Low temperature sintering and dielectric properties of La2O3-B2O3-Al2O3 glass-ceramic/Al2O3 composites for LTCC applications

New glass-ceramic/ceramic composites based on lead-free low-softening La2O3-B2O3-Al2O3 (LBA) glass-ceramics and Al2O3 fillers were prepared. The phase compositions, microstructure, and dielectric properties of the composites were investigated. LaBO3, La(BO2)(3) and LaAl2.03(B4O10)O-0.54 including Al2O3 fillers were developed in the LBA glass-ceramics/alumina composites sintered at 875 degrees C, but the relative amounts of the phases varied greatly with different glass-ceramic compositions and were considered to be determined by the ratio of La2O3 to B2O3. The onset sintering temperatures of green composites were similar to 670 degrees C and the sintering shrinkage of the samples was mainly determined by the low-softening glass-ceramics. Optimum properties were exhibited for the composite of 25 La2O3-65 B2O3-10 Al2O3 glass-ceramic with 40wt% Al2O3 sintered at 900 degrees C with a permittivity epsilon(r)=7.91, a dielectric loss tan =2.12x10(-3) (at 8.1GHz). The low epsilon(r) and tan coupled with a low sintering temperature, suggested that the LBA glass-ceramic/Al2O3 composites were potential candidates for LTCC applications.