Magnetic and dielectric properties of NiCuZn ferrite with optimized Cu content and sintered by a two-step process

Highlights: • NiCuZn ferrite was fabricated through a simple approach. • The sintering temperature of the NiCuZn ferrite is reduced with the two-step sintering method. • The NiCuZn ferrite exhibits high permeability for the synergistic effect. -- Abstract: Nickel-copper-zinc (NiCuZn) ferrites with high permeability and low magnetic loss have high application potential in high-frequency electronics. In this work, NiCuZn ferrite samples with different Cu contents were prepared by a two-step sintering method. First, the optimal temperatures of the two-step sintering method (1025/925 °C) were confirmed, thereafter the influence of the Cu content on the crystal structure, microstructure, magnetic and dielectric properties of NiCuZn ferrite were studied in detail. Structural characterization showed that an increase in Cu content promoted grain growth and resulted in NiCuZn ferrites with a denser microstructure and decreased porosity. However, a second phase of CuO formed once the content of Cu (x value) reached 0.16. The magnetic hysteresis loops revealed that the saturation magnetization increased as x increased and the highest value of 57.3 emu/g was obtained at x = 0.14. The dielectric property measurement showed that increasing the Cu content could improve the dielectric constant and reduce the dielectric loss. The permeability measurements showed an increase in permeability with Cu content from x = 0.10 to x = 0.14 and a decrease when x = 0.16. Consequently, a NiCuZn ferrite with an appropriate microstructure and with high permeability (μ'=855), low magnetic loss (tanδ_μ = 0.02), and high saturation magnetization (57.3 emu/g) could be obtained at a Cu content of x = 0.14 and sintering temperatures of 1025/925 °C in the two-step sintering method. This NiCuZn ferrite provides new guidance for developing RF frequency multilayer inductors.