Impedance Spectroscopy Study of Li Ion Dynamics in Single Crystal, Microcrystalline, Nanocrystalline, and Amorphous LiNbO3

Impedance spectroscopy was employed to investigate the Li ion diffusivity in single crystal, microcrystalline, nanocrystalline and amorphous lithium niobate (LiNbO3). Nanocrystalline LiNbO3 with different grain sizes was prepared by high-energy ball milling from the microcrystalline starting material. The amorphous form was prepared by a double alkoxide (sol-gel) route. The frequency dependent conductivity was measured under oxygen atmosphere at frequencies, omega�/2pi, ranging from 5 Hz to 13 MHz. The ionic conductivity at, e.g., 450 K was found to increase by about seven orders of magnitude by going from the single crystal through the microcrystalline to the corresponding nanocrystalline and amorphous forms. The increased free volume in the amorphous material could be responsible for the enhanced conductivity, whereas in nanocrystalline LiNbO3 the behavior is governed by the increased fraction of the interfacial regions which are highly disordered and may in the present case be visualized as amorphous. In all cases the frequency dependence of the real part of the conductivity can be represented by a power law and can be scaled to give master curves. Impedance data were analyzed in the complex plane plot (with (omega) as implicit parameter). Both the dc conductivity and the relaxation frequency of the impedance arc, (omega)r/2�, were found to follow Arrhenius behavior with similar activation energies Impedance Spectroscopy Study of Li Ion Dynamics in Single Crystal, Microcrystalline, Nanocrystalline and Amorphous LiNbO 3. Available from: https://www.researchgate.net/publication/250354649_Impedance_Spectroscopy_Study_of_Li_Ion_Dynamics_in_Single_Crystal_Microcrystalline_Nanocrystalline_and_Amorphous_LiNbO_3 [accessed Jun 12, 2017].