Solid state NMR study supporting the lithium vacancy defect model in congruent lithium niobate
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93Nb and 7Li wideline- as well as MAS-NMR measurements were performed on powdered and single crystal lithium niobate of defective congruent composition (48.4% Li2O; 51.6% Nb2O5) using a magnetic field strength of 7.05 Tesla with the aim to distinguish between a lithium vacancy defect model (1% of the Nb atoms in a different site) and a niobium vacancy defect model (5% of the Nb atoms in a different site). Although the line width of the 7Li signal of powdered lithium niobate could be reduced to 0.6 kHz by using MAS-NMR with a rotational frequency of 4000 Hz, there was no second 7Li signal apparent, indicating different chemical surroundings for 7Li nuclei caused by the defect structure. The wideline spectra of 93Nb NMR measurements on lithium niobate single crystals in various orientations do not exhibit a second resonance and therefore contradict several earlier 93Nb NMR studies from which a niobium defect model was substantiated. Additionally, earlier NMR measurements could be explained on the basis of the complex 93Nb MAS spectra of powdered material. © 1994.
author list (cited authors)
Blümel, J., Born, E., & Metzger, T. h.