Co-substituted LiZnTiBi ferrite with equivalent permeability and permittivity for high-frequency miniaturized antenna application

Abstract

Abstract In the present work, a Co-substituted LiZnTiBi (Li0.43Zn0.27CoxTi0.13Fe2.167-xBi0.003O4) ferrite with equivalent permeability and permittivity was prepared by a low-temperature sintering method. In detail, the LiZnTiBi ferrite with high permeability was obtained by a solid phase method. Next, different mass of Co2O3 (x = 0.100, 0.125, 0.150, 0.175 and 0.200) were added to reduce permeability (μr’) and enhance cut-off frequency (fr) of the ferrite. Results indicated that the Co-substituted LiZnTiBi ferrite with equivalent permeability and permittivity (μr’ = er’ = ∼12.3) was obtained when additive amount of Co2O3 (x) is around 0.150. Meanwhile, the cut-off frequency (fr) of the ferrite is more than 500 MHz. Also, the influences of Co2O3 additive on the microstructure and phase structure of the LiZnTiBi ferrite have been investigated and discussed. SEM images indicated that the Co-substituted LiZnTiBi ferrites possess uniform and compact grains (average grain size is ∼1 μm). XRD patterns demonstrated that the LiZnTiBi ferrite material has a pure spinel structure. Rietveld refinement of XRD proved that Fe3+ is substituted by Co3+. And energy dispersive spectrometer (EDS) result indicated that the Co element is existed in ferrite grains. Such a low-temperature sintering ferrite substrate material with equivalent permeability and permittivity at high frequency (@500 MHz) should also be an alternative material for microwave devices, especially for miniature antenna.