摘要
Frequency-dependent dielectric constant,dielectric loss,AC conductivity values and complex impedance spectra of V_(2)O_(5)-added Ni-Co-Zn ferrites(Ni_(0.62)Co_(0.03)Zn_(0.35)Fe_(2)O_(4)+xV_(2)O_(5),where x=0,0.5,1 and 1.5 wt.%)have been investigated at room tempera-ture.The dielectric properties of the samples follow the Maxwell-Wagner polarization model.An inverse relationship was found between dielectric constant and AC electrical resistivity for all the samples.The dielectric constants decreased with the addition of V_(2)O_(5),while the electrical resistivities of V_(2)O_(5)-added Ni-Co-Zn ferrites are found to be larger than that of pure Ni-Co-Zn ferrite.The AC conductivity was reduced with the addition of V_(2)O_(5)to Ni-Co-Zn ferrite at lower-frequency region.However,AC conductivity shows a sharp increase at higher-frequency region,which could be attributed to the enhancement of electron hopping between the Fe2+and Fe3+ions in the ferrite matrix due to the activity of the grains.The complex impedance spectroscopy results through Cole-Cole/Nyquist plot have demonstrated a single semicircular arc.It indicates that conduction mechanism takes place predominantly through the grain/bulk property,which could be ascribed to the larger grain size of V_(2)O_(5)-added Ni-Co-Zn ferrites.
