Microstructure and Strength of Al2O3/Al2O3 Joints Bonded with ZnO-Al2O3-B2O3-SiO2 Glass-Ceramic

ZnO-Al2O3-B2O3-SiO2 (ZABS) glass powder was used as interlayer to join alumina ceramics. The effect of joining temperature on the microstructure and strength of joints was investigated. The results showed that the ZABS glass can react with alumina substrate to form a layer of ZnAl2O4 at Al2O3/glass interface. Bending test exhibited that low joining temperature (1150 degrees C) led to low joint strength due to the formation of pores in the interlayer, originated by high viscosity of the glass. High joining temperature (1250 degrees C) also resulted in low joint strength, because of large CTE (coefficient of thermal expansion) mismatch between amorphous interlayer and alumina substrate. Therefore, only when the joining temperature was appropriate (1200 degrees C), defect-free interface and high joint strength can be obtained. The optimum joint strength reached 285 MPa, which was the same as the base material strength.