Microwave sintering of high-permeability (Ni0.20Zn0.60Cu0.20)Fe1.98O4 ferrite at low sintering temperatures

The (Ni_0.20Zn_0.60Cu_0.20)Fe_1.98O₄ ferrite was sintered using microwave sintering and conventional sintering technique, respectively. It was found that microwave sintering technique can effectively promote the forward diffusion of ions and thus accelerate the sintering process, resulting in the grain growth and the densification of matrix. At the low frequency of 100 kHz, the magnetizing contribution of domain wall motion is predominant, and compact and coarse matrixes are favorable for domain wall motion, giving rise to improvement of relative initial permeability and loss of ferrites. Using microwave sintering technique, for the (Ni_0.20Zn_0.60Cu_0.20)Fe_1.98O₄ ferrite, the relative initial permeability μ_i of about 2000 and the relative loss factor tanδ/μ_i of about 8.7×10⁻⁶ at 100 kHz were achieved at only 980 °C sintering temperature. In addition, the sintering time of ferrites was reduced from 5 to 0.5 h by using microwave sintering technique.