High-frequency properties of Si-doped Z-type hexaferrites

In order to improve the high-frequency electromagnetic properties of (Co0.4Zn0.6)2Z hexaferrites sintered at low-temperature, such as low magnetic loss tangent, low dielectric constant and loss tangent, SiO2 was introduced. The effects of SiO2 additive on the phase composition, microstructures and high-frequency electromagnetic properties of the ceramics prepared by a solid-state reaction method were investigated. The results from XRD show that in the doped samples the major phase, Z-type phase, coexists with a small amount of silicate phase. The grain growth of ceramics is suppressed by SiO2 concentrated on grain boundaries and formed block stacking structure. As SiO2 content increases, the static permeability and the dielectric constant continuously decrease. The samples with SiO2 have lower magnetic loss tangent than that of the undoped sample. Meanwhile, all the samples with SiO2 additive exhibit a low dielectric loss in the range of 400 MHz to 1 GHz. These materials are the excellent candidates to produce chip inductors for high-frequency use.