Study On The Properties Of High Q Dielectric Ceramics And Its Application On Devices

With the rapid advancement of technology in the communications field and the increasing demand for various types of microwave devices,the volume,weight,and reliability of microwave devices have become increasingly important.In order to meet the technical progress of these devices in the microwave communications industry,LTCC technology has emerged.Under the premise of keeping the good performance of microwave devices,simultaneously reducing the volume of the devices and improving the adaptability of microwave devices to various environments,the demand for R&D of microwave dielectric ceramics with better performance and higher stability has become increasingly More urgent.MgTiO₃ and Mg₂TiO₄ in MgO-TiO₂ system ceramics have excellent microwave performance.Therefore,this article starts with the MgO-TiO₂ system prepared and tested these three kind of ceramics under the same conditions.The density curves,compositional structures,and microstructures of the three ceramics were analyzed,and their performances were compared.Finally,one of the Mg₂TiO₄ ceramics that can perform in-depth studies was selected for further study.The reduction of the sintering temperature of Mg₂TiO₄ ceramics was achieved by replacing the Mg²⁺ions of Mg₂TiO₄ceramics with different substitutional amounts of Co²⁺ions.The experimental results show that when the substitution amount of Co²⁺ions is 0.1,the ceramics with the best performance can be obtained at a sintering temperature of 1350℃:Q×f=162265GHz,ε_r=12.769.After determining that the optimal substitution of Co²⁺ions is 0.1,the sintering temperature is lowered by doped different contents of LBBS glass into(Mg_0.95Co_0.05)₂TiO₄ ceramics,when the LBBS glass is 1.5 wt%and the sintering temperature is 1200℃(Mg_0.95Co_0.05)₂TiO₄ can get the best performance:Q×f=154123GHz,ε_r=13.215.In order to reduce the sintering temperature of(Mg_0.95Co_0.05)₂TiO₄ ceramics while making the temperature coefficient close to zero,Li₂TiO₃ is used to compound with(Mg_0.95Co_0.05)₂TiO₄,when the mass ratio of(Mg_0.95Co_0.05)₂TiO₄ to Li₂TiO₃ At 0.44:0.56,the ceramic temperature coefficient is closest to zero,and the sintering temperature at 1100℃has the following properties:ε_r=16.98,Q×f=110341GHz,τ_f=-1.3ppm/°C.After determining the optimum composite ratio,different amounts of LBBS and LBSCA glass were added to the(Mg_0.95Co_0.05)₂TiO₄-Li₂Ti O₃ ceramics for reducing the sintering temperature.When the LBBS content was 2.5wt%,the sintering temperature was 900℃.The sample can get the best performance:ε_r=19.076,Q×f=126100 GHz,τf=0.98ppm/°C.After the ceramic material was completed,the LTCC filter was designed using the sample with the best LBBS content of 2.5wt%and sintering temperature of 900℃.Excellent performance of the designed filter:center frequency f₀=2.6GHz,bandwidth300MHz,in-band insertion loss less than 2dB,reflection loss higher than 15dB,and200M out-of-band rejection greater than 20dB,which can well meet design specifications.