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Solid Solutions CaF2–YF3 with Fluorite Structure Prepared on the Sol–Gel Route: Investigation by Multinuclear MAS NMR Spectroscopy

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journal contribution
posted on 11.09.2014, 00:00 by Thoralf Krahl, Gudrun Scholz, Erhard Kemnitz
Nanoscaled Ca1–xYxF2+x (x = 0...0.40) was prepared on the new fluorolytic sol–gel route using organic precursors and anhydrous HF. These nonstoichiometric fluorite-type phases were investigated using 19F MAS and 19F–89Y CP MAS NMR. Excess fluoride ions occur as point defects for x ≤ 0.01. For x > 0.01 excess fluoride ions start clustering. The 19F spectra of these phases can be fully explained by assuming a distribution of Ca2+ and Y3+ around fluoride ions. Y3+ is distributed within the crystal lattice of CaF2, with higher concentrations near fluoride clusters. Two different coordination polyhedra for Y3+ are observed. The correlation between 19F and 89Y signals was established.