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The influence of fluorine on cationic and anionic ordering in the mica mineral phlogopite has been investigated using  29 Si,  1 H, and  19 F MAS as well as { 1 H}/{ 19 F} → 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 { 1 H}/{ 19 F} →  29 Si CPMAS NMR spectroscopies. The ordering effect in these two basic structural clusters can also be proven by a smaller  29 Si linewidth in the { 19 F} →  29 Si CPMAS NMR experiments compared to the usual  29 Si MAS NMR experiment showing a stronger ordering of Si environments near the two different anion types fluorine and hydroxyl. Intensities of the { 1 H}/{ 19 F} →  29 Si 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 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.

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