Aluminum ordering and clustering in Al-rich synthetic phlogopite: The influence of fluorine investigated by {F-19/H-1} Si-29 CPMAS NMR spectroscopy

作者：Fechtelkord Michael^*; Langner Ramona

来源：American Mineralogist, 2013, 98(1): 120-131.

DOI：10.2138/am.2013.3885

• H-1
• F-19
• Si-29
• solid state
• NMR
• MAS
• CPMAS
• depolarization
• phlogopite
• fluorine

The influence of fluorine on cationic and anionic ordering in the mica mineral phlogopite has been investigated using Si-29, H-1, and F-19 MAS as well as {H-1}/{F-19} -%26gt; Si-29 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 {H-1}/{F-19} -%26gt; Si-29 CPMAS NMR spectroscopies. The ordering effect in these two basic structural clusters can also be proven by a smaller Si-29 linewidth in the {F-19} -%26gt; Si-29 CPMAS NMR experiments compared to the usual Si-29 MAS NMR experiment showing a stronger ordering of Si environments near the two different anion types fluorine and hydroxyl. Intensities of the {H-1}/{F-19} -%26gt; Si-29 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 (T-2), the lambda parameter (lambda), and the proton/fluorine spin-lattice time in the rotating frame (T-1 rho)were extracted to give information about the local structure.

• 出版日期2013-1