The Research Of Low Temperature Co-Fired Li-Zn Ferrite

LiZn ferrite is a kind of good gyromagnetic materials with high remanence square ratio?Br Bs?and low coercivity?Hc?.It has been widely used in microwave devices,such as the ferrite phase shifter.However,the LiZn ferrite needs to be sintered under high temperatures by traditional methods?above 1100??.The temperature is greatly higher than that of the melting point of silver.For manufacturing low temperature co-fired ceramics?LTCC?devices,it is crucial to decrease the sintering temperature to al ow the co-firing of LiZn ferrite with low-melting-point silver electrodes.Usual y,people would use low melting point oxides or glasses to reduce the sintered temperature of the ferrite.In this thesis,we have studied the effects of Bi₂O₃-Al₂O₃,Bi₂O₃-MgO,and MABS?MgO-Al₂O₃-B₂O₃-SiO₂?glass on LiZn ferrites.And we designed and optimized a LiZn ferrite phase shifter by using Ansoft HFSS.Firstly,we studied the effects of compound additives?Bi₂O₃-Al₂O₃,Bi₂O₃-MgO?on Li0.35Zn0.30Mn0.05Ti0.1Fe2.05O4 ferrites.The results indicated:?1?Doping moderate Bi2O3-Al₂O₃ can promote the crystal growth,increase the density and the magnetic saturation induction?Bs?,reduce the cocercivity?Hc?and the ferromagnetic resonance line width??35?H?.And the Bi₂O₃-Al₂O₃ content shouldn't be more than 1.0 wt.%.?2?When the Bi₂O₃-MgO content is 1.2 wt.%,the sintered temperature could decrease to 920?,LiZn ferrites has the high density and good gyromagnetic properties.Secondly,we studied the effects of MABS glass on Li0.35Zn0.30Mn0.05Ti0.1Fe2.05O4ferrites.The results indicated:?1?Doping moderate MABS glass can promote the solid-phase reaction,increase the crystal size and density of ferrites.?2?When the MABS glass content is 0.5 wt.%,the coercivity?Hc?is 207.03 A/m,the saturation magnetic induction?Bs?is 304.47 mT,the ferromagnetic resonance line width??35?H?is 262 Oe,the saturation magnetization?4?Ms?is 4205 Gs,and the density is 4.505 g/m³.Lastly,we designed and optimized a LiZn ferrite phase shifter.The results indicated:?1?When the length of LiZn ferrite is 23.5mm,performances of the phase shifter are as follows:in the frequency bandwidth of 33-35GHz,the phase shift is 360°,the VSWR is less than 1.28,and the insertion loss is less than 1.68dB.?2?When the length of LiZn ferrite is 27mm,performances of the phase shifter are as follows:in the frequency bandwidth of 33-35GHz,the phase shift is 430°,the VSWR is less than 1.18,and the insertion loss is less than 2.27dB.