Identification of the Relative Distribution of Rare-Earth Ions in Phosphate Glasses

The relative distribution of rare-earth ions R³⁺ (Dy³⁺ or Ho³⁺) in the phosphate glass RAl0.30P3.05O9.62 was measured by employing the method of isomorphic substitution in neutron diffraction. It is found that 7.9(7) R-R nearest neighbors reside at 5.62(6) {} in a network made from interlinked PO₄ tetrahedra. Provided that the role of Al is explicitly considered, a self-consistent account of the local matrix atom correlations can be developed in which there are 1.68(9) bridging and 2.32(9) terminal oxygen atoms per phosphorus.