الفهرس 
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Abstract
Barium ferrite in the present work has been prepared by mixing ferric oxide and barium carbonate of 99.9 purity in the powder form, with I : 1 molar ratio, and heat treated at temperature range from, 300° to 10000C, for 5 hour. The obtained phase or phases of barium ferrite were confirmed by using X-ray diffraction and Mossbauer
analysis.
The temperature dependence of electrical conduction for a mixture of Fe2O3 and BaCO3 with 1 : 1 mole ratio has been studied between room temperature and 3000C. The results show an attenuation in conductivity with increasing temperature which suggest protonic conduction at relatively low temperature range, where at higher range of temperature a small polaron jumping between Fe2+ and Fe3+ were occured. As the concentration of barium ferrite phases increases the
anomalous behaviour in a - 1/T diminishes.
Isothermal annealing studies for untreated and preheated samples were accomplished between room temperature and 3000C. The electrical conductivity, a , attenuates with increasing the time of annealing, t, to stationary values which is discussed according to the competition of generation and recombination of charge carriers.
The electrical conduction at high fields exhibits a quadratic dependence of current on the applied potential which predicts the formation of space charge. The mobility and concentration of charge
carriers are estimated and discussed for untreated and heat treated Fe203/BaCO3composites.
The ac conductivity, aae, dielectric constant, a’, and dielectric loss
, have been studied between room temperature and 3000C, in the frequency range (50 Hz - 100 KHz). At relatively low temperature range, an attenuation in a. , a’ and a” were occured with increasing in temperature which was attributed to the effect of
dehydration. While at higher temperature range, all these prameters increase with increasing temperature . Additionally , in the samples heat treated at 9000 and 10000C this anomalous behaviour
diminish
The frequency dependence of the ac conductivity show, in general, at lower range of frequency, that a increases slightly with increasing frequency, while at the higher range of frequency a strong dependence on frequency is recorded, as a result of the electron hopping between filled (Fe2+) and empty states (Fe3+).
dielectric loss decreases with
electronic, ionic, dipolar and for the abnormally values of the loss is discussed according to
The dielectric constant and increasing frequency arising from interfacial polarization. The reason
dielectric constant and dielectric interfacial effects.