Effect of Y2O3 additive on the microstructure and high-frequency properties of Z-type hexaferrites

In order to improve the high-frequency electromagnetic properties of Z-type hexaferrites such as high cut-off frequency and low dielectric constant, Y2O3 was introduced. The influence of Y2O3 additive on the phase composition, densification, microstructural and electromagnetic properties of the ceramics with composition of Ba-3(Co0.4Zn0.6)(2)YxFe24-xO41 (x = 0-1) was investigated. The results show that as the amount of Y2O3 additive increased, the major phase changed to Z-phase; simultaneously, a small amount of garnet phase appeared. With increasing Y2O3 content, the garnet phase separated out on grain boundaries as a secondary phase restraining grain growth. When x was varied from 0 to 1, the dielectric constant decreased and the ferroelectric resonance peak shifted toward a higher frequency. Meanwhile, the initial permeability increased at first, and then decreased with further increasing x, which could be mainly attributed to the change of phase composition and sintering density. With increasing Y2O3 content, the minimum reflection point of the samples shifted toward a higher frequency. (C) 2008 Elsevier B.V. All rights reserved.