期刊
AMERICAN MINERALOGIST
卷 95, 期 10, 页码 1444-1457出版社
MINERALOGICAL SOC AMER
DOI: 10.2138/am.2010.3472
关键词
Muscovite; infrared spectroscopy; dehydroxylation; high temperature; phonon; hydroxyl
Temperature dependencies and thermal dynamical behavior of vibrational phonons related to different bonds/motions (e.g., K-O, Si-O, and Al-O) and O-H stretching, bending, and combinations bands, as well as those of NH4 ions, of muscovite have been investigated in detail at high temperatures using in situ infrared spectroscopy. Phonon modes of muscovite show a complex response to heating and dehydroxylation. The mode Gruneisen parameters of muscovite are largest for low-frequency bands and some bands have negative values. Approaching dehydroxylation, bands associated with K-O stretching, Al-OH bending, and Al-O vibrations exhibit significant variations, indicating modifications of local configurations related to these ions. The O-H stretching feature near 3627 cm(-1) shows a change in temperature dependence of the peak position near or during dehydroxylation, and this is attributed to a dramatic loss of OH and changes in local environments. The infrared spectro-scopic analyses carried out in situ or on quenched samples do not record the characteristic bands of dehydroxylation-induced H2O and these findings suggest that H2O is unlikely to be the principal diffusing species. The results suggest that de-ammoniation or loss of NH4 in muscovite takes place at temperatures near dehydroxylation.
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