Solid-State 31P/27Al and 31P/23Na TRAPDOR NMR Investigations of the Phosphorus Environments in Sodium Aluminophosphate Glasses

Solid-state 31 P/ 27 Al and 31 P/ 23 Na TRAPDOR NMR experiments have been used to investigate the spatial distribution of aluminum and sodium cations with respect to the phosphate backbone for a series of sodium aluminophosphate glasses, x Al 2 O 3 ·50Na 2 O· (50− x )P 2 O 5 (0 ≤ x ≤ 17.5). From the 31 P/ 27 Al and 31 P/ 23 Na TRAPDOR data gathered, information about the medium-range order in these glasses was obtained. The expanded data allow for better identification and interpretation of the new resonances observed in the 31 P MAS NMR spectra with the addition of aluminum. The results of these experiments show that the sodium phosphate distribution remains relatively unchanged for the glass series and that the addition of aluminum occurs primarily through the modification of the phosphate tetrahedral backbone in the melt.