Crystal Structure, Thermal Expansivity and High-Temperature Vibrational Spectra on Natural Hydrous Rutile

• 作者: Dan Liu Jinhua Zhang Joseph R.Smyth Junfeng Zhang Sha Wang Xi Zhu Xiang Wang Yu Ye
• 来源期刊: 地球科学学刊（英文版）
• 年，卷（期）: 2020,（6）
• 页码范围: 1190-1199
• 页数: 10页
• 语种: 英文

摘要

A natural rutle sample was measured by in situ high-temperature X-ray diffraction (XRD) patterns, as well as Raman and Fourier transform infrared (FTIR). Crystal structure is refined on the sample with 1.4 mol.％ Fe and 510±120 ppmw. H2O. The unit-cell and TiO6 octahedral volumes are ex-panded by 0.7％–0.8％ for Fe3+ incorporation, as compared with the reported Ti-pure samples. The volu-metric thermal expansion coefficient (α, K-1) could be approximated as a linear function of T (K): 4.95(3)× 10-9×T+21.54(5)×10-6, with the averaged value α0=30.48(5)×10-6 K-1, in the temperature range of 300–1500 K. The internal Ti-O stretching (A1g and B2g) and O-Ti-O bending (Eg) modes show 'red shift', whereas the multi-phonon process exhibits 'blue shift' at elevated temperature. The rotational mode (B1g) for TiO6 octahedra is nearly insensitive to temperature variations. The OH-stretching bands at 3279 and 3297 cm-1 are measured by high-temperature spectroscopy experiments. Both the IR-active and Raman-active OH-stretching modes shift to lower frequencies at higher temperature, with the signal intensities decreas-ing. And after quenching, we expect about 43％ dehydration around 873 K, and 85％ dehydration at 1273 K for this hydrous sample.