Portal de Periódicos da CAPES

Aluminum-27 NMR study of AIP04-21 and andalusite. Advantages of high-field and very fast MAS

1988; Elsevier BV; Volume: 80; Issue: 3 Linguagem: Inglês

10.1016/0022-2364(88)90239-9

1557-8968

Lawrence B. Alemany, Hye Ja Kyung, C Timken, Ivy D. Johnson,

Solid-state spectroscopy and crystallography

High-field (11.7 T) 21Al NMR spectra of the aluminophosphate AIP04-21 and the mineral andalusite obtained with magic-angle spinning (MAS) at up to 15 kHz are reported. Such rapid spinning compared to conventional MAS at <5 kHz can result in considerable spectral simplification by moving the spinning sidebands outside the region containing the centerbands. For AIP04-21, which contains appreciably distorted A104 and A105 groups, high-speed spinning provides a spectrum with well-defined centerbands that allow the quadrupole coupling constant e2gQ/h, the asymmetry parameter η and the isotropic chemical shift δiso to be estimated for the 27Al nucleus in each group. For andalusite, MAS at 15 kHz is still inadequate for obtaining an unambiguous spectrum of the highly distorted A106 species due to its very large e2gQ/h (15.6 MHz). In contrast, the less highly distorted A105 species (ezgQ/h = 5.9 MHz) gives a strong centerband exhibiting the expected second-order quadrupolar lineshape.