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

Phase shifters have been studied as a critical unit in phased array radar for a long time.In recent years,for the manufacture of microwave devices,more and more attentions were paid to miniaturization and integration.Low-temperature co-fired technology(LTCC)has been proposed for meeting these requirements.However,LTCC technology needs relatively low temperature because sintering temperature is expected to be below the melting point of the co-fired silver electrode(?961 ?).LiZn ferrite materials have been widely studied due to their widely adjustable saturation magnetic induction,low coercivity and ferromagnetic resonance line width.Meanwhile,because of its gyromagnetic properties,it can be used in phase shifter,which is a basic unit of phased array.Generally speaking,the sintering temperature of LiZn ferrite materials is high(?1160?C).On the one hand,such high temperature will cause lithium volatilization.On the other hand,it will be difficult to meet the current process requirements for device miniaturization.This paper mainly studies the low temperature sintering characteristics of LiZn ferrite materials.Three additives,including Bi2O3-CuO,Bi2O3-Al2O3,Bi2O3-B2O3,were added into the pre-sintered LiZn materials.With proper number of additives,LiZn ferrite samples were obtained at low temperature(<950?).The microstructures of obtained samples confirmed that the grains obviously grow under the proper number of dopants.At the sintering temperature of 920?,with addition amount of 0.6wt%Bi2O3-0.9wt%CuO,Bs=238.02 mT,Hc=420.71 A/m,?H-391 Oe.At the sintering temperature of 920?,0.6wt%Bi2O3-Al2O3(Bi2O3:Al2O3=2:1)as dopant,Bs=340.37 mT,Hc=116.51 A/m,?H=187 Oe.At the temperature of 920?,with 0.5wt%Bi2O3-0.lwt%B2O3 doped,Bs=270.43 mT,Hc=227.52 A/m,?H=280 Oe.Three phase shifters based on LiZn ferrite material were designed and simulated by computer.Finally,for the waveguide phase shifter,the value of phase shift is 380°,|S21|<2 dB,|s11|>15 dB,VSWR<1.5.For stripline phase shifter,the phase shift is 348°,|S21|<2 dB,|S11|>10 dB,VSWR<2.For microstrip line phase shifter,the phase shift is 340°,|621|<1.63 dB,|S11|>12.5 dB,VSWR<1.54.