Crystallization behavior of BaO–CaO–SiO₂–B₂O₃ glass sealant and adjusting its thermal properties for oxygen transport membrane joining application

In this work, the thermal stability of a BaO–CaO–SiO₂–B₂O₃ glass sealant, named “H”, was investigated by differential scanning calorimetry (DSC). The crystallization behavior of glass H as the sealant matrix was investigated by a combination of experimental X-ray diffraction (XRD) analysis and thermodynamic simulation with the FactSage package. A good agreement was found between the Rietveld refinement of XRD experiments and the FactSage simulation. Particular attention was also given to the influence of the Sr₂SiO₄ filler added to the glass matrix “H” on the thermal expansion and microstructures of glass-Sr₂SiO₄ composites by means of dilatometry and scanning electron microscopy (SEM). The reinforced 20 wt% Sr₂SiO₄ composite (HS2S20) showed excellent properties and, thus, its joining performance was investigated using SrTi_0.75Fe_0.25O_3-δ (STF25) and Aluchrom as promising oxygen transport membrane (OTM) and counterpart, respectively. The joining behaviors were investigated by comparing different joining temperatures. 920 °C is the best joining temperature for HS2S20 sealant.