Enhanced gyromagnetic properties of NiCuZn ferrite ceramics for LTCC applications by adjusting MnO2-Bi2O3 substitution

The demand for high performance microwave devices is increasingly promoting the development of miniaturization, integration and multifunctionalization. Here, a uniform and dense NiCuZn ferrite ceramic with high saturation magnetization and low ferromagnetic resonance linewidth was obtained at 950 °C by adjusting the MnO2-Bi2O3 composite additives. The MnO2-Bi2O3 composite additives were composed of 0.5 wt% MnO2 and x wt% Bi2O3 (x = 0.0, 0.5, 1.0, 1.5, 2.0, and 3.0). The phase structure, microstructures and magnetic properties were systematically studied by means of modern measurement techniques. SEM images reveal that appropriate MnO2-Bi2O3 additions can promote grain growth and reduce sintering temperatures, which is very advantageous for LTCC technology. In addition, the content of MnO2-Bi2O3 additives can significantly reduce ferromagnetic resonance linewidth (FMR) by promoting grain growth and densification at low temperatures. Finally, a uniform and compact NiCuZn ferrite ceramic with an improved 4πMs (~ 3812.5 Gauss), a narrow ΔH (~ 144.6 Oe), and a reduced Hc (~ 85.2 A/m) were obtained (at 950 °C) by adding the optimal volume of Bi2O3 additive. It is expected that the improved gyromagnetic performances will allow the NiCuZn ferrite ceramics to be promising candidates for X-band microwave devices.