liu Jiachen, Ma Xiaohui, Guo Anran
School of Materials Science and Engineering, Key Lab of Advanced Ceramics and Machining Technology of Ministry of Education, Tianjin University, Tianjin, 300072, China.
Hangzhou Yanqu, Information Technology Co., Ltd., Zhejiang, 310003, China.
Small. 2024 Jun;20(26):e2310615. doi: 10.1002/smll.202310615. Epub 2024 Jan 22.
High-entropy ceramics exhibit various excellent properties owing to their high configurational entropy, which is caused by multi-principal elements sharing one lattice site. The configurational entropy will further increase significantly if multi-principal elements randomly share two different lattice sites. For this purpose, pseudobrookite phase containing two cationic lattice sites (A and B sites) is selected, and corresponding high-entropy pseudobrookite (M M )TiO is synthesized. Herein, the distribution of the 2-valent and 3-valent cations in the A and B sites are analysed in depth. The distance between the A and B sites in the crystal structure models which are constructed by the Rietveld analysis is calculated and defined as distance d. Meanwhile, the atomic column positions in the STEM images are quantified by a model-based mathematical algorithm, and the corresponding distance d are calculated. By comparing the distance d, it is determine that the 2-valent and 3-valent cations are jointly and disorderly distributed in the A and B sites in high-entropy (M M )TiO. The density functional theory (DFT) simulations also demonstrate that this type of crystal structure is more thermodynamically stable. The higher degree of cationic disorder leads to a higher configurational entropy in high-entropy (M M )TiO, and endows high-entropy (M M )TiO with very low thermal conductivity (1.187-1.249 W m K).
高熵陶瓷由于其高组态熵而表现出各种优异性能，这种高组态熵是由多个主元素共享一个晶格位点所导致的。如果多个主元素随机共享两个不同的晶格位点，组态熵将进一步显著增加。为此，选择了含有两个阳离子晶格位点（A位和B位）的假板钛矿相，并合成了相应的高熵假板钛矿（M M ）TiO 。在此，对二价和三价阳离子在A位和B位的分布进行了深入分析。通过Rietveld分析构建的晶体结构模型中A位和B位之间的距离被计算出来并定义为距离d。同时，通过基于模型的数学算法对STEM图像中的原子列位置进行量化，并计算出相应的距离d。通过比较距离d，确定在高熵（M M ）TiO 中，二价和三价阳离子在A位和B位是联合且无序分布的。密度泛函理论（DFT）模拟也表明这种晶体结构在热力学上更稳定。阳离子无序程度越高，高熵（M M ）TiO 中的组态熵就越高，并赋予高熵（M M ）TiO 非常低的热导率（1.187 - 1.249 W m K）。
