Structure and thermal properties of yttrium alumino-phosphate glasses.

The structure and thermal properties of yttrium alumino-phosphate glasses, of nominal composition (Y(2)O(3))(0.31-z)(Al(2)O(3))(z)(P(2)O(5))(0.69) with [Formula: see text], were studied by using a combination of neutron diffraction, (27)Al and (31)P magic angle spinning nuclear magnetic resonance, differential scanning calorimetry and thermal gravimetric analysis methods. The Vickers hardness of the glasses was also measured. The data are compared to those obtained for pseudo-binary Al(2)O(3)-P(2)O(5) glasses and the structure of all these materials is rationalized in terms of a generic model for vitreous phosphate materials in which Y(3+) and Al(3+) act as modifying cations that bind only to the terminal (non-bridging) oxygen atoms of PO(4) tetrahedra. The results are used to help elucidate the phenomenon of rare-earth clustering in phosphate glasses which can be reduced by substituting Al(3+) ions for rare-earth R(3+) ions at fixed modifier content.