| Low Temperature Co-fired Ceramics (LTCC) is a components intergration technology rose in recent years. It has become the preferred method to achieve the interation, miniaturization, and modularization of various microwave components worked in the circuits. It is widely used in military and civilian communition systems. Microwave dielectric ceramics are the key material of LTCC technology, As new electrionic materials, microwave dielectric ceramics are widely used as the core microwave components in filters and resonators fields.To satisfy the cofiring of ceramics and electrods, In these thesis, we choosed different microwave dilectric ceramics, and used BaCu(B2O5) as sintering aids to decrease the sintering temperature of these systems, the effects of BCB content on sintering temperature and microwave dielectric properties of these ceramics were also investigated.CaO-Li2O-Re2O3-TiO2 (Re=Ln, Sm, Nd) systems has an orthorhombic perovskite structure, and is widely studied due to good dielectric properties. CaO-Li2O:Sm2O3-TiO2 ceramics had good dielectric properties: Kr=110,Q·f=4500GHz, TCF=7×10-6/°C, 3GHz, when molar ratio n(CaO:Li2O:Sm2O3:TiO2) =16.0:9.0:12.0:63.0. Although this systems own high dielectric constant, low quality factor constrain Its use in high frequency. As CaO was partly substitute by BaO, with the ratio of n(CaO:BaO:Li2O:Sm2O3:TiO2)=14:4:8:12:63, CBLST ceramics exhibit a Kr=95.5, Q·f=7580GHz, TCF =-6.9×10-6/°C, 3GHz.Even though many types of dielectric ceramics have been reported, most of which could be well sintered above 1300°C. Recently, ZnO–Nb2O5–TiO2 system was found to have high dielectric properties at lower sintering temperature. Its found that 2.5ZnO–2.5Nb2O5–5TiO2 ceramics sintered at 1100°C exhibited good microwave dielectric properties of Kr=58, Q·f=16300GHz and TCF=90×10-6/°C. 1 .properties of CBLST ceramics doping with BCB BCB additive could decrease the sintering temperature of CBLST ceramics efficiently from 1325°C to 1100°C without changing the two phases of CBLST ceramics. A high relative density of 97% and good dielectric properties of Kr=87.76,tanδ=0.018, TCF=-4.27×10-6/°C(1MHz)were obtained for the 6wt% BCB-added CBLST ceramics sintered at 1100°C.2 .properties of ZNT ceramics doping with BCB BCB additive can change the degree of crystallinity of the two phase, but the ZNT ceramics always remain its main phase, BCB-dopted ZNT ceramics could efficiently decrease the sintering temperature from 1100°C to 900°C, A higher density than pure ZNT ceramics and good dielectric properties of Kr=48, Q·f=15258GHz, TCF=41×10-6/°C(5GHz) were obtained for 3wt% BCB-added ZNT ceramics sintered at 900°C. In the study of BCB-dopted ZNT ceramics cofired with Ag electrodes, we found that the interface of the ceramics and the Ag electrode was compactness and no element diffusion was observed. It was a promising LTCC microwave dielectric materials used for preparation of multilayer microwave components.
|
PDF Full Text Request