Trivalent Iron Ion Substituted Co₂Z Hexagonal Ferrites for Ultra High Frequency Applications

Abstract

Z-type hexagonal ferrites for ultra high frequency of gigahertz range were prepared by substitution of trivalent iron ions for various metal ions. Thereby improving a sintering process and the addition of lwt.% BaCO₃ to calcined powder, single-phase Z-type ferrite was obtained even when we used the conventional ceramic techniques. Initial permeability of Z-type ferrites with composition of Ba₃Co₂Cu_x/2Si_x/2Fe_24-xO₄₁ (X=0) was 17.8 which was sufficiently larger than the value previously reported. Moreover, the limit of frequency was 0.635GHz which was as large as previously reported value. In spite of low bulk density (4.28g/cm³), initial permeability of Z-type ferrites with composition of Ba₃Co₂Cu_x/2Si_x/2Fe_24-xO₄₁ (X=1) was 9.51 and the limit of frequency was 1.5GHz which were useful and practical values as magnetic materials for ultra high frequency. When the amount of substitutional metal ions increased, initial permeability and resonance frequency were decreased. In substitution by Cu²⁺ ion and Nbs⁵⁺ ion, initial permeability of Z-type ferrite with composition of Ba₃Co₂Cu_2X/3Nb_X/3Fe_24-XO₄₁ (X=1) was 8.1 and the limit of frequency was 1.2GHz which was less than the values of Ba₃Co₂Cu_X/2Si_X/2Fe_24-XO₄₁ (X=0, 1). Quantitative and qualitative analysis indicated that various substitutions have led to the formation of two hexagonal structures.