Microstructure, electrical, and magnetic properties of NiZnCo ferrite co-doped with Bi2O3 and Nb2O5

This study investigates the effects of co-doping Bi 2 O 3 and Nb 2 O 5 on the microstructure, electrical, and magnetic properties of NiZnCo ferrites. The NiZnCo ferrites with fixed 0.3 wt.% Bi 2 O 3 doping and different Nb 2 O 5 doping contents (0–0.8 wt.%) were synthesized by state-phase reaction method. The study shows that all Ni 0.55 Zn 0.35 Co 0.1 Fe 2 O 4 samples co-doped with Bi 2 O 3 and Nb 2 O 5 exhibit a single-phase spinel structure. With increasing Nb 2 O 5 concentration, the average grain size of the ferrites increases continuously, while the porosity decreases. Furthermore, the real part of the dielectric constant rises to 2.42×10 5 , and the DC resistivity decreases to 3.08×10 5 Ω·m. The saturation magnetization varies from 40.78 to 53.29 emu/g, and the coercivity ranges from 18.00 to 19.14 Oe. Notably, among samples with different Nb 2 O 5 doping levels, the ferrite co-doped with 0.2 wt.% Nb 2 O 5 exhibits the highest initial permeability of 111.24, which is approximately four times higher than that of pure NiZnCo ferrite. These results indicate that Bi 2 O 3 –Nb 2 O 5 co-doping not only effectively regulates grain growth and porosity but also achieves a synergistic optimization of dielectric and magnetic properties. The introduction of an appropriate amount of Nb 2 O 5 leads to high initial permeability and moderate DC resistivity, helping to reduce mismatches between magnetic and dielectric losses. The combination of high dielectric constant and favorable magnetic response enhances the impedance matching and energy dissipation capabilities of the material for electromagnetic waves. Therefore, this co-doped ferrite offers a promising material candidate for the design of electromagnetic absorbers and soft magnetic components.