The effect of an oxygen partial pressure gradient on the mechanical behavior of perovskite membrane materials

In application of perovskite as oxygen conducting materials the membrane is operated at elevated temperatures under an oxygen gradient. The effect of the partial pressure difference on the mechanical properties is reported in the current work. Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) and La0.58Sr0.4Co0.2Fe0.8O3−δ (LSCF) samples were annealed under an oxygen gradient. The mechanical properties of cross-sections were characterized using indentation testing. Chemical strains for BSCF and LSCF were too small to detect them after cooling to RT by XRD; however, the results suggest that the indentation crack length is affected by chemical strains for LSCF, but not for BSCF. An anisotropy of the indentation crack length and corresponding apparent fracture toughness is related with the interaction of domain switching and residual strain that is probably also associated with the observation that vacuum (10−5 mbar) annealed LSCF showed surface cracking on heating in air, whereas for BSCF such fracture features were not observed.