Joining of alumina ceramics using silicon–magnesium composite filler for high-temperature applications

This study proposes the use of a Si–Mg composite filler for low-temperature joining of alumina (Al2O3) ceramics while maintaining a high-temperature reliability. The Al2O3/Al2O3 joints were formed at 1100°C in vacuum by Si-layer formation at the joint interface; the molten Si–Mg liquid phase was transformed into a solid Si layer by Mg-evaporation-induced isothermal solidification. The joint tensile strength at room temperature was as high as 20–30 MPa on average when the initial Mg contents in the filler ranged from 43 to 53 at.-%. Such joints were examined by bending tests at 1200°C in air with a fracture stress of ∼65 MPa, which revealed their potential to be provided for use at least 100°C above the bonding temperature.