Bonding sapphire in air by using Bi2O3-B2O3 glass braze

Sapphire plates were directly bonded with bismuth borate glass braze, 50Bi2O3−50B2O3 (mol%), at 700 °C for 20 min in air. The microstructure of the sapphire/sapphire joint was studied and the interfacial phases were characterized in detail. The results showed that Al4B2O9 was the main product within the joint domain, the typical microstructure of a joint was the sapphire substrate/glassy phase + Al4B2O9/the sapphire substrate.