Micro- and macro-indentation behaviour of Ba0.5Sr0.5Co0.8Fe0.2O3−d perovskite

Ba0.5Sr0.5Co0.8Fe0.2O3−d (BSCF) is a candidate material for the application as oxygen separation membrane. However, the requisite mechanical reliability needs to be warranted. Indentation tests on dense BSCF yielded data for hardness, stiffness and fracture toughness up to a temperature of 340 °C. Complementary to this, the fracture toughness was also evaluated up to 800 °C based on an indentation-strength method. 200 °C, the values of all characteristic mechanical parameters decreased. At high temperatures they increased. The morphology of the indentation cracks depended on the applied indentation load. This was taken into account while selecting suitable expressions for calculating indentation toughness. The temperature dependence of the normalised fracture toughness as determined by indentation technique and indentation-strength method matched quite well. They revealed a good agreement with the temperature dependence of previously reported normalised fracture stresses. In addition to this, the effect of annealing on the mechanical properties of the material was also studied.