Crystal structure and oxygen permeation properties of Sm1-xCaxFeO3 (x=0.2-0.3)

To investigate the influence of orthorhombic-based perovskite structures on oxygen permeation, this study focused on (Sm, Ca)-FeO3. The (Sm1-xCax) FeO3 (x = 0.20, 025, 0.30) samples were prepared using a conventional solid-state reaction method. The relative density of the prepared samples was larger than 95%. All the prepared samples were orthorhombic perovskites with space groups of Pbnm. The lattice volume decreased with increases in the Ca content. The tilt angles of the FeO6 octahedral decreased with increases in the Ca content. The oxygen permeation flux J(O2) values increased and the activation energy E-J for the J(O2) decreased with increases in the Ca content. The total conductivity sigma(t) value of the x = 0.25 sample was highest among the three different Ca content samples, suggesting that the oxygen vacancy formation energy decreases with increases in the Ca content from x = 0.20 to 0.30. Based on the investigation results, we assume that lower oxygen vacancy formation energy with doping with Ca ions is an important factor in improving oxygen permeation as well as ion conductive properties in the (Sm1-xCax)FeO3. (C) 2017 The Ceramic Society of Japan. All rights reserved.