Tuning the interfacial reaction between CaO–SrO–Al2O3–B2O3–SiO2 sealing glass–ceramics and Cr-containing interconnect: Crystalline structure vs. glass structure

Abstract In this paper, Al 2 O 3 was added to CaO–SrO–B 2 O 3 –SiO 2 sealing system to tailor the structure of sealing glass–ceramics and glass–ceramics/metal interfacial reaction. The addition of alumina in glasses contributes to increasing fraction of bridging oxygen in silica tetrahedral as well as the change in boron environment from three-fold to four-fold (BO 4  → BO 3 ). The devitrification tendency of glasses also decreases with increasing Al 2 O 3 content. The condensed glass structure and increasing residual glass content play opposite roles on the interfacial reaction, consequently resulting in a maximum fraction of Cr 6+ in reaction couples between Cr 2 O 3 and glass containing 6 mole% Al 2 O 3 at 700 °C. In addition, the good bonding can be observed at the interface between Cr-containing interconnect (Crofer 22APU) and glass containing 4 mole% Al 2 O 3 , held at 700 °C for 100 h. The reported results support the suitability of the prepared glass–ceramics as sealing materials for SOFC applications.