TiO₂ containing glass sealant for protonic ceramic fuel cell applications: Microstructure, strength and stability studied in sealing of BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ electrolyte to Crofer 22H interconnect

To address the challenges of protonic ceramic fuel cell (PCFC) stack sealing, a TiO₂-containing alkaline silicate glass, named STKN, was utilized to seal the BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ (BZCYYb) electrolyte and Crofer 22 H stainless steel, achieving a sufficient bonding. The formation of the BaTiSi₂O₇ reaction layer at the BZCYYb interface is the key to realizing effective joining. Elevating the joining temperature results in a thicker BaTiSi₂O₇ reaction layer and a concomitant loss of the sealant. The optimal sealing parameter is determined to be 775 °C for 30 min, yielding a maximum shear strength of 20 MPa. After aging in both oxidizing and reducing atmospheres at 600 °C for 300 h, the microstructure of the joint remained stable, suggesting excellent potential for service stability of the joint.