Novel two‐step method for joining alumina ceramic by using Al ₂ O ₃ powder followed by glass infiltration

Abstract In this work, a novel two‐step joining method was developed to join alumina ceramics for high‐temperature applications. First, alumina ceramics were bonded using Al 2 O 3 powder at 1550°C. Subsequently, the Dy 2 O 3 –Al 2 O 3 –SiO 2 glass was infiltrated into the interlayer at 1450°C to obtain the alumina/alumina joints with dense composite interlayer composed by Al 2 O 3 , Dy 2 Si 2 O 7 , and few glass phase. The content of Al 2 O 3 in the composite interlayer reached 52.7%. As a result, the coefficient of thermal expansion mismatch between the interlayer and the alumina ceramic was reduced to only 2%. The flexural strength of the joints at room temperature was equivalent to that of the alumina ceramic. Furthermore, the flexural strength of the joints at 1000°C reached about 90% of that of alumina ceramics under the same conditions. After the thermal cycles from room temperature to 1000°C for 50 times, there was no significant change in the flexural strength of the joints.