Glass ceramic sealants belonging to BAS (BaO-Alsub(2)Osub(3)-SiOsub(2) ternary system modified with Bsub(2)Osub(3) addition

Abstract

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 contentin the system studied seem to be good candidates for iT-SOFC sealant application.