NMR study of sodium ion motion and distribution in beta-alumina

Abstract

NMR studies of 23Na in single crystal beta-alumina have been made which include (1) investigation of the quadrupole induced shifts of the 1/2↔−1/2 magnetic transition at 77 and 103 K, and (2) measurement of the width of the 23Na-NMR line as a function of temperature for several crystal orientations. The low temperature rotation patterns show that sodium ions occupy several independent sites in the lattice. At temperatures above about 110 K, the jumping of sodium ions among these several sites is manifested by motional narrowing of the quadrupolar spectrum. At these higher temperatures, a single, symmetric resonance line is observed. Analysis of the narrowing of this resonance line with increasing temperature yields an activation energy of 0.1 eV.