93Nb NMR Linewidths in Nonstoichiometric Lithium Niobate

Abstract

The angle variation of the 93Nb NMR linewidths is obtained for an off-stoichiometry lithium niobate crystal. It is shown that the widths can be calculated on the basis of a model in which both the magnitude and direction of the electric field gradient are treated as random quantities. A second type of niobium, with a near zero quadrupole coupling constant, is shown to exist in off-stoichiometric crystals. This amounts to roughly 6% of the total niobiums. This new resonance is undoubtedly associated with the mechanism of charge compensation and suggests that the excess niobium substitutes for lithium.