Structural Stability of the GDC Electrolyte for Low Temperature SOFCsDepending on Fuels

摘要

GDC (Gd_(0.1)Ce_(0.9)O_(1-X)) has been considered as a low-temperatureSOFC electrolyte. However, ceria cannot be efficiently used withhydrogen and wet hydrocarbon fuels because its structure change(Ce~(+4)→Ce~(+3)) causes a decline of mechanical strength under areduction atmosphere. In this work, the structural stability test ofthe GDC electrolyte for low-temperature SOFCs was investigatedunder reduction and oxidation atmospheres depending on the fuels.Each structural stability test was examined under reduction (H_2)and oxidation (dry CH_4) atmospheres at 650°C. Micro-cracks andpinholes were observed on the electrolyte surface and at thefracture after completing the test with hydrogen fuel, but in thecase of dry methane, only small amounts of defects were found atthe fracture. This study clearly confirmed from the XPS data thatmany more Ce~(+4) ions transform into Ce~(+3) ions under the reduction(H_2) atmosphere (1, 2).