Structure of AlPO4•AlF3•CaF2•BaF2 fluorophosphate glass

The structure of glass with a chemical composition of 15AlPO(4)center dot 40AlF(3)center dot 35CaF(2)center dot 10BaF(2) was studied among various fluorophosphates glasses. Structural analyses of the glass were performed using Raman scattering spectroscopy, Al-27 and P-31 magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy, total correlation function derived from x-ray diffraction measurements and classical molecular dynamics simulations. By optimising the parameters of the Born-Mayer potentials used in the simulations, a structural model, which reproduced the total correlation function and satisfied the structural information obtained using the Raman and NMR spectra, was obtained. The coordination number of Al atoms in the structural model was approximately six. One O atom and five F atoms were present in the average coordination polyhedron. Almost all O atoms were bonded to P atoms, and the tetrahedral PO4 units were bonded to three or four Al atoms. A P-O-Al oxide network and fluoride glass primarily composed of AlF3 were connected to an Al coordination polyhedron containing O and F atoms in the glass network structure.