Phase formation process, microstructure and magnetic properties of Y-type hexagonal ferrite prepared by citrate sol–gel auto-combustion method

Y-type hexagonal ferrites were prepared by citrate sol–gel auto-combustion method (CSAM). The phase formation process, microstructure and magnetic properties were investigated and compared with those of the samples made by conventional solid-state reaction method (SSRM). The selected material system has stoichiometric composition of Ba2Zn1.2−xCoxCu0.8Fe12O22, where x was varied from 0 to 1.2. Phase formation was characterized by powder X-ray diffraction (XRD). The microstructure was observed via scanning electron microscopy (SEM). Frequency spectra of complex permeability were measured via an impedance analyzer. Results reveal auto-combusted powders are about 22 nm and very active. Phase formation temperature and sintering temperature are both 900 °C, much lower than those in SSRM. The sintered samples have fine-grained microstructure. The samples exhibit better magnetic properties in hyper-frequency than those made by SSRM. As zinc content increases, the permeability μ′ is enhanced and the cut-off frequency drops. The magnetic properties are also correlated with the sintering temperature and microstructure. Permeability μ′ increases with the rise of sintering temperature.