Silver particle interlayer with high dislocation density for improving the joining of BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ electrolyte and AISI 441 interconnect

One of the critical challenges for the protonic ceramic fuel cell stack is sealing electrolytes and interconnects. However, the traditional Ag[sbnd]CuO sealant will aggravate the oxidation along the interconnect surface and result in brittle compound layers at the BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ (BZCYYb) electrolyte interface. The present work demonstrates that a silver particle interlayer with high dislocation density can be adopted to join BZCYYb electrolyte to the interconnect (AISI 441 stainless) in air instead of traditional Ag[sbnd]CuO sealant. Elevating temperatures result in a sufficient bonding at the Ag/BZCYYb interface, and a defect-free joint is obtained at 950 °C. Atomic bonding at Ag/BZCYYb interface is confirmed by TEM. Also, a dense and thin oxide layer (2–3 μm) is formed along the AISI 441 interface. Ag particles in the interlayer provide the main driving force for the sintering joining. The massive dislocations promote the recovery and recrystallization of the Ag interlayer, as well as the interdiffusion of BZCYYb/Ag. After aging in the wet oxidizing atmosphere at 600 °C for 300 h, joints remain intact and dense, indicating superior oxidation resistance and aging performance. Besides, the joint shear strength (25.3 MPa) is 59 % higher than that of the joint brazed by traditional Ag[sbnd]CuO.