The effect of ferroelasticity of La_1-xSr_xCo _1-yFe_yO_3-δ on the mechanical stability of solid oxide fuel cells

The stress-strain relationship of La_0.6Sr_0.4CoO _3-δ (LSC), La_0.6Sr_0.4Co _0.2Fe_0.8O_3-δ (LSCF6428) and La _0.6Sr_0.4FeO_3-δ (LSF) was evaluated by uniaxial compression tests in the temperature range between room temperature and 1173 K. A nonlinear stress-strain relationship with a residual strain was observed below the phase transition temperature, while an almost linear relationship with no residual strain was observed above the phase transition temperature. Cyclic tests revealed that the width of the hysteresis in the 2nd cycle was much smaller compared with that of the 1st cycle at room temperature. On the other hand, the difference in the stressstrain relationship and the effective compliance was hardly observed at 873 K. This result suggests that the apparent Young's modulus of the rhombohedral LSCF depends on the applied stress and the mechanical history due to ferroelasticity. Thus, the stress distribution in SOFCs can be affected by the ferroelasticity of LSCF.