IR spectra and their application for evaluating physical properties of fluorophosphate glasses

Infrared (IR) absorbance spectra in the range 500-4000 cm(-1) of the glasse s in the system Ba(PO3)(2)-MgF2-CaF2-AlF3 have been studied with increasing fluoride content. Quantitative justification for assignment of some bands has been attempted. The spectra reveal that the glass structure changes wit h fluoride addition from metaphosphate, (PO3-)(n) to P-2 (O, F)(7) and P(O, F)(4) along with the formation of Al(O, F)(6), [AlF6](3-) and [AlF4](-). A s a result of these structural changes density (a), refractive index n,) an d IR band absorption coefficient at similar to 2170 cm(-1)(alpha (IR)) of t he glasses vary exhibiting maxima at similar to 36 mol% fluoride. Statistic al analyses show that d and n, are correlated with alpha (IR) by linear equ ations. Each of these equations gives a high correlation coefficient (r) an d low residual standard deviation (RSD), and may, thus, be employed for the evaluation of physical properties of fluorophosphate glasses. Physical pro perties of some fluorophosphate glasses of this work and the published lite rature have been calculated by using these equations to test their validity . The experimental properties of the glasses present a very good fit of dat a within 95% confidence interval of the calculated mean values. These facts indicate the suitability of this IR spectroscopic method for the determina tion of physical properties of fluorophosphate glasses. (C) 2001 Elsevier S cience B.V. All rights reserved.