Nuclear magnetic resonance investigations of aluminum containing phosphate glass-ceramics

Abstract Glasses and glass-ceramics of the system P 2 O 5 –CaO–Na 2 O–{Al 2 O 3 } have been studied by 31 P and 27 Al 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. 27 Al correlation experiments do not detect the presence of Al–O–Al bonds in the glasses and in the glass-ceramics.