M. R. Eraky
Total AC conductivity, , of Co-Ti substituted SrCaM hexaferrite, with the chemical formula Ca0.5Sr0.5CoxTixFe12-2xO19(where 0.0≤x≤0.8) has been studied in the frequency range from 100Hz to 1MHz and in the temperature range from 305 to 600K. It is noticed that increases with frequency and temperature, which reveals the semi-conductive behavior of the samples. The value of conductivity at high temperature region has been discussed in terms of hopping of the small polarons and multiple hopping processes of the localized charge carriers. The measurements reveal that at moderate and low temperatures the conduction mechanism depend on the classical barrier hopping (CBH) of localized charge carriers. Experimentally, we have detected semiconductor/metal transition temperatures of the samples with 0.2≤x≤0.6 at high temperatures and high frequencies. The semiconductor/metal phenomenon can be used in sensors and switching applications. It is shown that the value of the total conductivity increases with doping parameter, x, and reach to the maximum for the sample with x=0.4 after that decreases. This behavior was related to the decreasing in the porosity and increases of hopping electrons and holes between Fe3+ -Fe2+ and Co2+- Co3+up to x =0.4. The increasing in porosity and the increasing in hopping length causes obstruct in hopping process and decreases the total conductivity for the samples with 0.4
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