Tunable permeability and permittivity of low loss NiZnCo ferrite by sintering temperature for VHF-UHF applications

Summary form only given. In this paper, by modifying the sintering temperature (TS), tunable permeability and permittivity are achieved in NiZnCo ferrite over a wide frequency range. The crystal phase, densification and microstructure of the NiZnCo samples were analyzed to correlate with the variations of the magnetic and dielectric properties. A series of spinel NiZnCo ferrites with nominal composition Ni
_0.5
Zn
_0.3
Co
_0.2
Fe
₂
O
₄
were prepared by solid-state reaction method. The samples were sintered in the temperature range of T
_S
=950°C-1150°C in oxygen gas atmosphere in order to explore the NiZnCo ferrite with matching permeability and permittivity as well as low losses. The phase compositions of the sintering samples were determined by X-ray diffraction (XRD) using Cu Kα radiation at room temperature. The XRD results indicate that all the samples show the formation of single phase cubic spinel structure without any signature of secondary phase. The microstructures of the samples were examined by scanning electron microscope (SEM). It was found that the average grain size and densification were obviously enhanced with increasing sintering temperature. The effects of sintering temperature TS on the magnetic and dielectric properties were systematically investigated. The complex permeability and permittivity spectra, as well as magnetic and dielectric losses of the samples were measured in 10 MHz-1 GHz.