Preparation And Characterization Of Mid-permittivity Low Temperature Sintered Microwave Dielectric Ceramics

Microwave dielectric ceramics are used in microwave circuit as an dielectricmaterial to realize one or more functions。With the development of microwavetechnology, microwave dielectric ceramics has aroused extensive concern. LowTemperature Co-fired Ceramic （LTCC） technology is a packaging technology byfabricating multilayer chip microwave components to fulfill the requirements ofsmall-size and modularization. BTN ceramic is an potential material with moderatedielectric constant, low dissipation factor and stable crystal structure. However,BTN ceramic were not used in LTCC technology because of its high temperaturecoefficient of the resonant frequency （τ_f≈100ppm/℃） and high sinteringtemperature （>1270℃）.In this paper, we have prepared Ba3Ti4-x(Mg_1/3Nb_2/3)xNb4O21（BTMNN-x,x=0～4） ceramics and investigated the effect of the substitution of (Mg_1/3Nb_2/3)4+for Ti4+on the microwave dielectric properties of BTN ceramic. Moreover, we haverespectively used BaCu（B2O5）（BCB） and2ZnO-V₂O₅as sintering aids tosuccessfully low the sintering temperature of BTMNN-2. The experimental resultsreveal that the microwave dielectric ceramics of BTMNN-x solid solution can beprepared via the conventional solid-state reaction method. The X-ray powderdiffraction analysis revealed that the diffraction peaks were found to shift towardthe lower angles with increasing the substitution content x, which was attributed tothe expansion of unit cells. The SEM micrographs of BTMNN-x ceramics indicatedthat samples exhibited rod-like grains with the substitution, meaning that thesubstitution tends to significantly promote the grain growth. As the same time, themicrowave dielectric properties have changed with the increase of x. The dielectricconstant reduced from66to42, and the temperature coefficient of the resonantfrequency reduced from56ppm/℃to15ppm/℃, while the quality factor increasedfrom10500GHz to22500GHz with the increase of x. In addition, we added BCBto the BTMNN-2ceramic as the sintering aid to low the sintering of the ceramic.For1.5wt%BCB modified BTMNN-2samples, the overall properties of ε_r=50,Qf=10500GHz，τ_f=18ppm/℃can be possessed when sintered at950℃for2hours.Moreover, we have studied the effect of2ZnO-V₂O₅on the sintering behavior and microwave dielectric properties of BTMNN-2. With5wt%2ZnO-V₂O₅, theBTMNN-2ceramics can be well sintered at900℃and show a good microwavedielectric properties of ε_r=47, Qf=10500GHz，τ_f=16ppm/℃.