Effect of Nb₂O₅ doping on improving the thermo-mechanical stability of sealing interfaces for solid oxide fuel cells

Nb₂O₅ is added to a borosilicate sealing system to improve the thermo-mechanical stability of the sealing interface between the glass and Fe-Cr metallic interconnect (Crofer 22APU) in solid oxide fuel cells (SOFCs). The thermo-mechanical stability of the glass/metal interface is evaluated experimentally as well as by using a finite element analysis (FEA) method. The sealing glass doped with 4 mol.% Nb₂O₅ shows the best thermo-mechanical stability, and the sealing couple of Crofer 22APU/glass/GDC (Gd_0.2Ce_0.8O_1.9) remains intact after 50 thermal cycles. In addition, all sealing couples show good joining after being held at 750 °C for 1000 h. Moreover, the possible mechanism on the thermo-mechanical stability of sealing interface is investigated in terms of stress-based and energy-based perspectives.