Calcium–Borosilicate Glass-Ceramics as a Sealant for Solid Oxide Fuel Cells

The applicability of calcium–borosilicate glass-ceramics with high boron oxide content as a sealant for solid oxide fuel cells is studied. Chemical composition of the studied materials is: 33 mol % CaO, 21 mol % B₂O₃, and 46 mol % SiO₂. The material is studied as an alternative to the existing calcium– and barium–aluminosilicate-based sealants because of the latters’ limited adhesion to steel interconnects in fuel cells. The studied sealant is shown to have a softening point of about 920–930°C, which allows using it for sealing of fuel cells at 925°C. Use of relatively low sealing temperature allows avoiding overheating of the cell during the sealing and avoiding the accompanying degradation of the battery operational characteristics. The studied sealant demonstrated excellent adhesion to the surface of interconnect materials (the Crofer 22 APU steel). Furthermore, the studied sealant is found to be thermomechanically compatible with the Crofer 22 APU steel and ZrO₂-based electrolytes.