Structure and sintering behavior of BaO–SrO–B2O3–SiO2 sealing glass for Al2O3 ceramic substrates

BaO–SrO–B 2 O 3 –SiO 2 sealing glass for Al 2 O 3 ceramic substrates was prepared and the effect of B 2 O 3 on its structure, sintering behavior, and properties was studied. Owing to the fluxing action of B 2 O 3 , the glass transition temperature, sintering temperature, and crystallization temperature of the sealing glass were decreased with increasing B 2 O 3 . With an increase in the B 2 O 3 /SiO 2 ratio, the average bridge oxygen number of the glass network first increased and then decreased, and the boron abnormality phenomenon was detected at a B 2 O 3 /SiO 2 ratio of 0.55, at which the polymerization degree of the glass network was maximized. Furthermore, the precipitation of BaAl 2 Si 2 O 8 crystals was promoted and the crystallinity of the sealing glass was increased, inhibiting sintering densification and weakening the material. The sealing glass with a B 2 O 3 /SiO 2 ratio of 0.55 sintered at 800 °C for 10 min showed the best properties: a thermal expansion coefficient of 7.89 × 10 −6 K −1 , flexural strength of 114.28 MPa, Vickers hardness of 622.98 HV, dielectric constant of 12.14, and a dielectric loss value of 4.11 × 10 −3 . After the sealing glass was co-sintered with the Al 2 O 3 ceramic substrate, the interface was tightly bonded. This indicates the great potential applicability of BaO–SrO–B 2 O 3 –SiO 2 sealing glass for Al 2 O 3 ceramic substrate packaging.