Effect of Melting Temperature and Time on Iron Valence and Crystallization of Iron Phosphate Glasses

Abstract

The effect of melting temperature and time on iron valence, dissolution rate (DR) in deionized water, and crystallization of iron phosphate glasses was investigated using a 40Fe2O3-60P2O5, mol%, batch composition. The concentration of Fe2+ ions in these glasses increased from 17% to 57% as melting temperature increased from 1150°C to 1450°C, but remained nearly constant at about 20% for melting times longer than 1 h at 1200°C. Measurements by differential thermal analysis (DTA) combined with X-ray diffraction (XRD) and thermogravimetric analysis (TGA) showed that these glasses crystallized to Fe3(P2O7)2 and Fe4(P2O7)3 when heated in nitrogen between 600°C and 820°C, but with continued heating in air at 820°C the Fe3(P2O7)2 changed to Fe(PO4), which produced a weight gain in the sample associated with the oxidation of Fe2+ to Fe3+ ions. The DR (in deionized water) of these glasses was generally very low (not, vert, similar10−9 g cm−2 min−1) and nearly independent of the relative concentration of Fe2+ or Fe3+ ions, but decreased with total iron content.

Department(s)

Materials Science and Engineering

Sponsor(s)

United States. Department of Energy

International Standard Serial Number (ISSN)

0022-3093; 1873-4812

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 1999 Elsevier, All rights reserved.

Publication Date

01 Jul 1999

Link to Full Text

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