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Electrical conductivity of pulverulent iron-cobalt molybdates Co 1−x Fe x MoO 4 : evidence for hopping conduction

Electrical conductivity of pulverulent iron-cobalt molybdates Co 1−x Fe x MoO 4 : evidence for... Abstract Different mixed iron-cobalt molybdates Co1−xFexMoO4 (0 < x ≤ 1) were prepared by means of a ceramic process. The influence of the isostructural substitution of Co2+ by Fe2+ and Fe3+ on the electrical conductivity of CoMoO4 was studied in the temperature range (50–600°C). The results show that the iron substitution increases the electrical conductivity and changes the conduction mechanism of CoMoO4. From a band conduction mechanism with an activation energy higher than 0.8 eV the conduction mode transforms into a hopping mechanism between the Fe2+ and Fe3+ ions in the octahedrally coordinated divalent cation sublattice. The activation energy is lower (0.4 eV) and does not alter around the polymorphic transition temperature. Owing to careful oxidations of the samples into cation deficient phases it was shown that the conductivity is proportional to the [Fe2+]/[Fe3+] ratio. These mild oxidations confirm the hopping mechanism. The presence of Co2+/Co3+ pairs has a minor contribution to the overall conductivity process. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Ionics Springer Journals

Electrical conductivity of pulverulent iron-cobalt molybdates Co 1−x Fe x MoO 4 : evidence for hopping conduction

Ionics , Volume 1 (4): 6 – Jul 1, 1995

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References (16)

Publisher
Springer Journals
Copyright
1995 IfI - Institute for Ionics
ISSN
0947-7047
eISSN
1862-0760
DOI
10.1007/BF02390211
Publisher site
See Article on Publisher Site

Abstract

Abstract Different mixed iron-cobalt molybdates Co1−xFexMoO4 (0 < x ≤ 1) were prepared by means of a ceramic process. The influence of the isostructural substitution of Co2+ by Fe2+ and Fe3+ on the electrical conductivity of CoMoO4 was studied in the temperature range (50–600°C). The results show that the iron substitution increases the electrical conductivity and changes the conduction mechanism of CoMoO4. From a band conduction mechanism with an activation energy higher than 0.8 eV the conduction mode transforms into a hopping mechanism between the Fe2+ and Fe3+ ions in the octahedrally coordinated divalent cation sublattice. The activation energy is lower (0.4 eV) and does not alter around the polymorphic transition temperature. Owing to careful oxidations of the samples into cation deficient phases it was shown that the conductivity is proportional to the [Fe2+]/[Fe3+] ratio. These mild oxidations confirm the hopping mechanism. The presence of Co2+/Co3+ pairs has a minor contribution to the overall conductivity process.

Journal

IonicsSpringer Journals

Published: Jul 1, 1995

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