【作者】 谢辉；

【导师】 张平； 陈力颖；

【作者基本信息】 天津大学 ， 集成电路工程， 2018， 硕士

【摘要】 微波介质陶瓷是微波器件的重要组成部分,对微波通信的发展具有重要的意义。Li₂Mg₃TiO₆系陶瓷具有微波介电性能优异、原材料成本低的特点,是一种有应用前景的微波介质陶瓷。本文系统地研究了基于Li₂Mg₃TiO₆系的微波介质陶瓷的制备工艺、微观结构和介电性能。本文采用“叠层”烧结固相法制备Li₂Mg₃TiO₆系陶瓷,研究了“叠层”烧结工艺对Li₂Mg₃TiO₆系陶瓷微观结构与微波介电性能的影响。研究结果表明,该烧结工艺能够有效减少气孔和锂挥发,从而增加陶瓷的致密度。采用“叠层”的烧结工艺时,Li₂Mg₃TiO₆陶瓷具有最佳的微波介电性能:?_r¹3.2,Q×f¹56,000GHz,τ_?^-31.3ppm/℃。本文还采用了不同种类的离子对Li₂Mg₃TiO₆系陶瓷的A位或B位离子进行了取代。研究发现Ca²⁺与Zn²⁺取代Mg²⁺能够有效地改善Li₂Mg₃TiO₆系陶瓷的谐振频率温度系数。另外,Co²⁺取代Mg²⁺离子能提升Li₂Mg₃TiO₆陶瓷的Q×f值至165,000GHz,而Sn⁴⁺离子取代Ti⁴⁺离子能提升Li₂Mg₃TiO₆陶瓷的Q×f值至168,000GHz。然而,Ni²⁺或Mn²⁺的取代会降低Li₂Mg₃TiO₆陶瓷的Q×f值。本文还讨论了Li₂Mg_1-xCo_xTiO₆陶瓷的极化率、堆积密度、键价、键能对微波介电性能的影响。本文添加ZBS和LBS玻璃来降低Li₂Mg₃TiO₆陶瓷的烧结温度,研究了两种玻璃烧结助剂对陶瓷烧结特性及微波介电性能的影响,其中添加4wt%ZBS玻璃能够有效降低烧结温度至1025℃并且保持较好的微波介电性能:?_r¹3.35,Q×f¹38,800GHz,τ_?^-31.84ppm/℃。除此之外,本文通过对Li₂Mg₃TiO₆陶瓷的结构分析,进一步讨论了Li₂A_xTiO_3+x（2≤x≤4,A=Mg,Ni）系陶瓷的微观结构、烧结特性以及微波介电性能。研究表明该系陶瓷均有与MgO相似的晶胞结构,并都具有较小的谐振频率温度系数。其中,Li₂Mg_3.6TiO_6.6陶瓷在1375℃烧结有最优的微波介电性能:ε_r¹2.7,Q×f¹69,000GHz,τ_?^-32.8ppm/℃。更多还原

【Abstract】 Microwave dielectric ceramic is an important part of the microwave device and has significant effects on the development of microwave communication.Li₂Mg₃TiO₆ceramics is a promising ceramic material,which have excellent microwave dielectric properties and low cost of raw materials.In this paper,the sintering technique,microscopic structures and microwave dielectric properties of Li₂Mg₃TiO₆ dielectric properties system were investigated systematically.The main contents of the paper are as follows:In this paper,Li₂Mg₃TiO₆ ceramics was fabricated using a conventional solid-state reaction method,the effects of laminated sintering technique on the microwave dielectric properties of Li₂Mg₃TiO₆ ceramics were discussed.We found that this technique couud reduce the pores and evaporation of Li,and increase the density of ceramics.The Li₂Mg₃TiO₆ ceramics using laminated sintering technique had excellent microwave dielectric properties of?_r¹3.2,Q×f¹56,000GHz andτ_?^-31.3ppm/℃.The A-ite and B-site irons of Li₂Mg₃TiO₆ ceramics were substituted by different irons.It was found that the substitution of Ca²⁺and Zn²⁺for Mg²⁺could decrease temperature coefficient of resonant frequency.In addition,the substitution of Co²⁺for Mg²⁺could improve Q×f values of Li₂Mg₃TiO₆ ceramics to 165,000GHz,while the substitution of Sn⁴⁺for Ti⁴⁺could improve Q×f values of Li₂Mg₃TiO₆ ceramics to168,000GHz.However,the substitution of Mn²⁺and Ni⁴⁺could reduce Q×f values of Li₂Mg₃TiO₆ ceramics.The effects of polarizabilities,packing fractions,bond valence,bond energies on microwave dielectric properties in Li₂Mg_3-xCo_xTiO₆ ceramics were also discussed.The ZBS and LBS glass were added to Li₂Mg₃TiO₆ ceramics to lower the sintering temperature.Li₂Mg₃TiO₆ ceramics with 4wt%ZBS glass sintered at 1025℃displayed excellent microwave dielectric properties of?_r¹3.35,Q×f¹38,800GHz andτ_?³1.84ppm/℃.Moreover,the sintering behavior and microwave dielectric properties of Li₂A_xTiO_3+x（2≤x≤4,A=Mg,Ni）ceramics were discussed through analyzing the structure of Li₂Mg₃TiO₆ ceramics.It was suggested that this ceramics system hadthe similar structure with MgO and a small temperature coefficient of resonant frequency.Li₂Mg_3.6TiO_6.6 ceramics sintered at 1375℃had good microwave dielectric properties ofε_r¹2.7,Q×f¹69,000GHz,τ_?^-32.8ppm/℃.更多还原