Effects of Bi2O3-Nb2O5 additives on microstructure and magnetic properties of low-temperature-fired NiCuZn ferrite ceramics

NiCuZn ferrite with superior magnetic performance is vital ceramic material in multilayer chip inductors (MLCI) applications. In this study, low-temperature-sintered Ni0.22Cu0.2Zn0.58Fe2O4 ferrite ceramic doped with 1.0 wt% Bi2O3-x wt% Nb2O5 (where x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) was synthesized via solid-state reaction method. Effects of Bi2O3-Nb2O5 additives on microstructures and magnetic properties of NiCuZn ferrite ceramics sintered at 900 °C were systematically investigated. Results indicate that an appropriate amount of Bi2O3-Nb2O5 composite additives can significantly promote grain growth and densification of NiCuZn ferrite ceramics when sintered at low temperatures. Specifically, samples doped with 1.0 wt% Bi2O3 and 0.4 wt% Nb2O5 additives exhibited excellent initial permeability (~ 410 @ 1 MHz), high cutoff frequency (~ 10 MHz), high saturation magnetization (~ 54.92 emu/g), and low coercive force (~ 20.32 Oe). These observations indicate that NiCuZn ferrite ceramics doped with appropriate amounts of Bi2O3-Nb2O5 additives are great candidate materials for MLCI applications.