Impedance spectroscopy and conductivity mechanism of CoFe₂O ₄-Pb(Zr_0.53Ti_0.47)O₃ composite thick films

In the present work, the impedance spectroscopy and conductivity mechanism of multiferroic CoFe₂O₄-Pb(Zr_0.53Ti _0.47)O₃ composite thick films have been investigated. Temperature dependent impedance spectroscopy analysis was conducted in the temperature range of 25-275 °C with the frequency ranging from 100 Hz to 1 MHz. Two impedance relaxation peaks were observed at high frequency with low temperature, and low frequency with high temperature. These peaks were attributed to grain and grain boundary effect, respectively. Electric modulus spectra clearly presented the contributions from both effects in terms of remarkably semicircle arcs. Two different grain boundary effects were reflected in the electric modulus spectra: one caused by homogeneous PZT grain boundary and the other due to the heterogeneous CFO and PZT grain boundary. The activation energy calculated from modulus spectra was consistent with the estimated value from impedance spectra. Investigation on dielectric spectra revealed a dc conductivity region and two nearly constant loss regions, corresponding to the grain effect and two different grain boundary effects, which were also demonstrated in ac conductivity spectra. Furthermore, ion hopping and transport mechanism were unveiled through the analysis on ac conductivity spectra.