P-31 MAGIC-ANGLE-SPINNING NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY OF CALCIUM-PHOSPHATE GLASSES

P-31 Magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy of a series of Ca phosphate glasses yields the following results and conclusions: (1) The relative concentrations of Q1, Q2, and Q3 P-tetrahedra are consistent with theoretical expectation and previous experimental work, except that near the metaphosphate composition tetrahedra with all three polymerizations are present. This increased range of polymerizations is consistent with previous work on silicate compositions. (2) The chemical shift of P-31 pin Q2 polymerization becomes less shielded (less negative) with increasing Ca content, parallelling the previously published results for Na phosphate glasses. (3) The chemical shifts are systematically more negative than for the Na phosphate glasses, consistent with theoretical expectation and experimental work.