Structure of lanthanum and cerium phosphate glasses by the method of isomorphic substitution in neutron diffraction


Neutron diffraction was used to measure the total structure factors for several rare-earth ion R3+ (La3+ or Ce3+) phosphate glasses with composition close to RAl0.35P3.24O10.12. By assuming isomorphic structures, difference function methods were employed to separate, essentially, those correlations involving R3+ from the remainder. A self-consistent model of the glass structure was thereby developed in which the Al correlations were taken into explicit account. The glass network was found to be made from interlinked PO4 tetrahedra having 2.2(1) terminal oxygen atoms, OT, at 1.51(1) Angstrom, and 1.8(1) bridging oxygen atoms, OB, at 1.60(1) Angstrom. Rare-earth cations bonded to an average of 7.5(2) OT nearest neighbors in a broad and asymmetric distribution. The Al3+ ion acted as a network modifier and formed OT-A1-OT linkages that helped strengthen the glass. The connectivity of the R-centered coordination polyhedra was quantified in terms of a parameter f(s) and used to develop a model for the dependence on composition of the A1-OT coordination number in R-A1-P-O glasses. By using recent 17 A1 nuclear-magnetic-resonance data, it was shown that this connectivity decreases monotonically with increasing Al content. The chemical durability of the glasses appeared to be at a maximum when the connectivity of the R-centered coordination polyhedra was at a minimum. The relation of f(s) to the glass transition temperature, Tg, was discussed.

Publication DOI:
Divisions: College of Health & Life Sciences > School of Biosciences
Additional Information: ©2003 American Physical Society
Uncontrolled Keywords: neutron diffraction,oxygen atoms,nuclear magnetic resonance,glass
Publication ISSN: 1550-235X
Last Modified: 06 May 2024 07:09
Date Deposited: 26 Nov 2014 15:15
Full Text Link:
Related URLs: http://journals ... sRevB.68.054203 (Publisher URL)
PURE Output Type: Article
Published Date: 2003-08-08
Authors: Martin, Richard A. (ORCID Profile 0000-0002-6013-2334)
Salmon, Philip S.
Benmore, Chris J.
Fischer, Henry E.
Cuello, Gabriel J.



Version: Published Version

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