Low temperature firing of Co2Y–NiCuZn ferrite composites

Hexagonal structure magnetoplumbite ferrites have revealed a higher dispersion frequency than that of nickel ferrites because of the magnetoplumbiteʹs magnetic anisotropy. The magnetoplumbite ferrite densification temperature always exceeds 1000 °C and the initial low temperature firing permeability of magnetoplumbite ferrites with added glass is too low (μi = 2–4). Therefore, it is desirable to develop a material that has a higher permeability at above 300 MHz and can be densified at temperatures below 900 °C. The Bi2O3–B2O3–ZnO–SiO2 (BBSZ) glass addition effects on the densification and magnetic properties of Co2Y–NiCuZn ferrite composites with various Co2Y/NiCuZn ferrite ratios were investigated. The densification of Co2Y–NiCuZn ferrite composites was enhanced by the addition of glass at low sintering temperatures (<900 °C) due to the liquid phase sintering. Co2Y–NiCuZn ferrite composites with 4 wt% BBSZ glass sintered at 900 °C show a relative density above 90%, a high-initial-permeability of 5–6, a quality factor of above 30 in the 200–300 MHz frequency and a resonance frequency above 1 GHz, which can be used in high frequency multilayer chip inductors.