Joining dense Si₃N₄ to porous Si₃N₄ by using an anorthite based glass-ceramic

This study focuses on the design, characterization and testing of a novel anorthite based glass-ceramic solder for joining dense Si₃N₄ and porous Si₃N₄ ceramic. It was found that the glass solder possesses a favorable wetting ability on two ceramic surfaces. Additionally, the influence of crystallization treatment on the microstructure and shear strength of joints was investigated. The results showed that CaAl₂Si₂O₈ was the main product in the seam. After crystallization treatment, the crystallinitiy of the seam and shear strength of joints were improved obviously. The shear strength of joints after crystallization was 52 MPa at room temperature, and it increased to 59 MPa at 850°C. Finally, the joining mechanism of the dense Si₃N₄/glass-ceramic/porous Si₃N₄ bonded joints was proposed. Intergranular diffusion of elements was identified as the main mechanism of bonding in the interface of dense Si₃N₄/glass-ceramic. In the porous Si₃N₄ side, the bonding was achieved by infiltration that was controlled by capillarity and resistance of the viscous forces.