Rietveld refinement of X-ray diffraction, impedance spectroscopy and dielectric relaxation of Li-doped ZnO-sprayed thin films

In this paper, thin films of lithium-doped zinc oxide (ZnO: Li) were prepared by spray pyrolysis in a monophase hexagonal wurtzite structure as shown by X-ray analysis. Rietveld refinement of the X-ray diffraction diagram was applied to calculate the crystalline structure parameters. Impedance spectroscopy, electrical conductivity and dielectric measurements, at various temperatures 340–440 °C and in a frequency spectrum from 5 Hz to 1 MHz, were performed using the EC-Lab V10.12 system. During the electrical conduction processes in the sample, the physical parameters of ZnO:Li thin films such as dielectric constant, relaxation frequency and electrical conductivity σ_ac and σ_dc, were examined. In addition, AC conductivity analysis resulted in a power law (σ_ac = ω^s). Obviously, the temperature dependence of the exponent s fitted well with the correlated barrier hopping (CBH) model proposed by Elliott. Finally, the dependence of conductivity and dielectric constants with frequency and temperature was discussed.