Phase transformation of yttria-stabilized zirconia (3 mol% Y2O3) in fuel cell caused by manganese diffusion

Abstract

The diffusion coefficient of Mn in yttria-stabilized zirconia (YSZ, 3 mol%Y2O3) and the structural change in YSZ have been investigated. The diffusion coefficients of Mn were determined to be 7 × 10-14m2/s at 1573 K and 2 × 10-13 m2/s at 1673 K by analyzing the concentration profiles of Mn in YSZ/Mn3O4 diffusion couples. The solubilities of MnOx were 7.4 mol% and 7.6 mol% at 1573 and 1673 K, respectively. Remarkable grain growth was observed on the YSZ side near the interface. The dissolution of MnOx almost up to the solubility limit of 7.6 mol% resulted in grain growth and the phase transformation from the tetragonal phase to the fluorite-type cubic phase. These results were discussed by comparing with the previous studies on the ZrO2-Y2O3-MnOx ternary system and on the ZrO2-MnO binary system.