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

The relative distribution of rare-earth ions [Formula presented] ([Formula presented] or [Formula presented]) in the phosphate glass [Formula presented] was measured by employing the method of isomorphic substitution in neutron diffraction. It is found that 7.9(7) [Formula presented] nearest neighbors reside at 5.62(6) Å in a network made from interlinked [Formula presented] 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.