Preparation And Improved Microwave Dielectric Properties Of Li₂Mg₃TiO₆ Ceramics System

In recent years,Li₂Mg₃TiO₆ microwave dielectric ceramics have been became one of the research focuses in functional ceramics due to their excellent microwave dielectric properties.In this paper,Li₂Mg₃TiO₆ microwave dielectric ceramics were prepared by solid state reaction,and their structures and properties were optimized by ions doping.The relationship between structure and properties was analyzed by means of complex chemical bond theory,lattice vibration spectrum and structural parameter calculation.In this paper,the dielectric response principle of microwave dielectric ceramics has been developed,and a series of research results with theoretical and engineering application have been obtained,which provides a theoretical basis for the development and application of the new microwave dielectric ceramics.?1?Co²⁺ions were used to substitute Mg²⁺in order to improve the microwave dielectric properties of Li₂Mg₃TiO₆,and effects of Co²⁺ions on the phase composition,crystal structure,sintering characteristics,chemical bond parameters and microwave dielectric properties were systematically studied;The crystal structure changes of Li₂(Mg_1-x-x Co_x)₃TiO₆?0?x?0.4?ceramics were analyzed based on the Rietveld refinement method.The structural parameters were calculated and the relationship between these parameters and microwave dielectric properties was established;Based on the complex chemical bond theory,the chemical bond parameters were calculated,and the relations between these parameters and the microwave dielectric properties were established.The application range of the chemical bond theory of complex crystals was extended and the experimental basis for the study of dielectric response mechanism of microwave dielectric ceramics from chemical bond properties was provided.At the sintering temperature of 1600?,Li₂(Mg_1-xCo_x)₃TiO₆?x=0?ceramics possessed good microwave dielectric properties:?_r=14.31,Q·f=139,200GHz and?_f=-12.39ppm/?.?2?(Mg_1/3Ta_2/3)⁴⁺ions were used to substitute Ti⁴⁺in order to improve the microwave dielectric properties of Li₂Mg₃TiO₆,and effects of(Mg_1/3Ta_2/3)⁴⁺ions on the phase composition,crystal structure,sintering characteristics,structural parameters and microwave dielectric properties were systematically studied;The crystal structure changes of Li₂Mg₃Ti_1-x(Mg_1/3Ta_2/3)_xO₆?0?x?0.2?ceramics were analyzed based on the Rietveld refinement method.The structural parameters were calculated and the relationship between these parameters and microwave dielectric properties was established;The chemical bond parameters were calculated based on the complex chemical bond theory,and the relationship between these parameters and microwave dielectric properties was established.At the sintering temperature of 1550?,Li₂Mg₃Ti_0.95(Mg_1/3Ta_2/3)_0.05O₆ ceramics possessed excellent properties:?_r=14.70,Q·f=200,600GHz and?_f=-11.83ppm/?.Moreover,effects of LiF additions on the sintering behavior,phase compositions,micro-structure and microwave dielectric properties of Li₂Mg₃Ti_0.95(Mg_1/3Ta_2/3)_0.05O₆ ceramic were investigated systematically.3 wt.%LiF could reduce the sintering temperature of Li₂Mg₃Ti_0.95(Mg_1/3Ta_2/3)_0.05O₆ ceramic to1000? and maintain good microwave dielectric properties:?_r=15.24,Q·f=72,100GHz and?_f=-36.43ppm/?.