Preparation And Dielectric Properties Of Ca_0.8Sr_0.2TiO₃-Li_0.5La_0.5TiO₃ Microwave Ceramics

Microwave dielectric ceramic plays a key role in foundation material of modern electronic communication,its dielectric properties have been widely used.With the rapid development of mobile communication,microwave dielectric ceramic has become a research hotspot of functional ceramics.It is of vital importance that microwave components develop towards miniaturization,integration,high reliability and low cost.The microwave dielectric ceramics with perovskite structure own high dielectric constant,low dielectric loss and near-zero temperature coefficient.To achieve this purpose,sintering performance,phase composition and dielectric properties of xCa_0.8Sr_0.2TiO₃-?1-x?Li_0.5L_0.5TiO₃ ceramic materials in perovskite structure have been studied in this paper.Based on the result,the sintering properties,phase composition and dielectric properties of CST-LLT ceramic with different additions were also investigated to reduce sintering temperature of ceramics.The x CST-?1-x?LLT(x=0.4?_0.8)microwave dielectric ceramics were prepared by the solid state reaction method.The phase composition,microstructures and microwave dielectric properties of ceramics were investigated.The results indicate that the perovskite structures is formed.The bulk density reached the peak value 4.43g/cm3 and decreased as inceasing of sintering temperature.The dielectric constant?r varied from 154.8 to 275.2 at 1170?1260? sintering temperature with the reducing of Li_0.5La0 5TiO₃ content.The Qxf value increased first and then reduced gradually in the range of 1360GHz to 1479GHz,and the?f tvalue varied from-720.6 to 47_0.5×l0-6/?.With x=0.5,CST-LLT ceramics sintered at 1200? for 3h exhibited proper dielectric properties of ?r=230,Q×f = 1455GHz and ?f=24.5×10-6/?.To reduce the sintering temperature of CST-LLT ceramics,the _0.5CST-0.5LLT ceramic with best performed has been investigated.The _0.5CST-0.5LLT ceramics doped with Bi₂O₃ are prepared by solid phase sintering method and have orthorhombic perovskite structure.It is found that a small amount of Bi₂O₃ was added to reduce the sintering temperature by 20?.With the increase of Bi₂O₃,the dielectric constant ?r varied from 155.9 to 186.4,the Qxf value increased to the peak and then reduced in the range of 1299GHz to 1900GHz,and the?f value varied from-55 to 101×10-6/?.In general,the _0.5CST-0.5LLT ceramics doped with 2wt%Bi₂O₃ calcined at 1050? and sintered at 1180? for 3 hours showed the excellent microwave dielectric properties of ?r=219.9,Q×f= 1900GHz and ?f=18×10-6/?.The _0.5CST-0.5LLT ceramics doped with CuO-V₂O₅ are prepared by solid phase sintering method and have orthorhombic perovskite structure.The second phase began to appear when the quantity reached 4wt%.The dielectric constant of _0.5CST-0.5LLT ceramics increased to the peak and then decreased with the increase of sintering temperature.The Qxf value increased to the peak and then reduced in the range of 1268GHz to 1689GHz.Therf value decreased from positive to negative with the increase of sintering temperature.In general,the _0.5CST-0.5LLT ceramics doped with 4wt%CuO-V₂O₅ calcined at 1050? and sintered at 1170? for 3 hours exhibited the excellent microwave dielectric properties of ?r=215,Q×f=1679GHz and?f?-38×10-6/?.