Microstructure and mechanical properties of Ba0.5Sr0.5Co0.8Fe0.2O3−δ perovskite-structured oxides doped with different contents of Ni

Microstructural evolution and mechanical properties of Ba0.5Sr0.5(Co0.8Fe0.2)1−XNiXO3−δ with X=0, 2, 4, 6, 8, 15, 20, and 25 mol% have been systematically investigated. The porosity increases from 4.0% to 17% with increasing the content of Ni doping from 0 to 25 mol%. Meanwhile, the grain size decreases from 22.5 to 5 µm. All the samples are indexed to be a single cubic phase when the Ni doping content is below 25 mol%. Otherwise, secondary phases (NiO) are found along grain boundaries and inside grains. Hardness and Young's modulus first increase with increasing the content of Ni doping from 0 to 8 mol% and then both decrease with the further increase in the content of Ni doping. The fracture toughness increases with increasing the content of Ni doping from 0 to 20 mol%. However, it decreases with further increasing the content of Ni doping due to the increase in porosity.