Zn- and Cu-substituted Co2Y hexagonal ferrites: Sintering behavior and permeability

Abstract

Y-type polycrystalline hexagonal ferrites Ba2Co2−x−yZnxCuyFe12O22 with 0≤x≤2 and 0≤y≤0.8 were prepared by the mixed-oxide route. Single phase Y-type ferrite powders were obtained after calcinations at 1000°C. Samples sintered at 1200°C show a permeability that increases with the substitution of Zn for Co and display maximum permeability of μ′=35 at 1MHz for x=1.6 and y=0.4. A resonance frequency fr=500MHz is observed for Zn-rich ferrites with y=0 and 0.4. The saturation magnetization increases with substitution of Zn for Co. Addition of Bi2O3 shifts the temperature of maximum shrinkage down to T≤950°C. Moreover, an increase of the Cu-concentration further lowers the sintering temperature to T≤900°C, enabling co-firing of the ferrites with Ag metallization for multilayer technologies. However, low-temperature firing reduces the permeability to μ′=10 and the resonance frequency is shifted to 1GHz. Thus substituted hexagonal Y-type ferrites can be used as soft magnetic materials for multilayer inductors for high frequency applications.