A novel non-crystallizing Na₂O-K₂O-TiO₂ silicate glass sealant for protonic ceramic fuel cell applications

Sealants play an indispensable role in the fabrication of proton ceramic fuel cell (PCFC) stacks. A TiO₂-containing silicate glass, primarily composed of Na₂O-K₂O-TiO₂-SiO₂, was developed for sealing BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ (BZCYYb) electrolyte and Crofer 22 H interconnect. The coefficient of thermal expansion of the glass sealant is 11.6 × 10⁻⁶ K⁻¹, and its glass transition temperature and softening temperature are 566 °C and 601 °C, respectively. The structure of the glass was investigated by XRD, Raman and FT-IR, indicating that it is not sensitive to high temperatures up to 800 °C. The wettability of the glass on BZCYYb and Crofer 22 H substrates was tested. An intact and defect-free BZCYYb/Crofer 22 H joint was sealed by the glass sealant at 750 °C for 30 min. The elemental distribution demonstrates that no violent reaction or diffusion of elements occurs at the interface, indicating that the Na₂O-K₂O-TiO₂-SiO₂ glass is capable of sealing PCFC stacks.