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Conductivity behavior of n-type semiconducting ferrites from hydrothermal powders

Published online by Cambridge University Press:  31 January 2011

Anderson Dias  and
Roberto Luiz Moreira
Anderson Dias
Affiliation:
Departamento de Engenharia Metalúrgica e de Materiais, UFMG, 30160–030, Belo Horizonte, MG, Brazil
Roberto Luiz Moreira
Affiliation:
Departamento de Física, ICEx-UFMG, CP 702, 30123–970, Belo Horizonte, MG, Brazil
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Abstract

The frequency and temperature dependencies of the dielectric permittivity and of the electrical conductivity of excess ferrous ions hydrothermal NiZn ferrites were analyzed before and after sintering. A decreasing tendency with frequency of the dielectric responses was observed, but the high permittivities attained (ε′ ≈ 105) masked any relaxation in these materials. This behavior is characteristic of n-type semiconducting ferrites, where electron hopping between Fe+2 and Fe+3 ions leads to very high conductivity values. The temperature dependence of the dielectric permittivities revealed the existence of broader peaks. The electron hopping mechanism leads to a frequency dispersion of the temperature where the permittivities attain their maxima. The electrical conductivity variations with temperature exhibited Arrhenius-type behaviors, with activation energies ranging from 0.34 eV (hydrothermal powder) to 0.16 eV (for the highest sintering temperature). These results were correlated to the variations in Fe+2 concentration and microstructure.

Type
Articles
Information
Journal of Materials Research , Volume 13 , Issue 8 , August 1998 , pp. 2190 - 2194
Copyright
Copyright © Materials Research Society 1998

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References

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