19F high speed MAS NMR investigation of octahedron connectivity in fluoroaluminate glasses

The Relationship Between 27Al Quadrupolar Parameters and AlF63– Octahedron Connectivity in Crystalline and Glassy Fluoroaluminates

“…In a previous 19 F NMR study [34] the β parameter, which gives the mean number of F atoms per octahedron, was found to equal 6 for the glass with 35 % AlF 3 content. Therefore, it can be stated that the glassy structure contains isolated AlF 6 3-octahedra only.…”

“…For the glass comprising 50 % AlF 3 , we should assume the presence of ramified chains (β Ͻ 5) rather than infinite chains (β = 5), as previously deduced from our 19 F NMR study. [34] Conclusion 27 Al SATRAS and 3Q-MAS spectra (for compounds with several Al sites) were recorded for eight crystalline compounds from binary CaF 2 -AlF 3 and BaF 2 -AlF 3 and ternary BaF 2 -CaF 2 -AlF 3 systems, and four glass compositions with different CaF 2 /BaF 2 /AlF 3 contents.…”

“…These results are discussed in the light of a recent 19 F NMR study on the same glassy phases, [34] which led to the experimental determination of the mean number, β, of fluorine atoms per AlF 6 3-octahedron. It was shown that the β value is between 6 and 5 for the studied glasses, and is dependent on the amount of AlF 3 in the glass (35-50 %).…”

“…Information regarding the glass formation area is reported in ref. [34] High-Resolution Solid-State NMR: The high-resolution 27 Al NMR spectra were recorded at 78.2 MHz with a Bruker Avance 300 spectrometer. CP MAS probes with 4 mm and 2.5 mm rotors were used for low and high spinning speeds, respectively.…”

“…[ 34] Four of these compositions have been chosen for this study, and contain 35-50 % AlF 3 . The selected glass compositions are given in Table 2.…”