Research Of Low-temperature Sintering Of LiZn Ferrites For Phase Shifter

In today’s era,international relations are becoming more and more intense,and the phased array radar system is the foundation of the game between great powers and an important indicator to measure the combat effectiveness of a country’s army.In order to adapt to the trend of miniaturization and integration,it is of great significance to develop a ferrite phase shifter with excellent performance and reduce its volume.Because of its high rectangular ratio,high saturation magnetization,high Curie temperature and low loss,LiZn ferrite has become one of the important materials for ferrite phase shifters.However,the conventional sintering temperature of LiZn ferrite materials is high（≥1160°C）,which does not meet the requirements of low temperature co-fired ceramic（LTCC）technology process.In order to combine LiZn ferrite material with LTCC process,the sintering temperature of LiZn ferrite must be lowered to below 960°C.Therefore,it is of great practical significance to develop low-temperature sintering of LiZn ferrite materials with excellent properties.In this thesis,the effects of V₂O₅-MgO and Bi₂O₃-Nb₂O₅ composite additives on the sintering temperature and gyromagnetic properties of LiZn ferrite materials were studied.By co-firing with composite additives,LiZn ferrite materials with excellent magnetic properties were obtained at a sintering temperature below 960°C.Experiments show that appropriate amounts of composite additives can promote the densification and growth of grains,improve the gyromagnetic properties,and reduce the sintering temperature of the material.At 920°C sintering temperature,when 0.9 wt.%V₂O₅-MgO（V₂O₅:MgO=2:1）was doped into the LiZn Ti Mn ferrite raw material for co-firing,the density is 4.683g/cm~3,the saturation magnetic induction（Bs）is 307.36 m T,the remanence ratio（Br/Bs）is 0.8850,the coercivity（Hc）is 204.29 A/m and the ferromagnetic resonance linewidth（ΔH）is 203.7 Oe;When 0.5 wt.%Bi₂O₃-0.10 wt.%Nb₂O₅ was doped into the LiZn Ti Mn ferrite raw material for co-firing,the density is 4.747 g/cm~3,the saturation magnetic induction（Bs）is 318.34 m T,the remanence ratio（Br/Bs）is 0.8930,the coercivity（Hc）is172.26 A/m and the ferromagnetic resonance linewidth（ΔH）is 171.2 Oe;When 0.8 wt.%Bi₂O₃-0.10 wt.%Nb₂O₅ was doped into the LiZn Ti Mn ferrite raw material for co-firing,the density is 4.715 g/cm~3,the saturation magnetic induction（Bs）is 355.02 m T,the remanence ratio（Br/Bs）is 0.8811,the coercivity（Hc）is 141.57 A/m and the ferromagnetic resonance linewidth（ΔH）is 156.6 Oe.Finally,a stripline ferrite phase shifter is designed and simulated by HFSS 15.0software.According to the design goal,the model is optimized,and finally a ferrite phase shifter meeting the target performance parameters is obtained.The phase shifter operating frequency is 33～35 GHz,the absolute value of insertion loss|S₂₁|<2.3 d B,the absolute value of return loss|S₁₁|>20 d B,the standing wave ratio VSWR is less than 1.2,and the phase shift difference reaches 400°.It has practical application prospects in phased array radar system.