NiCuZn Ferrite Cores by Gelcasting: Processing and Properties

Abstract

We used gelcasting, a pressure-less processing technology for fabricating ceramic parts, to make NiCuZn ferrite cores, which are traditionally made by a process that requires high hydrostatic pressure. A commercial NiCuZn ferrite powder was mixed with water, dispersant, and organic monomers to form a slurry, and then cast it into a mold of toroid shape followed by sintering at 900 °C, 950 °C, and 1000 °C for two hours. The sintered core mass density was found to increase with sintering temperature. The magnetic properties of the cores, i.e., complex permeability and core-loss density, were measured. We found that the real part of the permeability increased with sintering temperature from about 44 at 900 °C to 78 at 1000 °C. The core-loss density data at 5 MHz showed that the cores sintered at 950 °C had the lowest core-loss density; approximately 50% lower than that of a commercial NiZn ferrite (4F1) core. Since gelcasting does not require pressure and is scalable and low cost, it has the potential to make magnetic cores with intricate shapes and sizes for desired coupling of magnetic fluxes to improve efficiency and power-density of power electronics converters.