Temperature tailored magneto-dielectric properties of Cd-substituting Mg-based ferrite ceramics for miniaturized VHF antennas

Abstract

The microstructure formation and structural regulation of Mg-Cd ferrites (Cd0.15Mg0.85Fe2O4) with 5% Bi2O3 addition at different sintering temperatures (880, 900, 920, and 940 °C) werer invsetigated for application in VHF antennas. The changes including microstructure, phase composition, magnetic and dielectric properties were mainly characterized. It was found that increasing temperature resulted in superior microstructure with accrescent grain size and denser arrangement. XRD patterns revealed normal spinel phase and a secondary phase of Bi compound. Meanwhile, a reinforcement of the magnetization including increased saturation magnetization (from 37.8 to 46.6 emu/g) and dropped coercivity (from 98.2 to 65.9 Oe) were obtained through hysteresis loops. A slight increment of μ' and ' were measured over a broad frequency range in VHF bands. Therefore, excellent magneto-dielectric properties of the proposed ferrites were obtained. In addition, low magnetic losses (tan δμ ~10 -2) and dielectric losses (tan δμ ~10 -3) indicating low power loss in operation. It is foreseeable that these properties of the proposed ferrites would behave well in miniaturized VHF antennas.