Characterisation of microstructure and hardness of perovskite-structured Ba0.5Sr0.5Co0.8Fe0.2O3 − δ under different sintering conditions

Microstructural evolution of Ba0.5Sr0.5Co0.8Fe0.2O3 − δ (BSCF) has been investigated using commercial powders sintered at different conditions. All the samples, characterised by the porosity P and grain size D, are determined to be a single cubic phase. The grain growth kinetics is evaluated using Dn = tK0exp(−Q/RT). Grain boundary diffusion is the dominant controlling mechanism of densification and the Ba/Sr diffusion is the rate-controlling species. Additionally, the Vickers hardness (HV) of BSCF is measured at ambient condition. The HV is successfully described by an exponential function of porosity, HV = H0exp(−bP). The porosity is the dominant factor determining the hardness when it is over 0.06. Otherwise, the Vickers hardness shows a dependence on pore size. Compared with the strong dependence of hardness on porosity, no correlation between hardness and grain size or grain orientation has been found.