CONDUCTIVITY BEHAVIOR OF N-TYPE SEMICONDUCTING FERRITES FROM HYDROTHERMAL POWDERS

Authors
Citation
A. Dias et Rl. Moreira, CONDUCTIVITY BEHAVIOR OF N-TYPE SEMICONDUCTING FERRITES FROM HYDROTHERMAL POWDERS, Journal of materials research, 13(8), 1998, pp. 2190-2194
Citations number
18
Categorie Soggetti
Material Science
ISSN journal
08842914
Volume
13
Issue
8
Year of publication
1998
Pages
2190 - 2194
Database
ISI
SICI code
0884-2914(1998)13:8<2190:CBONSF>2.0.ZU;2-T
Abstract
The frequency and temperature dependencies of the dielectric permittiv ity and of the electrical conductivity of excess ferrous ions hydrothe rmal NiZn ferrites were analyzed before and after sintering. A decreas ing tendency with frequency of the dielectric responses was observed, but the high permittivities attained (epsilon' approximate to 10(5)) m asked any relaxation in these materials. This behavior is characterist ic of n-type semiconducting ferrites, where electron hopping between F e+2 and Fe+3 ions leads to very high conductivity values. The temperat ure 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 m axima, The electrical conductivity variations with temperature exhibit ed Arrhenius-type behaviors, with activation energies ranging from 0.3 4 eV (hydrothermal powder) to 0.16 eV (for the highest sintering tempe rature). These results were correlated to the variations in Fe+2 conce ntration and microstructure.