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Article
Structure of Rare-Earth Phosphate Glasses by X-ray and Neutron Diffraction
Journal of Non-Crystalline Solids
  • Richard K. Brow, Missouri University of Science and Technology
  • Uwe Hoppe
  • D. Illeva
  • P. Jovari
  • A. C. Hannon
Abstract

Previous diffraction studies of the structures of rare-earth phosphate glasses (R2O3)x(P2O5)1−x are extended to glasses with smaller R3+ ions with R = Sm, Gd, Dy, Er, Yb, Y for x = not, vert, similar0.25 and with R = Nd, Sm, Gd for x = not, vert, similar0.15. Parameters for the P-O, R-O and O-O first-neighbor peaks were obtained by Gaussian fitting. P-P and R-P distances were estimated from the positions of peak maxima. Effects of residual silica or alumina contents present as a result of glass processing were taken into account for selected samples. The P-O coordination number, NPO, and the P-O, O-O, P-P distances are consistent with the presence of phosphate tetrahedra and are insensitive to the R species and the R2O3 content. Rare-earth coordination numbers, NRO, decrease from not, vert, similar8 to not, vert, similar6.5 when x is increased from not, vert, similar0.15 to not, vert, similar0.25. NOO and NPP decrease with increasing R2O3 content indicating the network disintegration. The numbers NRO of the metaphosphate glasses (x = not, vert, similar0.25) decreases from not, vert, similar7 to not, vert, similar6 when R is changed from La to Yb. This change is also indicated by the behavior of the R-O distances and by constant number densities of atoms. The decrease in NRO with increasing R2O3 content is due to the reduction in the number of terminal O (OT) available for coordination of the R3+ ions (six at metaphosphate composition). Especially for smaller R3+ ions sharing OT between two R sites is not favored. The decrease by not, vert, similar0.04 nm of the prominent R-R first-neighbor distance with a change of R from La to Yb at the metaphosphate composition is indicated by a shift to higher magnitude of scattering vector of the shoulder occurring in front of the first main diffraction peak.

Department(s)
Materials Science and Engineering
Keywords and Phrases
  • Structure,
  • X-Ray and Neutron Diffraction,
  • Rare-Earth Phosphate Glass
Document Type
Article - Journal
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2005 Elsevier Inc., All rights reserved.
Publication Date
10-15-2005
Publication Date
15 Oct 2005
Citation Information
Richard K. Brow, Uwe Hoppe, D. Illeva, P. Jovari, et al.. "Structure of Rare-Earth Phosphate Glasses by X-ray and Neutron Diffraction" Journal of Non-Crystalline Solids (2005) ISSN: 0022-3093; 1873-4812
Available at: http://works.bepress.com/richard-brow/143/