Solid-state 27Al and 29Si NMR investigations on Si-substituted hydrogarnets

Partially deuterated Ca3Al2(SiO4)3−x(OH)4x hydrates prepared by a reaction in the presence of D2O of synthetic tricalcium aluminate with different amounts of amorphous silica were characterized by 29Si and 27Al magic-angle spinning nuclear magnetic resonance (NMR) spectroscopy. The 29Si NMR spectroscopy was used for quantifying the non-reacted silica and the resulting hydrated products. The incorporation of Si into Ca3Al2(SiO4)3−x(OH)4x was followed by 27Al NMR spectroscopy: Si:OH ratios were determined quantitatively from octahedral Al signals ascribed to Al(OH)6 and Al(OSi)(OH)5 environments. The NMR data obtained were consistent with the concentrations of the Al and Si species deduced from transmission electron microscopy energy-dispersive spectrometry and Rietveld analysis of both X-ray and neutron diffraction data.