Fracture and creep of glass–ceramic solid oxide fuel cell sealant materials

• Partially crystallized sealants showed thickness dependent fracture stress.
• Measured fracture stress is affected by residual stress.
• Creep rate dependent on crystallization stage.
• Partially crystallized sealant shows enhanced creep and reduced strength.

The reliable operation of solid oxide fuel cell stacks depends strongly on the structural integrity of the sealing materials. In this respect, failure and deformation are aspects which need to be assessed in particular for glass–ceramic sealant materials. Bending tests and compressive tests were carried at room temperature and typical stack operation temperature for sintered bars and stack similar head-to-head joined glass–ceramic sealants specimens with different degree of crystallization and annealed temperature. The sealant material was screen printed onto the steel. Fracture stresses and creep data are reported. The results reveal a thickness dependent fracture stress and a decrease of the fracture stress for the partially crystallized sealant at operation relevant temperatures that can be associated with the residual stress state and viscous deformation of the material, respectively. A stable thickness independent fracture stress was obtained for the fully crystallized sealant. Fractographic based analysis gave insight into the failure origin.