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 | ν_Q | for ⁷Li and ²⁷Al are, respectively, 41±2 kc/sec and 284±6 kc/sec. On ²⁷Al sites with octahedral coordination, | ν_Q |=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 ν_Q 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.