J056046 計算科学シミュレーションを用いた固体酸化物形燃料電池用ガドリニアドープセリア電解質の破壊メカニズムの解明

Abstract

In this paper, we discuss the fracture properties of gadolinia doped ceria (GDC) electrolytes for solid oxide fuel cell (SOFC), based on molecular dynamics (MD) simulation and density functional theory (DFT). The ceria based materials like a GDC are expected as electrolytes to lower the operating temperature, however, the short lifetime of GDC prevents their wide applications. Therefore, we executed the tensile test using the MD simulation and DFT calculation and obtained the Young's modulus and the fracture stress of the GDC. Both indicate phase transition where the oxygen coordination number of Ce^<4+> ions changes from eight to six after the yield point. Furthermore, we calculated the Young's modulus and the fracture stress as functions of oxygen concentration. This result shows that the Young's modulus decreases linearly when the oxygen concentration increases, while the fracture stress is insensitive to the changes. This tendency is in good agreement with experimental data qualitatively. We also discuss the effect of steam condition on the fracture properties of GDC, and find the crack advance of GDC is accelerated by the chemical reaction with H_2O molecules.