Effect of bismuth oxide on crystallization and sealing behavior of barium borosilicate glass sealant for SOFCs

Barium borosilicate glasses (BaO-SiO2-B2O3) with the addition of 5-25 wt% bismuth oxide as additive (equivalent to 1.23-5.88 mol% of Bi2O3 in glasses) were prepared for using as a sealant for planar solid oxide fuel cells. The effect of Bi2O3 addition on thermal properties, structure, crystallization and joining interface of the BaO-SiO2-B2O3 glasses was investigated. IR spectra showed a significant effect of Bi2O3 addition in the BaO-SiO2-B2O3 glass structure, causing a progressive conversion of [BO3] to [BO4] unit in the glasses. The Bi2O3 addition made the BaO-SiO2-B2O3 glass network less rigid resulting in a decrease of a glass transition temperature and a softening point but still maintains the thermal expansion match between the Bi2O3-containing glasses and samaria-doped ceria solid electrolyte as well as an iron-chromium metallic interconnect. 5-wt% Bi2O3 obviously decelerated the crystallization of the Bi2O3-containing glasses. Good adhesion of the 5-wt% Bi2O3-coritaining glass sealant with samaria-doped ceria electrolyte and iron-chromium metallic interconnect without any gaps was achieved at prolong test for 30 h at 800 degrees C.