Galliosilicate glasses for viscous sealants in solid oxide fuel cell stacks: Part I: Compositional design

• A unique set of galliosilicate glasses are promising for SOFC viscous sealing.
• The initial flow behavior was optimized and is appropriate for the seal process.
• Heat treatments of up to 500 h were used to demonstrate viable viscous sealing.

Galliosilicate glasses were developed for sealing intermediate temperature planar solid oxide fuel cell (SOFC) stacks. Candidate sealing glasses were identified for use at operating temperatures of 750 °C and at 850 °C after assessing flow behavior, thermal expansion properties, and crystallization behavior. A series of non-alkali glasses was identified for use at 750 °C within a strontium boro-galliosilicate compositional region that exhibited glass transition temperatures (Tg) between 658 and 675 °C and coefficients of thermal expansion (CTE) between 8 and 9.4 × 10−6 K−1. Glass frits and powders flowed below 850 °C and did not crystallize dramatically after 500 h at 750 °C. Several glasses containing 5 mol% mixed alkali were identified in a strontium boro-galliosilicate compositional region for use at 850 °C. The glasses exhibited Tg between 615 and 620 °C with CTE from 7.8 to 9.7 × 10−6 K−1. Glass frits flowed well below 850 °C and retained remnant glass phase after partial crystallization at 850 °C. The galliosilicate glasses developed in this work enable viscous sealing of SOFC stacks.