@article{Zhao2025, 
author = {Kaiyue Zhao and Peixian Zhang and Yixin Jiao and Fei Wang and Juan Guo and Yongqiang Qiao and Qiang Sun and Qilong Gao},
title = {Synthesis, electronic property, and negative thermal expansion in cubic CaTiF6},
year = {2025},
journal = {Nano Research},
volume = {18},
number = {3},
pages = {94907236},
keywords = {chemical synthesis, negative thermal expansion, fluorides, first principles calculations},
url = {https://www.sciopen.com/article/10.26599/NR.2025.94907236},
doi = {10.26599/NR.2025.94907236},
abstract = {Double ReO3-type fluorides exhibit greater structural flexibility and elemental tunability than their single ReO3-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 CaTiF6 more facilely with inexpensive CaCl2 and H2TiF6. 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 of αl = −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 CaTiF6 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 CaTiF6, which dramatically promotes the development of Ti-based fluorides.}
}