Nuclear Magnetic Resonance Determination of Some Microscopic Parameters of LiAl5O8

Abstract

Quadrupole coupling data have been obtained from analysis of NMR spectra of 7Li and 27Al in single crystal and polycrystalline ordered LiAl5O8. On axially symmetric sites, values of | νQ | for 7Li and 27Al are, respectively, 41±2 kc/sec and 284±6 kc/sec. On 27Al sites with octahedral coordination, | νQ |=683±25 kc/sec, η=0.347±0.025, and the orientation of principal axes has been found. An ionic model calculation gives estimates of distortions of the crystal from the ideal spinel form and possible signs for the νQ values. A convenient general expression for second-order shifts is given, together with results for the positions of the prominent second-order features in the line shapes of polycrystalline samples.