Effect of Bi₂O₃-CuO Flux on the Microstructure, Soft Magnetic Properties, and Gyromagnetic Properties of NiCuZn Ferrites for LTCC Devices

In this work, the electromagnetic properties of Ni_0.22Cu_0.31Zn_0.47Fe₂O₄ (NiCuZn) ferrites doped with 0.3 wt% Bi₂O₃ + xCuO flux (x = 0.2, 0.4, 0.6, and 0.8 wt%) were studied. Doping resulted in a reduction in the sintering temperature to 900 °C. The doped ferrites were synthesized via the solid-state method. XRD patterns revealed that the prepared ferrites had a cubic spinel structure; thus, a moderate addition of flux did not change the crystal structure. The SEM images, as well as the density and grain size distribution of the samples, showed that the NiCuZn ferrites had densified, homogenized, and contained fully grown grains for x = 0.6 wt%. The sample exhibited good soft magnetic properties, with μ' reaching the maximum value of 245.4 for x = 0.6 wt% and ε', M_s, and H_c reaching the maximum values of 23.1, 28.06 emu/g, and 45.86 Oe for x = 0.8 wt%, respectively. Furthermore, the ferrites exhibited good gyromagnetic properties, with 4πM_s reaching the maximum value of 1744 Gauss for x = 0.8 wt% and ΔH reaching the minimum value of 228 Oe for x = 0.6 wt%. NiCuZn ferrites were successfully sintered at a lower temperature (900 °C) by adding Bi₂O₃-CuO flux through LTCC technology and exhibited good soft magnetic properties and gyromagnetic properties. We envisage that these ferrites could be used in multilayer devices.