Physical and thermal behaviour of Sr-La-Al-B-Si based SOFC glass sealants as function of SrO content and B2O3/SiO2 ratio in the matrix

A series of SOFC glass sealants with composition SrO (x), La₂O₃ (15), Al₂O₃ (15), B₂O₃ (40 − x), and SiO₂ (30) [x = 10, 15, 20, 25 and 30] (wt.%) [SLABS] are investigated for their structure property correlations at different compositions. Quantitative Fourier transform infrared spectroscopy shows structural rigidity with increasing SrO content, as demonstrate by an increase in the Si-O-Si/O-Si-O bending and B-O-B stretching frequencies. The role of SrO as a modifier dominates the control of the structure and behaviour of glasses compared with the effect of network formers, i.e., the B₂O₃/SiO₂ ratio. Consequent to the structural changes, increasing substitution of B₂O₃ by SrO the glasses causes increases in the density, glass transition temperature and dilatometric softening point. On the other hand, the crystallization temperatures show a decreasing trend and the coefficient of thermal expansion increases with increase in substitution.