Glass ceramic sealants belonging to BAS (BaO-Al2O3-SiO2) ternary system modified with B2O3 addition: A different approach to access the SOFC seal issue

Four compositions in the BaO-Al2O3-SiO2 system modified with B2O3 were investigated with regard to their use as glassy seals in anode supported SOFC or iT-SOFC. The glassy system studied contains varying percentages of SiO2, Al2O3, B2O3, and high content of BaO as modifier (67-74%-wt). Their glass transition (Tg) and maximum densification point lies between 630 and 680 °C, and 734 °C to 828 °C, respectively. The viscosities of the four glasses are situated between 107 to 109.5 Pa.s, in the sealing range (730-830 °C). Heat treatment at 850 °C, revealed crystalline phases identified as BaAl2Si2O8 (hexacelsian) and BaSiO3. The thermal expansion coefficient (TEC) of the obtained glasses (8.8-10.5 ppm/K) was comparable to zirconia (YSZ) electrolyte, and shows chemical compatibility and high characteristic bond strength (up to 33 ± 7 MPa). The compositions with higher BaO content in the system studied seem to be good candidates for iT-SOFC sealant application.