Preparation And Properties Of The La₂O₃-B₂O₃ Glass-ceramic/BNT LTCC Materials With High K Value

Low temperature co-fired ceramic（LTCC）materials,which have the property of excellent high frequency,high transmission and wide pass band characteristics,has become the preferred preparation method of electronic component integration and modular,and it has been widely used in information,energy,military and the related areas.The recent researches on the LTCC materials mainly focus on the low permittivity ceramics system.However,research on the high permittivity ceramics is limited.The mainly obstacles in study high permittivity ceramics including lowering its sintering temperature under 900^oC,as well as taking dielectric properties and process adaptability into consideration.In this paper,a high permittivity（?_r>30）,low loss LTCC material was prepared,The base ceramic is BaNd₂Ti₂O₁₄（BNT）high permittivity ceramic.the La₂O₃-B₂O₃-ZnO glass-ceramic was selected as sintering aid in composite with BNT ceramic to form glass-ceramic/ceramic composite system.The sintering temperature of the base ceramic lowered under 900^oC was realized and the composite ceramic has excellent dielectric properties by designing and controlling the softening temperature and crystalline process of the glass-ceramic.The effect of ZnO on the formation of La₂O₃-B₂O₃ glass-ceramic was studied in this paper,and then the structure,phase composition,thermodynamics and dielectric properties of LBZ glass-ceramic were studied.Then LBZ/BNT ceramics with low sintering temperature and excellent dielectric properties were prepared by using LBZ glass-ceramic as sintering additives.X-Ray diffraction（XRD）,infrared spectroscopy（IR）,coefficient of thermal expansion,vector network analyzer and Thermal conductivity were used to study the effect of LBZ glass-ceramic on the sintering behavior and dielectric properties of BNT ceramics systematically.The following conclusions were obtained.The influence of ZnO on the glass formation of the La₂O₃-B₂O₃ based glass-ceramic was studied,then the structure,phase composition,thermodynamics and dielectric properties of LBZ glass-ceramic were studied.The result shows that:B₂O₃work as glass former while La₂O₃ work as network modifier and ZnO work as amphoteric oxide.Within a certain range,Increasing B₂O₃ content led to the decrease of the glass transition temperature and thermal expansion coefficient,and the increase of crystallization activation energy.When La₂O₃ contents increased,the glass transition temperatures,crystallization activation energy and thermal expansion coefficient increased.But,when ZnO contents increased,the glass transition temperature,crystallization activation energy and thermal expansion coefficient decreased.La（BO ₂）₃and LaBO₃ were precipitated after appropriate heat treatment.Precipitated crystals can greatly optimize the dielectric properties of the glass-ceramic.The dielectric loss from24.4×10^-3 down to 3.31×10^-3.BNT ceramics were prepared by solid sintering technology,The sample obtained at1350°C had a density of 5.5g/cm³.It also has a excellent dielectric properties with a permittivity,?_r=79.9,a quality factor,Q×f value=53845GHz.The LBZ/BNT composite ceramics with low sintering temperature were fabricated by using LBZ glass-ceramic as sintering additive and BNT ceramics as matrix ceramic.The sintering densification process,phase structure and dielectric proper ties of the composite ceramics were studied.The results show that there is no interfacial reaction during the sintering of LBZ glass and BNT ceramics.The crystal phase of BaNd₂Ti₄O₁₂and La（BO₂）₃ is the main phase in the composite ceramics.The densifica tion temperature range of LBZ/BNT ceramics 850℃to 900℃,with the increase of glass contents,the densification sintering temperature of the sample decreased and the density increased.The composite with 0.2La₂O₃-0.4B₂O₃-0.4ZnO and BNT ceramics could be sintered at 900℃,and the sample had the best performance:resonance frequency f=6.044GHz,dielectric constantε_r=39.61,dielectric loss tanδ=1.033×10^-3 and thermal conductivity of 0.672W/（m·K）.