Abstract
Rare earth phosphate glasses with molar compositions xRE2O3 (1-x)P2O5 (0≤x0.30) were prepared and characterized by extended x-ray absorption fine structure (EXAFS) spectroscopy and by high-energy x-ray diffraction (XRD) analyses. The analyses indicate that the average coordination number (CN) of the RE3+ ions depends on composition: ultraphosphate glasses with less than -15 mole% RE2O3 have average RE CN's of 8-9 and CN decreases to -6 with increasing RE2O3 content to 25 mole%. The compositional dependence of RE CN can be understood with a simple model in which the formation of structurally isolated RE-polyhedra is favored in ultraphosphate glasses. Glass properties, including refractive index and glass transition temperature, are sensitive to changes in glass structure.
