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Advances in Materials Science and Engineering
Volume 2016, Article ID 1934783, 7 pages
Research Article

Microstructure and Electromagnetic Properties of Ni-Zn-Co Ferrite up to 20 GHz

1Laboratory of Materials for Electrotechnics, Department of Electrical and Computer Engineering, Aristotle University, 54124 Thessaloniki, Greece
2Laboratory of Inorganic Materials, Centre for Research and Technology Hellas, Thermi, 57001 Thessaloniki, Greece

Received 3 January 2016; Accepted 31 March 2016

Academic Editor: Joke Hadermann

Copyright © 2016 Charalampos Stergiou. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The present paper examines the relation between different developed microstructures and the microwave electromagnetic properties in Ni-Zn-Co ferrite. To this end, the Ni0.25Zn0.25Co0.5Fe2O4 composition has been prepared with the conventional ceramic process with varied prefiring (750°C, 1000°C) and sintering top temperatures (1200°C, 1250°C). When lower temperatures are applied in these production stages, incomplete microstructures with low density, higher porosity, or finer grains are achieved. On account of these features, the contributions of domain wall motion and spin rotation to the complex permeability move to higher frequencies, whereas microwave dielectric permittivity is decreased. In particular in conjunction with the high Co content, the wall relaxation and spin resonance are interestingly forced to occur at 850 MHz and 8.05 GHz, respectively. Regarding the electromagnetic wave attenuation, the ferrite annealed at lower temperatures exhibits strong return loss peaks at higher frequencies, but without other performance improvement. We should notice that the variations in sintering temperature yield the maximum changes in the recorded parameters, including the coercive field, and , indicating the inferior role of prefiring in Ni-Zn ferrite.