Master curve generation and modeling of ac conductivity for Mn0.7+xZn0.3SixFe2-2xO4 spinel ferrite system

The compositional dependence of ac conductivity (sigma(ac)), real (sigma') and imaginary (sigma '') parts of complex electric conductivity (sigma*) was investigated as a function of temperature (T) and frequency (f) for Mn0.7+xZn0.3SixFe2-2xO4, x = 0: 0, 0.1, 0.2 and 0.3 spinel ferrite system. The compositional dependence of lattice constant values suggested that the most of the substituted Si4+- ions reside at grain boundaries and only a few Si-ions are inside grains. The variation of sigma(ac) (x, f, T) is explained on the basis of segregation and diffusion of Si4+ ions at grain boundaries and grains, respectively, and the electrode effect. Thermal variation of ac conductivity at fixed frequency suggested two different mechanisms which could be responsible for conduction in the system. It is found that sigma* is not the preferred presentation for dielectric data and the scaling process of real part of conductivity by normalized frequency and the scaled frequency were found unsuccessful. The fitting results of ac conductivity data with path percolation approximation were found suitable in low- frequency regime while in high- frequency regime, effective medium approximation (EMA) was found successful.