Fracture toughness of glass sealants for solid oxide fuel cell application

• Indentation-crack length and -opening displacement were used to evaluate toughness.
• Two rare-earth glasses containing La2O3 and Y2O3 were compared.
• Presence of La+3 was known as responsible of progressive devitrification.
• Higher crystallinity led to higher hardness, stiffness and fracture toughness.

Glass and glass-ceramics are versatile materials and have been widely used for sealing in the ongoing development of intermediate temperature solid oxide fuel cell (SOFC) technology where its integrity is crucial for reliable operation of the stack. The fracture toughness is a key parameter required for the prediction of the mechanical performance of a seal glass. A comparative indentation study on two RE-glasses (RE=La and Y) was performed to evaluate their fracture toughness. Indentation toughness was calculated both through measurements of the indentation crack lengths and of crack-opening displacements in the near regions of a crack tip. Both approaches exhibited good agreement. La-containing glass showed higher stiffness, hardness and fracture toughness, which has been related to the in-situ toughening mechanism caused by devitrification and formation of crystalline phases.