Y₂W₃O₁₂@SiO₂ composite particles for regulating thermal expansion and interfacial reactions in BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ/AISI 441 joints

Y₂W₃O₁₂ particles with negative thermal expansion (NTE) can offset the high thermal expansion of Ag-based sealants, thus relieving the residual stress of electrolyte/interconnect joints in protonic ceramic fuel cell (PCFC) stacks. Nevertheless, violent interfacial reactions between Y₂W₃O₁₂ particles and BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ electrolyte have severely restricted the application of these NTE particles. Herein, novel Y₂W₃O₁₂@SiO₂ composite particles with a core-shell structure are successfully designed to address this conundrum. The thermal expansion coefficient of Ag-based sealant is lowered from 19.7 to 14.6 ppm/K by adding 20 wt% Y₂W₃O₁₂@SiO₂ particles. During joining, the SiO₂ shell significantly reduces the reaction consumption of Y₂W₃O₁₂, fully exploiting its NTE properties. Meanwhile, a tiny portion of SiO₂ participates in and regulates interfacial reactions, generating mechanically matched reaction layers. Finite element simulation demonstrates that introducing Y₂W₃O₁₂@SiO₂ particles significantly releases the compressive X-stress near the BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ interface, thus increasing the joint strength from ∼25.3 to ∼32.4 MPa. Obtained joints maintain long-term stability in oxidizing and reducing atmospheres at 600 °C, suggesting the applicability of Y₂W₃O₁₂@SiO₂ composite particles in fabricating PCFC stacks. Our work provides a new strategy for preparing NTE materials with controllable interfacial reactions and service capability under extreme conditions.