Impedance spectroscopy studies on polycrystalline BiFeO3 thin films on Pt/Si substrates

In this paper, we report on the results of temperature dependent impedance measurements on chemical solution deposited BiFeO3 thin films on Pt/Si substrates. X-ray diffraction analysis showed the presence of predominately single phase BiFeO3. The measurements were made in the frequency range of 100-10(7) Hz and between 27 and 250 degrees C. Plots between real and imaginary parts of impedance (Z(') and Z(')) and electrical modulus (M-' and M-') in the above frequency and temperature domain suggest the presence of two relaxation regimes which are attributed to bulk and grain boundary responses. Below 150 degrees C, both conductivity and real dielectric constant show a steplike behavior. The frequency independent regions in 10-100 kHz indicate relaxation of the bulk conduction, while at lower frequency there is a strong frequency dependence associated with the dispersion toward relaxation of the grain boundary. In contrast, at and above 150 degrees C, frequency independent behavior of dc conduction becomes dominant. The bulk dielectric constant was estimated as similar to 225, which is close to the values reported in the literature. Estimated grain and grain boundary conductivity activation energies are 0.28 and 0.81 eV, respectively.