Microwave sintering of high-permeability MgCuZn ferrite at low sintering temperatures suitable for microinductor applications

Abstract

Mg0.40Cu0.10Zn0.50Fe1.95O4-δ ferrite samples were prepared by the microwave sintering (MS) and conventional sintering (CS) techniques. The samples were then characterized by the x-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive x-ray spectrometry (EDS) techniques. All the compositions showed single-phase cubic spinel structure. The lattice constants of MS samples were found to have lower magnitude than those of CS samples. The densities of microwave-sintered samples were higher than those of conventionally sintered samples. The temperature dependence of initial permeability was studied in the temperature range 30–150 °C at 10° temperature intervals. It was noted that the initial permeability of MgCuZn ferrites prepared by the MS method was higher than that of MgCuZn ferrites prepared by the CS method. The initial permeability (μi) magnitude of about 2300 at 10 kHz is achieved for microwave-sintered (Mg0.40Cu0.10Zn0.50Fe1.95O4−δ) ferrite, at only 950 °C sintering temperature. In addition, the sintering time of ferrites was reduced from 5 h to 20 min by using the MS technique. The low-temperature-sintered MgCuZn ferrites prepared possess good electromagnetic properties, as well as good microstructure, thus making them suitable materials for multilayer chip inductors (MLCIs) having high performance and low cost.