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

Crystal Structure, Vibrational Spectra on Trivalent-Cation-Doped Rutile and Application in Optical Materials

“…The multi-phonon process, caused by the anharmonic feature and disorder in structure, is observed as a broad “hump” around 230–240 cm –1 for these phases. The B 2g band (symmetric Ti–O stretching) has not been clearly detected for these synthetic rutile samples but was observed for a naturally occurred one as a weak and broad peak around 810 cm –1 . The Raman shifts of the E g and A 1g bands for the Cr 3+ -doped rutile are 9 and 4 cm –1 lower, respectively, than those for the pure TiO 2 due to the larger Cr 3+ radius and the high Cr 3+ concentration.…”

“…The B 2g band (symmetric Ti−O stretching) has not been clearly detected for these synthetic rutile samples but was observed for a naturally occurred one as a weak and broad peak around 810 cm −1 . 18 The Raman shifts of the E g and A 1g bands for the Cr 3+ -doped rutile are 9 and 4 cm −1 lower, respectively, than those for the pure TiO 2 due to the larger Cr 3+ radius and the high Cr 3+ concentration. However, these differences are insignificant for the other M-doped samples (Supplementary Table S4).…”

“…When the population of M 3+ is higher than that of H + , the excess M 3+ cations may prefer to occupy the interstitial sites, like in the case of Al-doped rutile. ,, This is consistent with the experimental finding that the concentrations % bulk oxygen vacancies ( V O ) are very low in rutile and can be entirely replaced by OH – groups even under modest p H 2 O conditions. − In addition, incorporation of metallic cations further affects the hydrogen behaviors as reflected by Fourier transform infrared (FTIR) spectra. For example, the intrinsic OH-stretching mode in hydrous rutile is typically observed at 3279 cm –1 as caused by the reduction of Ti 4+ , while incorporation of Fe 3+ introduces another OH band at a higher frequency of 3297 cm –1 …”

“…For example, the intrinsic OH-stretching mode in hydrous rutile is typically observed at 3279 cm −1 as caused by the reduction of Ti 4+ , while incorporation of Fe 3+ introduces another OH band at a higher frequency of 3297 cm −1 . 18 Besides its geological and mineralogical importance, rutile also has longstanding wide application in physics, chemistry, and material science, such as in photocatalysts, solar cells, optical coatings, gas sensors, etc. 19−21 Its defect structure with reduction or cation substitution has also attracted extensive interests in applied physics and material science, particularly for optical materials.…”

Crystal structures and high-temperature and high-pressure vibrational spectra of synthetic fluorine-bearing brucites

“…The analyzer was equipped with a 600-w rotating Mo-anode X-ray source and a Saturn 724 HG CCD detector (with a resolution of 1024×1024), and the X-ray source was operated at a voltage of 50 kV and a current of 20 mA. We collected the intensity data in a 2θ scanning range of up to 52°, and the averaged wavelength of Mo K α1 -K α2 was calibrated to 0.71073 Å (Wang et al 2020). The intensity data collection and refined unit-cell parameters are listed in Table 2.…”