Synthesis,electronic property,and negative thermal expansion in cubic CaTiF_(6)  

作　　者：Kaiyue Zhao Peixian Zhang Yixin Jiao Fei Wang Juan Guo Yongqiang Qiao Qiang Sun Qilong Gao 

机构地区：[1]Key Laboratory of Materials Physics of Ministry of Education,and School of Physics and Microelectronics,Zhengzhou University,Zhengzhou 450052,China

出　　处：《Nano Research》2025年第3期333-340,共8页纳米研究(英文版)

基　　金：supported by the National Natural Science Foundation of China(Nos.22071221 and 12374032);China Postdoctoral Science Foundation(No.2023M743152);the Natural Science Foundation of Henan Province(No.242300421376);All calculations were supported by the National Supercomputing Center in Zhengzhou.

摘　　要：Double ReO_(3)-type fluorides exhibit greater structural flexibility and elemental tunability than their single ReO_(3)-type counterparts,drawing widespread interest in applications involving negative thermal expansion(NTE)and optics.However,their applications are extremely constrained by the scarcity of the materials themselves,the harsh preparation conditions,and the high cost of the requisite raw materials.In this work,we have successfully obtained the cubic phase CaTiF_(6)more facilely with inexpensive CaCl_(2) and H2TiF_(6).The ultraviolet-visible(UV-vis)absorption spectrum indicates a bandgap of 3.6 eV and semiconducting properties.Raman spectroscopy analysis reveals the structure from rhombic to cubic transformation around 138 K,accompanied by a significant isotropic NTE in the cubic phase,with a coefficient ofαl=−7.26×10^(−6)K^(−1)(175-475 K).Theoretical calculations based on first principles indicate that the semiconducting properties originate from the hybridization of the 3d orbit of Ti and the 2p orbit of F.The driving force for NTE in CaTiF_(6)comes from the transverse thermal vibrations of fluorine atoms,as confirmed by density functional theory(DFT)calculation.This research provides a novel,facile,and cost-effective synthetic way and reveals in depth the electronic properties and NTE mechanism of CaTiF_(6),which dramatically promotes the development of Ti-based fluorides.

关 键 词：negative thermal expansion fluorides chemical synthesis first principles calculations 

分 类 号：O62[理学—有机化学]