Synthesis, microstructure and characterization of ultra-low permittivity CuO–ZnO–B2O3–Li2O glass/Al2O3 composites for ULTCC application

Abstract In view of lead-free low-softening CuO–ZnO–B2O3–Li2O glass, novel glass/Al2O3 ceramic composites were prepared by solid-state reaction route for ultra-low temperature co-fired ceramic (ULTCC) applications. The phase evolution and compositions, microstructure and microwave dielectric properties of the composites were studied by XRD, SEM and dielectric property measurement. Four phases including Cu2Al6B4O17, Li2CuB4O8, CuB2O4 and Al2O3 coexist in the glass/Al2O3 ceramic composites sintered in the range of 640–660 °C. However, the contents and types of the phases depend on the composition of the composites and firing temperature. The optimum properties with a permittivity er = 3.79, a quality factor Q × f = 38557 GHz (at 16.64 GHz) and a temperature coefficient of resonance frequency τf≈0 ppm/oC as well as a heat conductivity λ = 1.46W(mK)−1can be achieved for the glass/ceramic composite containing 10 wt% Al2O3 sintered at 640 °C. Moreover, the composite can be co-fired compatible with Ag and Al electrodes.The as-prepared glass/Al2O3ceramic composites are promising candidate for ULTCC application.