Microstructure, sinterability and properties of ZnO-B2O3-SiO2 glass/ Al2O3 composites for LTCC application

A new type of glass/ Al 2 O 3 ceramic composite material was prepared by the conventional solid-state method for lead-free low-softening ZnO-B 2 O 3 -SiO 2 (ZBS) glass. The effects of glass content and sintering temperature on the phase structure, sintering performance, microstructure, dielectric properties, thermal properties and mechanical properties of the composite materials were investigated by adding different mass fractions of ZnO-B 2 O 3 -SiO 2 glass into Al 2 O 3 ceramics. The results show that the doped ZnO-B 2 O 3 -SiO 2 glass effectively reduced the sintering temperature of Al 2 O 3 ceramics, and the sintering aid ZnO-B 2 O 3 -SiO 2 glass had no crystalline phase. The ZBS/ Al 2 O 3 composites sintered at 875–925 ℃ mainly contain two crystalline phases, ZnAl 2 O 4 and Zn 2 SiO 4 , and the content of the phases depended on the composition of the composites and the sintering temperature. When the content of ZnO-B 2 O 3 -SiO 2 glass was 74 wt.%, and the composites were sintered at 875 ℃ for 1 h, the volume density of the composites was 3.49 g/cm 3 , the thermal conductivity λ was 1.46W/mK, the thermal expansion coefficient CTE was 5.52/ppm ℃, the flexural strength was 155 MPa, the relative dielectric constant was 6.28, and the dielectric loss was 0.937 × 10 −3 (@12.571 GHz). The dielectric properties are the best, and it has a good application prospect in LTCC at high frequencies.