Structure and crystallization behavior of phosphorus-containing nepheline (NaAlSiO4) based sodium aluminosilicate glasses.

The study aims at understanding the structural role of P 2 O 5 in meta- and per-aluminous sodium aluminosilicate glasses, followed by its correlation with their crystallization behavior. Experimental results suggest an increase in the degree of polymerization of the phosphate network and a change in the aluminum environment in the glasses from Al(OSi) 4 to Al(OP) 4 with an increasing P 2 O 5 /SiO 2 ratio. The substitution of SiO 2 –by–P 2 O 5 in the amount varying between 10 – 20 mol.% suppresses the crystallization of nepheline. This has been attributed to the unavailability of Al3+ (to form Si–O–Al linkages) due to the formation of Al–O–P linkages in the glass structure. An increase in P 2 O 5 content (>20 mol.%) in peraluminous glasses results in the crystallization of AlPO 4 as the primary phase. The results have been discussed in the light of various models developed to predict the compositional dependence of nepheline crystallization in Hanford's high-level waste glasses. [ABSTRACT FROM AUTHOR]