7Li NMR study of milling effects on instability of lithium-sites in lithium substituted silver niobate

Abstract

Site occupation and structural change in Li substituted AgNbO 3 were probed by 7 Li NMR. Characteristic changes in the 7 Li NMR spectra depending on Li content were observed. Analysis of integrated intensity of the spectra revealed that 16 % of substituted Li + ions occupy quasi-stable sites induced in crystal structure at 300 K in the 5 mol.% Li substituted sample and would be in the state of motion, which are comparable to that of Li + ion in LiNbO 3 at high temperature. On the other hand, it was found that the Li + /Ag + sublattice in the 12.5 mol.% Li substituted sample is easily made unstable by structural disturbance introduced in structure and instability of the sublattice stimulates a local Li + ion motion via quasi-stable sites at room temperature. An appearance of the quasi-stable sites in local structure due to the Li substitution is closely related to instability of the Li/Ag sublattice and Li + ion dynamics in Li substituted AgNbO 3 .