Determination of the aluminium coordination in aluminium-oxygen compounds by solid-state high-resolution 27AI NMR
Abstract
High-resolution 27AI NMR spectra of polycrystalline aluminates have been studied at 70.4 MHz. Magic-angle spinning was used to reduce quadrupole effects and dipolar interaction. The isotropic 27AI chemical shifts depend mainly on the AI—O coordination For AI—O tetrahedra shifts of 55 to 80 ppm. were measured in contrast to those of AI—O octahedra at 0 ppm.
References (14)
- P. Tarte
Spectrochim. Acta.
(1967) - E.W. White et al.
Am. Mineralogist
(1969) - A.H. Silver et al.
J. Chem. Phys.
(1958) - D. Müller et al.
Z. Chem.
(1977) - J.W. Akitt et al.
J. Chem. Soc. Dalton
(1972) - H.-J. Behrens(1980)
- W. Gessner(1979)
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