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 La_0.2Sr_0.8Fe_0.79Cr_0.2Mg_0.01O₃ 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. Eventually, Fe and Sr were drawn from the grains, leaving a porous structure. This investigation highlights the importance of avoiding Si sources near Sr-rich membranes in humid atmospheres at high temperatures.