Y2W3O12@SiO2 composite particles for regulating thermal expansion and interfacial reactions in BaZr0.1Ce0.7Y0.1Yb0.1O3-δ/AISI 441 joints

Abstract

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 BaZr0.1Ce0.7Y0.1Yb0.1O3-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 BaZr0.1Ce0.7Y0.1Yb0.1O3-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.