The Research On Performance Control Of M-phase LNT Microwave Ceramics

With the development and progress of science and technology,the modern communication industry represented by mobile communication and WLAN is also developing rapidly since the twenty-first century,which has greatly moved our demand for related electronic components.Not only that,the integration and miniaturization of microwave circuits is also one of the requirements of modern communication industry.In order to achieve this goal,the traditional metal circuit elements have been unable to satisfy the requirements,and microwave dielectric ceramics have gradually become a hot spot of research.Microwave dielectric ceramics are ceramics which are used as dielectric materials in microwave circuits and perform one or more functions.We generally divide microwave dielectric ceramics into three kinds,low dielectric constant,medium dielectric constant,and high dielectric constant.Medium and high dielectric constant microwave dielectric ceramics,which are more conducive to the miniaturization and integration of microwave circuits,are the main research objects because of their high dielectric constant.In this paper,LiNb_0.6Ti_0.5O₃?LNT?ceramics were selected as the research object,and the LiNb_0.6Ti_0.5O₃ ceramic materials were modified by the traditional solid-phase reaction method,and the two methods of two-phase composite and ion doping.We have discussed the influence of these two methods on the properties of Li Nb_0.6Ti_0.5O₃ceramics in detail,and obtained Li₂O-Nb₂O₅-TiO₂-CaO and Li₂O-Nb₂O₅-TiO₂-ZrO₂microwave dielectric ceramics.These two types of ceramics have better microwave dielectric properties compared with the original Li Nb_0.6Ti_0.5O₃ ceramics,so we have explored the properties and mechanisms of these ceramics in detail.The main phase of LiNb_0.6Ti_0.5O₃ microwave dielectric ceramics is the M-phase.It has a high dielectric constant??_r=69?,but the temperature coefficient of resonant frequency?_f is large.The microwave dielectric properties of LiNb_0.6Ti_0.5O₃ microwave dielectric ceramics sintered at 1100?for 2h were obtained:?_r=69,Q×f=5446 GHz,?_f=30.6 ppm/?,and we usually require a near zero?_f in order to obtain better temperature stability,so it needs further optimization.In this paper,the properties of Li Nb_0.6Ti_0.5O₃ ceramics are adjusted by the two phases composite method.We selected several phases with the high dielectric constant and the low temperature coefficient of resonant frequency to modify it.It is found that LiNb_0.6Ti_0.5O₃ ceramics could generate the second phase Ca₅Nb₄Ti₃O₂₁1 with doping Ca²⁺.This is a very rare phase,and we calculated that the phase has a high relative dielectric constant?_r and a low temperature coefficient of resonant frequency?_f.The Ca₅Nb₄Ti₃O₂₁1 phase has a great influence on the properties of LiNb_0.6Ti_0.5O₃ ceramics.According to the different Ca²⁺content,we have obtained a series of Li₂O-Nb₂O₅-TiO₂-CaOmicrowavedielectricceramicsLiNb_0.6Ti_?0.5-x?Ca_1.231xO₃?x=0-0.1?.When x=0.03,the sample sintered at 1100?for 2h has an excellent microwave dielectric property:?_r=76.89,Q×f=4064 GHz,?_f=0.25 ppm/?.Then we use the ion substitution method to regulate the properties of Li Nb_0.6Ti_0.5O₃ceramics.We have selected a variety of ions to replace the Nb and Ti sites.It is found that the substitution of Zr⁴⁺for Ti⁴⁺has a good effect.After doping the Zr⁴⁺,the cell parameters of the samples changed,and the volume of cell increased.A series of Li₂O-Nb₂O₅-TiO₂-ZrO₂microwavedielectricceramicsLiNb_0.6Ti_?0.5-x?Zr_x O₃?x=0.04-0.14?were obtained.When x=0.1,the sample sintered at 1100?for 2h has an excellent microwave dielectric property:?_r=63.14,Q×f=4626 GHz,?_f=1.38 ppm/?.These microwave dielectric ceramics could be applied to practice,and the related mechanisms are also explored.