AL-27 AND SI-29 MAS NMR INVESTIGATIONS OF CORDIERITE GLASS, MU-CORDIERITE AND ALPHA-CORDIERITE

Al-27 and Si-29 Magic-Angle Spinning NMR results are reported for conv entionally prepared glass of cordierite stoichiometry (2MgO . 2Al(2)O( 3) . 5SiO(2)), the metastable high-quartz solid solution( mu-cordierit e) and the high-temperature polymorph of cordierite (alpha-cordierite) Both, Al-27 two-dimensional (2D) quadrupole nutation experiments and Al-27 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 paramete rs and their distribution, the isotropic chemical shifts and the relat ive populations of the different Al sites. Both, the Al-27 and Si-29 N MR results, lead to the conclusion that a perfect Si/Al disorder does not exist in these investigated cordierite samples. (C) 1997 Elsevier Science B.V.