Electro-chemical potential analysis of zirconium based on the reaction-diffusion equations of oxygen ion and electron considering phase transformation

Phase transformations induced by the precipitation of Ni in Ni-doped 8Yttria-Stabilized Zirconia (8YSZ), which is a typical electrolyte material, have recently been known to cause electrochemical degradation of Solid Oxide Fuel Cells (SOFC). Numerical simulations are conducted to evaluate the oxygen potential distributions and then to estimate the degree of transformation during long-term operations that can be determined by the equilibrium partial pressure between Ni and NiO. The simulation results indicate that the oxidation-reduction front inside the electrolyte tends to move towards the anode side reflecting the difference in electrical conductivities with different time constants between the oxidation and reduction regions.