OBSERVATION AND ACCURATE QUANTIFICATION OF AL-27 MAS NMR-SPECTRA OF SOME AL2SIO5 POLYMORPHS CONTAINING SITES WITH LARGE QUADRUPOLE INTERACTIONS

Al-27 MAS NMR spectra from two polymorphs of Al2SiO5, kyanite and andalusite, are presented. Unambiguous extraction of quadrupole interactions of up to 15.5 MHz (= C(q) = e2qQ/h) are possible from fast MAS (> 18 kHz) NMR spectra obtained at an applied magnetic field of 11.7 T. It is shown from a knowledge of the magnitude of C(q) combined with some recently introduced analysis that correction of the integrated intensity of the centreband to reflect accurately the aluminium distribution in these samples is possible.