Low temperature sintered magneto-dielectric ferrite ceramics with near net-shape derived from high-energy milled powders

Abstract

Nanosized Ni0.70Zn0.25Co0.05Fe1.90Mn0.02O4 ferrite ceramics were fabricated from high-energy ball milled powder mixtures with various ratios of Fe2O3/Fe as starting materials, in order to achieve magneto-dielectric materials with near net shape behavior for practical applications. The ferrite ceramics were obtained by sintering the milled powder compacts at 800 °C for 4 h, with a linear expansion of less than 4% as compared to the green pellets. The ceramics had an average grain size of less than 200 nm. The real part of relative permittivity decreases with increasing percentage of Fe2O3 used in the starting mixtures. The sample from the powder mixture with 50% Fe2O3 exhibits promising magneto-dielectric properties at frequencies of up to 90 MHz, which can be used for miniaturization of antennas at very high frequency (VHF) band.