Nuclear magnetic resonance investigations of aluminum containing phosphate glass-ceramics

Glasses and glass-ceramics of the system P2O5-CaO-Na2O-{Al2O3} have been studied by P-31 and Al-27 and two-dimensional correlation nuclear magnetic resonance. The basic glasses have a chain-like structure including amorphous diphosphate and longer chains having at least four units. The Q(1)/Q(2) group ratios depend on both the content of network-modifying oxides and aluminum oxide. Crystallization of the glasses involves the conversion of glassy metaphosphate sites into crystalline pyro- and orthophosphate sites. Al-27 correlation experiments do not detect the presence of Al-O-Al bonds in the glasses and in the glass-ceramics. (C) 2000 Elsevier Science B.V. All rights reserved.