Ring Used Bafe <sub> 12 </ Sub> O <sub> 19 </ Sub> Thick Film Preparation And Application Of Research

Self-biased barium ferrites micro-strip junction circulator, which possesses small size, light weight, et al characters, can be extensively applied in micro-wave communication devices. However, in order to integrate circulators with microwave components and circuits, the ferrites thin-films or thick-films must be used to replace the bulk ferrites. Barium ferrite thick films were prepared by screen printing in this thesis. The effects of sintering temperature, sintering time, sintering pressure and the magnitude of orientation magnetic field on the properties of the barium ferrite thick films were studied. Based on the barium ferrite thick films, a prototype device of micro-strip junction circulator was designed by HFSS software, and fabricated by lithography processing.The experimental results show that, a small amount of Fe₂O₃ phase presented in the thick films with increase of the sintering temperature, and the remanence ratios decrease with the increase of the sintering temperature. While, the coercivity increases at first and then decreases with the increase of the sintering temperature. The remanence ratio and coercivity are 0.58 and 5313 Oe, respectively, when the sintering temperature is 1110℃. With the increase of the sintering time, the remanence ratios of the samples increase gradually, while the coercivities decrease firstly and then increase. Pressure sintering can improve the density and the uniformity of the grain size significantly of the thick films. When the sintering pressure is 6 MPa, the optimized sintering temperature is 1110℃, and the sintering time is 10 hours, the remanence ratio and coercivity of the sample can reach to 0.66 and 5394 Oe, respectively. The remanence ratio of the thick films can be improved significantly by the orientation of the magnetic field. The grains in the thick films show obvious C-axis orientation, and the remanence ratio and coercivity increase when the orientation of the magnetic field increases. The biggest remanence ratio and coercivity at 9000 Oe orientation of the magnetic field are 0.78 and 5129 Oe, respectively. The optimized parameters are: the sintering temperature of 1110℃, the sintering time of 10 hours, the orientation of the magnetic field of 9000 Oe and the sintering pressure of 2 MPa. The optimized structural parameters of the circulator simulated by HFSS are as following, the radius of conduction band disk of the circulator of 0.97 mm, the length of the conduction strip of2.3 mm, and the width of the conduction strip of 0.6 mm. The experimental results show that the insertion loss S21 and the isolation S12 of the prepared barium ferrites thickness film prototype device circulator at 27 GHz are 8.5 dB, 12.5 dB, respectively. The maximum difference between the S12 and the S21 is 4dB, which show that the fabricated circulator exhibits obvious circulation function.