Enhancement of joining interface of barium and barium–zinc borosilicate glass–ceramic SOFCs sealant by CaO and SrO addition: crystallization behaviour and microstructural aspects

Sealant properties of CaO- and SrO-containing BaO–B₂O₃–SiO₂ and BaO–ZnO–B₂O₃–SiO₂ glasses were first reported in this work. CaO and SrO were used as glass modifiers to improve thermal properties and optimize CTE value and possess a good joining interface between SOFC components. Addition of CaO and SrO enhanced the glass transition and softening temperature due to the higher ionic field strength of Ca and Sr ions promoting the boroxol ring formation and a denser glass network. IR spectra confirmed a less significant effect of CaO and SrO in the glass structures. Addition of doubled CaO and SrO retained the compatibility of CTE to that of SDC electrolyte and Crofer22APU interconnect. Crystalline phases with compatible CTE were formed in the CaO- and SrO-containing glass ceramics. This provided good adhesion without defects at the interface, which is close to the electrolyte and interconnect after prolonged operation at 800°C for 50 h.