<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Brownmillerite Ca<sub>2</sub>FeMnO<sub>5</sub> is prepared by calcination of stoichiometric amounts of CaCO<sub>3</sub>, Fe<sub>2</sub>O<sub>3</sub>, and MnCO<sub>3</sub> (1.</p> </abstract>