Barium-free glass-ceramic sealants from the system CaO-MgO-B2O3-Al2O3-SiO2 for application in the SOFC

The planar solid oxide fuel cell (p-SOFC) is a promising configuration of a high-T fuel cell. Barium alumosilicate glass ceramics are suggested to use as sealants by many authors since these materials seem to meet the requirements to establish a hermetic and electrically insulating seal between the steel components of the SOFC. However, in long-term application, the formation of BaCrO4 may degrade the interfacial strength between glass-ceramics and metallic interconnect and disrupt the cell components. In this work, a series of barium-free glass-ceramics in the system of CaO-MgO-B2O3-Al2O3-SiO2 were prepared. The selected compositions were located within the constitutional range of akermanite - forsterite -anorthite. The thermal properties including glass transition temperature (T-g) and crystallization temperature (T-c) of the produced glasses were measured. The effect of boron oxide additions was studied in order to optimize the softening and flow behavior. For the experiments, a hot - stage microscope was used. Some glass compositions were mixed with high - CTE akermanite powder in order to increase their CTE after sintering. The CTE of the investigated materials after sintering at 900 degrees C, 2 h, ranged from 10.5 to 11.8 10(-6) K-1.