27Al and 29Si MAS NMR investigations of cordierite glass, mu- and alpha-cordierite.

27Al and 29Si Magic-Angle Spinning NMR results are reported for conventionally prepared glass of cordierite stoichiometry (2MgO.2Al2O3.5SiO2), the metastable high-quartz solid solution (mu-cordierite) and the high-temperature polymorph of cordierite (alpha-cordierite). Both, 27Al two-dimensional (2D) quadrupole nutation experiments and 27Al satellite transition spectroscopy (SATRAS) have been applied to identify two different tetrahedrally-coordinated aluminium sites (AlO4). SATRAS has been used to extract the quadrupole interaction parameters and their distribution, the isotropic chemical shifts and the relative populations of the different Al sites. Both, the 27Al and 29Si NMR results, lead to the conclusion that a perfect Si/Al disorder does not exist in these investigated cordierite samples.