Mechanical properties of ferroelastic La0.6Sr0.4Co0.2Fe0.8O3−δ with various porosities and pore sizes

We have investigated the mechanical properties of porous La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (LSCF) under uniaxial compression. Porous LSCF samples containing polymethyl methacrylate pore former with different diameters (0.4, 1.5 and 10 µm) were examined. The porosity increases with the increase in pore former content, and it also slightly increases with the increase in pore former size. The average pore size is constant for the same size pore former regardless of the porosity, and it is smaller than the original pore former diameter. X-ray diffraction confirms that all the samples have a rhombohedral crystal structure. The samples contain ferroelastic domains and exhibit clear mechanical behavior related to the ferroelasticity under uniaxial compression. The initial modulus, critical stress and compressive fracture strength of the porous sample decrease with the increase in porosity and pore size, where the dependence on the pore size is most clear for the fracture strength. An empirical equation to estimate the fracture strength of porous LSCF is proposed.