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

摘要

Microstructural evolution of Ba0.5Sr0.5Co0.8Fe0.2O3-delta (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 D-n = tK(0)exp(-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 (H-V) of BSCF is measured at ambient condition. The H-V is successfully described by an exponential function of porosity, H-V =H(0)exp(-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. (C) 2016 Elsevier Ltd. All rights reserved.