Impedance spectroscopic characterization of fine-grained magnetoelectric Pb(Zr0.53Ti0.47)O3-(Ni0.5Zn0.5)Fe2O4 ceramic composites

Temperature dependent impedance spectroscopic analysis of fine-grained magnetoelectric Pb(Zr0.53Ti0.47)O-3-(Ni0.5Zn0.5)Fe2O4 (PZT-NZFO) composites was investigated. Debye-like impedance relaxation peaks were observed at intermediate frequency range. Maxwell-Wagner (MW) relaxation model was used to explain the space charge effect due to heterogeneous PZT and NZFO grain boundary in finer structure. The total resistivity was dominated by the grain boundary resistance due to the blocking effect arisen from the glass phase additive. The small value of conductivity measured in this system suggested the glass additive markedly modified the grain boundary properties. Electric modulus spectra reflected the contributions from two different effects: the large resolved semicircle arc was caused by the grain effect and the small poorly resolved semicircle arc was attributed to the grain boundary. The activation energy calculated from the impedance spectra was consistent with value estimated from the modulus spectra. Investigation on dielectric spectra revealed a polydispersive dielectric relaxation existing in the system, which was also demonstrated in the ac conductivity spectra. Small polaron relaxation and MW-type polarization mechanism were discussed through the analysis on the ac conductivity spectra. (C) 2011 Elsevier B.V. All rights reserved.