• journal_title：American Mineralogist
• Contributor：Michael Fechtelkord ; Ramona Langner
• Publisher：Mineralogical Society of America
• Date：2013-01-01
• Format：text/html
• Language：en
• Identifier：10.2138/am.2013.3885
• journal_abbrev：American Mineralogist
• issn：0003-004X
• volume：98
• issue：1
• firstpage：120
• section：Articles

The influence of fluorine on cationic and anionic ordering in the mica mineral phlogopite has been investigated using ²⁹Si, ¹H, and ¹⁹F MAS as well as {¹H}/{¹⁹F} → ²⁹Si CPMAS and CP-depolarization NMR spectroscopies. It can be shown that the mere presence of fluorine achieves a tremendous loss of capability to incorporate aluminum into the phlogopite structure. Fluorine is usually located in Mg-rich octahedral and Si-rich tetrahedral clusters of the phlogopite structure while hydroxyl groups are located in Al-rich octahedral and tetrahedral clusters as derived from {¹H}/{¹⁹F} → ²⁹Si CPMAS NMR spectroscopies. The ordering effect in these two basic structural clusters can also be proven by a smaller ²⁹Si linewidth in the {¹⁹F} → ²⁹Si CPMAS NMR experiments compared to the usual ²⁹Si MAS NMR experiment showing a stronger ordering of Si environments near the two different anion types fluorine and hydroxyl. Intensities of the {¹H}/{¹⁹F} → ²⁹Si CPMAS NMR signals as function of the contact-time show a deviation from the classical I-S model and can be attributed to the I-I*-S model. Time constants like the proton/fluorine spin diffusion time (T_df), the spin-spin relaxation time (T₂), the λ parameter (λ), and the proton/fluorine spin-lattice time in the rotating frame (T_1ρ) were extracted to give information about the local structure.