Impedance spectroscopy and magnetic studies on Co2Z ferrite sintered with SiO2 and Bi2O3 additives

Z-type (Ba3Co2Fe24O41) ferrites with Bi2O3 and SiO2 additives were prepared by solid-state reaction method. The electrical transport properties were systematically investigated and analyzed by impedance spectroscopy in the frequency range of 1 Hz to 1 MHz at different temperatures. The peak broadening in real and imaginary part of impedance spectra demonstrates the existence of multiple relaxations. Two distinct slopes of relaxation time observed represent the deviation from non-Debye type relaxation. Partially overlapped scaling behavior illustrated that the dynamic process of charge carriers was temperature dependent. The additives got segregated along the grain boundaries and exhibit their own resistance, which is verified by fitting of the Nyquist plots. This relaxation process was explained on the basis of Maxwell-Wagner effect with three heterogeneous dielectric media (grain, grain boundary and additive layer). The translatory motion of dynamic charge carriers and lattice ions is governed by small and large polaron hopping in the material. The saturation magnetization of Co(2)Z-Si is higher compared to Co(2)Z-P and Co(2)Z-Bi samples, due to formation of minor M-type phase.