Conduction mechanisms and dielectric constant features of Fe doped ZnO nanocrystals

Fe doped ZnO nanocrystals (NCs) were synthesized from low cost sol gel method and the effect of iron content on their structural, transport and dielectric properties was studied. X-ray diffraction (XRD) measurements exhibit good crystalline quality of all the prepared NCs and a reduction of the crystallite size with Fe doping. Raman spectra confirmed the good crystallinity and revealed the formation of ferric phases for highly doped samples. Investigations of the impedance characteristics indicate that the samples are perfectly modulated from equivalent circuits using a constant phase element (CPE). Analysis of complex impedance and electrical modulus revealed a relaxation process dependent on temperature and of non-Debye type. Single activation energy was estimated for the electronic conduction, based on the Arrhenius plots. The conduction mechanism was governed from small polaron hopping in all the ZnO:Fe materials. The frequency dependence of the electric conductivity followed a simple Jonscher power behavior sigma ac(omega) = sigma dc + A omega s (0.5< s < 1), where the exponent s increased with temperature. The dielectric measurements, in both medium and high frequency regions, exhibited high dielectric constant values and low dielectric losses for all the samples, which could favor the use of Fe doped ZnO a as promising candidate for energy storage. The electrical modulus provides double relaxation times with low values. All the properties indicate that the ZnO:Fe material is suitable for device applications.