On the Reaction Kinetics of Spinel-type Ferrite. I : Nickel Ferrite

概要

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The reaction kinetics of the formation of nickel ferrite was investigated by measuring the magnetic intensity which exhibits itself at various reaction temperatures in keeping other conditions constant, and the value of the experimental activation energies for formation of the spinel type ferromagnetic oxide was obtained from the temperature dependence upon a magnetic intensity representing the velocity of the progress in the reaction; thus the value of activation energy was found to be 44000 cal/mol and 25000 cal/mol for the dry and wet methods respectively. These values were compared respectively with those for ordinary solid reaction and for lattice defect in ionic crystal. Furthermore, the electrical conductivity of nickel ferrite under various heat treatments was measured and it was found that NiOFe_2O_3 shows considerably large electric resistivity, after heating at 1100℃ for 3 hours in the air. And, lastly, the relation between electrical conductivity and magnetic property was discussed on the basis of the theory of ferromagnetism for semiconductors.
東北大学の論文