| The development of mobile communication technology has promoted the advent of the 5G era,which has made extensive research on microwave dielectric ceramics that could be applied to microwave communication systems.Ba(Mg1/3Ta2/3)O3?BMT?is widely used as a good representative of low dielectric microwave ceramics in filters,resonators,and the like.However,its higher sintering temperature hinders its application in many fields.In recent years,LTCC materials attract the attention of many experts and scholars with excellent high frequency and high Q microwave characteristics,remarkable high integration and low cost.In this paper,Ba(Mg1/3Ta2/3)O3?BMT?ceramics is the main research object.The Ba(Mg1/3Ta2/3)O3?BMT?ceramics which could be applied to the LTCC technology field was successfully prepared by two-phase compounding and B?-doping and low-melting glass doping of the composite base.The main research contents include:1.The sintering characteristics and dielectric properties of ceramics were investigated when Ba(Zn1/3Ta2/3)O3?BZT?and Ba(Mg1/3Ta2/3)O3?BMT?were combined.It has been found that an appropriate amount of Zn can promote ceramic sintering,lower sintering temperature and improve dielectric properties.Excessive Zn content causes the system to produce an additional phase during the sintering process due to the volatilization of Zn,degrading the order and dielectric properties.When the two-phase composite ratio is 0.8BMT-0.2BZT,the best microwave dielectric properties can be obtained by sintering at 1600°C for 6h:?r=25.12,Qf=92322GHz,?f=7.63ppm/oC.2.The phase composition,micromorphology,bulk density and microwave dielectric properties of ceramics were investigated when Ba(Zn1/3Nb2/3)O3?BZN?and Ba(Mg1/3Ta2/3)O3?BMT?were combined.The results show that the B?and B??positions have been substituted to form new phases Ba(Mg1/3Nb2/3)O3?BMN?and Ba(Zn1/3Ta2/3)O3?BZT?.As the proportion of BMT increases,the order degree of the system increases,the optimum sintering temperature increases,and the dielectric properties increase accordingly.3.The variation trend of sintering temperature and dielectric properties of0.8BMT-0.2BZT ceramics with MnCO3 doping was studied.The results show that a proper amount of MnCO3 can reduce the compact sintering temperature of ceramic system but excessive MnCO3 will destroy the dense structure of the ceramic and cause the Qf value to deteriorate.4.The phase composition,microscopic morphology,sintering temperature and dielectric properties of B?-site substitution of Y3+on 0.8BMT-0.2BZT ceramics were studied.The results show that the proper amount of Y3+substitution can promote the sintering of ceramics,and the sintering temperature drops a lot.The excess Y3+will affect the ceramic compactness.The best dielectric properties were obtained when the amount of substitution of Y3+was 0.02mol:?r=25.22,Qf=52376GHz,?f=4.88 ppm/oC.5.In the prepared Ba{[(Mg0.8Zn0.2)0.98Y0.02]1/3Ta2/3}O3?BMZYT?ceramics with excellent performance,the sintering temperature drops below 950°C by adding La2O3-B2O3-ZnO?LBZ?glass.The results show that the LBZ glass will form a liquid phase during the sintering process to promote the densification of the ceramic,but the excess LBZ glass will cause the crystal grains to grow abnormally and destroy the dense structure.The best dielectric properties were obtained when the LBZ doping amount was 3wt.%and held at 900°C for 6h:?r=22.59,Qf=11051GHz,?f=5.69ppm/oC.6.By adding Li2O3-B2O3-SiO2?LBS?glass,the sintering temperature of BMZYT is lowered to about 900°C and more excellent microwave dielectric properties are obtained.Similarly,the right amount of LBS glass will also form a liquid phase during the sintering process,which will promote the sintering of the ceramic and reduce the sintering temperature.Excess LBS glass will form too much liquid phase,causing the grain to grow,forming more pores,destroying its dense structure and deteriorating its dielectric properties.Optimum dielectric properties when LBS doping amount is0.5wt.%:?r=24.71,Qf=18870GHz,?f=4.27ppm/oC. |
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