Nonlinear and linear impedance of bismuth vanadate ceramics and its relation to structural properties

The nonlinear and linear electrical properties, topography, and microstructure of bismuth-vanadate ceramics, were studied. The structure was observed with the use of X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and confocal microscopy methods. The obtained results showed that ceramic is porous. Two phase transitions were determined with the use of DSC measurements. The linear and nonlinear ac complex conductivity was studied as the function of frequency, temperature, and ac voltage. The activation energy of dc conduction processes was evaluated. The temperature dependence of conductance and permittivity showed a specific behaviour in two temperatures which were in agreement with phase transition temperatures. The nonlinear impedance studies showed that the ratio of third harmonic to base frequency conductivity reached more than 0.20. Obtained nonlinearities achieved two maxima near phase transition temperatures.