Investigation of the high-temperature redox chemistry of Sr2Fe_(1.5)Mo_(0.5)O_(6-δ) via in situ neutron diffraction

摘要

Crystallographic structural changes were investigated for Sr2Fe_(1.5)Mo_(0.5)O_(6-δ), an electrode material for symmetric solid oxide fuel cells. The samples of this material were heated and cooled in wet hydrogen and wet oxygen atmospheres, to simulate the reducing and oxidizing conditions experienced under actual fuel cell operating conditions, and their structures and oxygen contents were determined using in situ powder neutron diffraction. The existence of a reversible tetragonal to cubic phase transition was established to occur between room temperature and 400 °C, both on heating and cooling in either oxygen or hydrogen. The oxygen content reaches a low value of 5.50(2) at 850 °C in wet hydrogen. Excellent correlations are observed between the oxygen content of the structure and the conductivities reported in the literature.