Raman spectra and structure of fluoro aluminophosphate glasses

Citation
Lf. Santos et al., Raman spectra and structure of fluoro aluminophosphate glasses, J NON-CRYST, 284(1-3), 2001, pp. 43-48
Citations number
12
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
JOURNAL OF NON-CRYSTALLINE SOLIDS
ISSN journal
00223093 → ACNP
Volume
284
Issue
1-3
Year of publication
2001
Pages
43 - 48
Database
ISI
SICI code
0022-3093(200105)284:1-3<43:RSASOF>2.0.ZU;2-1
Abstract
Fluoroaluminophosphate glasses are promising materials for rare earth dopin g, but their structure is not yet well known. The structural changes which take place in the 39AlF(3)-11 NaF-10LiF-(40 - x)(CaF2-MgF2- SrF2-BaF2)-xNaP O(3) system, with increasing NaPO3 content (0-15 mol%), have been studied b y polarised Raman and also infrared reflectance spectroscopies. The Raman s pectra of the glasses, at low-phosphate content, presented a polarised band peaking near 520 cm(-1), with a shoulder on the high-frequency side, which was the band with the largest amplitude. This band could be deconvoluted i nto three Gaussian functions near 515, 570 and 620 cm(-1), assigned to octa hedral [AIF(6)], five-coordinated [AIF(5)] and tetrahedral [AIF(4)] structu ral units, respectively. The addition of NaPO3 appeared to promote the form ation of [AIF(5)] units up to 3 mol% and to increase the conversion of [AIF (4)] and [AIF(5)] into [AIF(6)] octahedra, beyond 3 mol% of NaPO3. A pictur e has emerged for the structure of these ionic glasses, in which, for the l ow-phosphate content, the largest fraction of structural units are [AIF(4)] tetrahedra, containing both bridging and non-bridging fluorine, some of wh ich are replaced by [AIF(6)] octahedra, surrounded mostly by nonbridging fl uorine, as the NaPO3 content increases, bonded to short phosphate chains. ( C) 2001 Elsevier Science B.V. All rights reserved.