Crystal Structure, Thermal Expansivity and High-Temperature Vibrational Spectra on Natural Hydrous Rutile
Sha Wang, Jinhua Zhang, Joseph R. Smyth, Junfeng Zhang, Dan Liu, Xi Zhu, Xiang Wang, Yu Ye
Journal of Earth Science ›› 2020, Vol. 31 ›› Issue (6) : 1190-1199.
Crystal Structure, Thermal Expansivity and High-Temperature Vibrational Spectra on Natural Hydrous Rutile
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 expanded by 0.7%–0.8% for Fe3+ incorporation, as compared with the reported Ti-pure samples. The volumetric 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 α 0=30.48(5)×10−6 K−1, in the temperature range of 300–1500 K. The internal Ti-O stretching (A 1g and B 2g) and O-Ti-O bending (E g) modes show ‘red shift’, whereas the multi-phonon process exhibits ‘blue shift’ at elevated temperature. The rotational mode (B 1g) for TiO6 octahedra is nearly insensitive to temperature variations. The OH-stretching bands at 3 279 and 3 297 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 decreasing. And after quenching, we expect about 43% dehydration around 873 K, and 85% dehydration at 1 273 K for this hydrous sample.
rutile / crystal structure / thermal expansivity / high-temperature Raman / high-temperature FTIR / OH-stretching mode
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Sato, Y., 1977. Equation of State of Mantle Minerals Determined through High-Pressure X-Day Study. High Pressure Research Applications in Geophysics, (1977): 307–323. https://doi.org/10.1016/b978-0-12-468750-9.50028-0
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
/
〈 |
|
〉 |