The Perovskite structured ceramic (Lax,Sr1-x)(Fey,Cr1-y)O3-δ being developed for applications in oxygen transporting membranes. The permeability of this material is limited by the number of free ions, point-defects (oxygen vacancies) and electrons in the bulk. As any ordering of these unbound particles will restrict their mobility one key issue for controlling the membrane efficiency is the formation of ordered oxygen vacancies. In particular it is very likely, that at elevated temperatures ordered micro-domains progressively grow and asymptotically reach a stable equilibrium concentration. This is consistent with the observations of Kruidhof that below a specific order-disorder transition temperature equilibrium times of 30-40 h are required to attain steady-state conditions, irrespective of the thermal history of the sample.
We investigate the formation of ordered vacancies in (Lax,Sr1-x)(Fey,Cr1-y)O3-δ by atomic resolution Z-contrast imaging and electron energy-loss spectroscopy (EELS) using a 200 keV STEM/TEM JEOL2010L with a post column Gatan Image Filter (GIF).