Solid oxide fuel cell / Perovskite / TEM / PED / Mixed ionic-electronic conductor

The crystal structure of SrCo0.7Fe0.2Nb0.1O2.72 was determined using a combination of precession electron diffraction (PED), high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and spa- tially resolved electron energy loss spectroscopy (STEM- EELS). The structure has a tetragonal P4/mmm symmetry with cell parameters a ¼ b ¼ ap, c ¼ 2ap (ap being the cell parameter of the perovskite parent structure). Octahedral BO2 layers alternate with the anion-deficient BO1.4 layers, the dif- ferent B cations are randomly distributed over both layers. The specific feature of the SrCo0.7Fe0.2Nb0.1O2.72 microstruc- ture is a presence of extensive nanoscale twinning resulting in domains with alignment of the tetragonal c-axis along all three cubic direction of the perovskite subcell.