Research Of High Gyromagnetic NiCuZn Ferrite Thick Film By Tape Casting

NiCuZn ferrite material with adjustable saturation magnetization, high Curie temperature, narrow ferromagnetic resonance linewidth is widely used in microwave devices. Millimeter wave ferrite circulator unidirectional transmission of electromagnetic waves is a key component in the millimeter wave radar and communication system. Clearly, the ferrite material affects the devices performance. In addition, in recent years, the requirements for miniaturization of electronic components have accelerated the thin / thick film ferrite materials.In this thesis, the key process parameters of tape casting and sintering had been analyzed, emphasis on the ferrite phase cast thick, microscopic morphology and gyromagnetic material. Then we obtained high gyromagnetic NiCuZn thick films. The results show that:(1) In the tape casting process of NiCuZn thick films, the slurry viscosity, casting speed, drying temperature have an important impact on the quality of green tape molding: a viscosity less than 320 MPa?s, green tape will not be stripped and keep powder form; drying temperature is higher than 40 oC, green tape appears uneven forming cracks; the number of laminated thick films has little effect on the sample phase and magnetic properties, and can be adjusted for practical application.(2) When the holding time set at 1.5 h and the sintering temperature is varied within the range of 1020~1080 oC, the saturation magnetization of the sample reaches the maximum value of 5140 Gs at 1060 oC; when the samples sinter at 1040 oC for 3.0 h, the saturated magnetization slightly increased to 5068 Gs.(3) Basing on the Relaxation theory, we analyzed the contribution of ferromagnetic resonance linewidth broadening factors under different sintering conditions and found that the poles of samples play the dominant role on broadening linewidth. Through reducing the surface roughness of the samples, the surface roughness broadening linewidth can be reduced to 10% of total linewidth.Finally, basing on the above NiCuZn thick film materials, we use the software of HFSS simulating two structures of Ka-band circulator, and the simulation results show that:(1) Single Y junction microstrip circulator has |S11| <-33 d B, |S21| <0.86 dB, VSWR <1.20, center 34 GHz frequency bandwidth of 6.0 GHz;(2) Dual Y junction microstrip circulator has |S11|<-31 dB, |S21| < 0.72 dB, VSWR <1.25, the center frequency of 34 GHz bandwidth of 8.2 GHz.