Preparation And Investigation Of Li₃Mg₂NbO₆ Microwave Ceramic Materials

With the advent of the 5G era,electronic devices tend to be integrated and microwave communications tend to be high-frequency.As a new type of electronic materials,microwave dielectric ceramics have put forward higher requirements for its performance in order to adapt to the rapid development of science and technology.A lower sintering temperature,an excellent quality factor（Q×f）,a dielectric constant（ε_r）which suitable for practical applications and an absolute value of frequency temperature coefficient approaching zero（τ_f）can realize high stability,low loss and miniaturization of the commercial requirements.Li₃Mg₂NbO₆ microwave dielectric ceramics with a rock salt structure have been researched and developed recently,but there have been many studies and reports on it.This fully shows that it has great application potential and research value as a microwave dielectric material.This thesis mainly focused on the formulation research of Li₃Mg₂NbO₆ microwave dielectric ceramics and the formulation research mainly included three aspects:First,LMZBS glass was added to Li₃Mg₂NbO₆ microwave dielectric ceramics to maintain better microwave dielectric properties and reduce the sintering temperature.Research on Li₃Mg₂NbO₆+x wt.%LMZBS（x=2-10）composite ceramics showed that adding LMZBS glass to Li₃Mg₂NbO₆ceramics could increase the density of the ceramic,improve the microstructure of the ceramic,reduce the sintering temperature and maintain better microwave dielectric properties.When the mass fraction of LMZBS glass was 4%and the sintering temperature was 925℃,the microwave dielectric properties of Li₃Mg₂NbO₆+4 wt.%LMZBS composite ceramic reached its peak:ε_r=16.02,Q×f=56455 GHz,τ_f=-18.81 ppm/℃.Then there was the study of mixing Li₂Ti O₃ into Li₃Mg₂NbO₆ microwave ceramics to achieve the purpose of improving the microwave dielectric properties.The research results showed that Li₂Ti O₃ and Li₃Mg₂NbO₆ compounded to form Li₃Mg₂NbO₆ phase and Mg O phase.As the content of x increases,the quality factor of Li₃Mg₂NbO₆+x wt.%Li₂Ti O₃（x=2-8）composite ceramics first increased and then decreased.When Li₃Mg₂NbO₆+6 wt.%Li₂Ti O₃ microwave dielectric ceramics were sintered at a sintering temperature of 1320℃for 4 hours,it got the maximum of the microwave dielectric properties and the detailed parameters:ε_r=16.51,Q×f=90967 GHz,τ_f=-28.27 ppm/℃.The last part was the study of partial substitution.The microwave dielectric properties could be improved by substituting the Nb⁵⁺ions of Li₃Mg₂NbO₆ microwave dielectric ceramics.The Nb⁵⁺ions replacing Li₃Mg₂NbO₆ ceramics were mainly W⁶⁺,(Mg_1/4W_3/4)⁵⁺,(Al_1/3W_2/3)⁵⁺three kinds of ions.The research results showed that the addition of W⁶⁺,(Mg_1/4W_3/4)⁵⁺and(Al_1/3W_2/3)⁵⁺have improved the microstructure and density of Li₃Mg₂NbO₆ ceramics.The addition of W⁶⁺and(Al_1/3W_2/3)⁵⁺ions did not produce the second phase,and the addition of(Mg_1/4W_3/4)⁵⁺ions produced Mg O phase.When the sintering temperature was 1175℃,the microwave dielectric properties of Li₃Mg₂Nb_0.98W_0.02O_6.01 microwave dielectric ceramics reached the peak:ε_r=16.42,Q×f=73037 GHz,τ_f=-23.63 ppm/℃;And when the sintering temperature was 1175℃,the microwave dielectric properties of Li₃Mg₂Nb_0.96(Mg_1/4W_3/4)_0.04O₆ microwave dielectric ceramics reached the peak:εr=16.36,Q×f=78382 GHz,τ_f=-20.33 ppm/℃;And when the sintering temperature was 1175℃,the microwave dielectric properties of Li₃Mg₂Nb_0.96(Al_1/3W_2/3)_0.04O₆ microwave dielectric ceramics reached the peak:ε_r=16.32,Q×f=83636 GHz,τ_f=-22.01 ppm/℃.