109Ag NMR and relaxation mechanism in single crystal Ag β-alumina

Abstract

Temperature dependence of 109Ag NMR spectrum and spin-lattice relaxation T 1 was measured for a single crystal of Ag β-alumina (Ag 1.17Al 11O 17.09) at external magnetic field of 4.7 T (9.3 MHz) and 9.4 T (18.6 MHz). Only a single spectrum peak is observed at room temperature, it reflects fast site exchange of Ag ions. The chemical shift of the peak position depends on the angle between c-axis and external field B 0. From the angle dependence, the values of screening tensor are determined to be, σ xx PAS = σ yy PAS = − 54.7 ppm, σ zz PAS = − 212 ppm. The large difference between σ zz PAS and σ xx PAS indicates a strong interaction between Ag and surrounding oxygen. The relaxation mechanism is discussed using the Scalar Coupling (SC) model and Screening Tensor Fluctuation (STF) model. The field dependence of the T 1 observed at 4.7 T and 9.4 T strongly supports the SC model. It suggests that there are strong correlations between Ag ions in β-alumina and it probably plays an important role to the high ionic conductivity.