Stability of SrFeO3 based materials in the presence of SiOx species in humid atmosphere at high temperatures and pressures

Strontium silicate was found on the surface of La0.2Sr0.8Fe0.79Cr0.2Mg0.01O3 exposed to hydrogen containing humid atmospheres at 1000 C and 30 bars. Silica originated from the furnace tube material and was transported via the gas phase as a gaseous silica hydrate. Fe and Sr were initially preferentially expelled from the perovskite grain boundaries to give Sr2SiO4 at the surface, along with a secondary Fe-rich phase and a LaCrO3-rich grain boundary region. Fe and Sr were eventually drawn from the grains, leaving a porous structure. This highlights the importance of avoiding Si sources near Sr-rich membranes in humid atmospheres at high temperatures. 17 refs.