Structural Features of Iron Phosphate Glasses

Author

Gaya Kanishka Marasinghe
Mevlut Karabulut
C. S. Ray, Missouri University of Science and TechnologyFollow
D. E. Day, Missouri University of Science and TechnologyFollow
Mark G. Shumsky
William B. Yelon, Missouri University of Science and TechnologyFollow
Corwin H. Booth
Patrick G. Allen
David K. Shuh

Abstract

The structures and valence states of iron ions in several iron phosphate glasses with batch compositions similar to 40Fe₂O₃-60P₂O₅ (mol%) have been investigated using Mössbauer spectroscopy, X-ray absorption fine-structure spectroscopy (XAFS), X-ray photoelectron spectroscopy (XPS), differential thermal (DTA) and thermo-gravimetric (TGA) analysis and X-ray and neutron diffraction. Mössbauer spectra show that a redox equilibria corresponding to an Fe(II)/[Fe(II) + Fe(III)] ratio of 0.2-0.4 is reached under processing conditions described in this paper. Even though the valence state of iron ions in the glass appears to be insensitive to the oxygen content in the melting atmosphere, the Fe(II) content can be increased within the observed range of redox equilibria by increasing the partial pressure of a reducing gas in the melting atmosphere. Large amounts of Fe(II), Fe(II)/[Fe(II) + Fe(III)] ≥ 0.4, appear to be detrimental to the glass-forming ability of the iron phosphate melts. The local structure of the iron phosphate glasses appears to be related to the short range structure of crystalline Fe₃(P₂O₇)₂ which consists of a network of (Fe₃O₁₂)^-16 clusters. These clusters consist of one iron(II) ion and two iron(III) ions in sixfold coordination with near-neighbor oxygen ions. The (Fe₃O₁₂)^-16 clusters are interconnected via (P₂O₇)^-4 groups. Compared to other phosphate glasses, the proposed structure for iron phosphate glasses contain a smaller number of P-O-P bonds, a feature which is believed to be responsible for the unusually good chemical durability of iron phosphate glasses.

Recommended Citation

G. K. Marasinghe et al., "Structural Features of Iron Phosphate Glasses," Journal of Non-Crystalline Solids, vol. 222, pp. 144 - 152, Elsevier, Dec 1997.

The definitive version is available at https://doi.org/10.1016/S0022-3093(97)90107-1

Department(s)

Materials Science and Engineering

Keywords and Phrases

Chemical bonds; Crystal structure; Differential thermal analysis; Iron compounds; Melting; Mossbauer spectroscopy; Neutron diffraction; Pressure effects; Redox reactions; Thermogravimetric analysis; X ray diffraction analysis; X ray photoelectron spectroscopy; Iron phosphate; Redox equilibria

International Standard Serial Number (ISSN)

0022-3093; 1873-4812

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 1997 Elsevier, All rights reserved.

Publication Date

01 Dec 1997