IRON VALENCE AND COORDINATION IN PHOSPHATE-GLASSES AS STUDIED BY OPTICAL SPECTROSCOPY

Optical spectroscopy was employed to study iron phosphate glasses of t he general composition xFe(2)O(3)(100 - x)P2O5 (14 less than or equal to x less than or equal to 47 mol%). Cation vibrational properties sho wed that iron is predominantly present as iron(II) in glasses of lower total iron content and as iron(III) in glasses of higher total iron c ontent. In glasses containing 40 and 47 mol% Fe2O3 some of iron(III) i ons changed from octahedral to tetrahedral coordination. Increasing ir on content increased network disorder to the point where the structura l changes occur, i.e., where iron cations changed their charge or coor dination. (C) 1998 Elsevier Science B.V. All rights reserved.