Crystal Structure and Thermal Expansion Behavior of La_0.7Sr_0.3Ga_0.7Fe_0.2Mg_0.1O_3−δ at High Temperature—Effect of Chemical State of Fe and Oxygen Nonstoichiometry—

Abstract

Crystal structure and thermal expansion behavior at high temperatures of La_0.7Sr_0.3Ga_0.7Fe_0.2Mg_0.1O_3−δ have been investigated. Its crystal structure was cubic without structural phase transition. At about 500°C, variation of thermal expansion due to generation of oxide ion vacancy was observed. The behavior of δ can be explained assuming that Fe valence decreased from 3.230+ to 3+ with increase of temperature and that stable phase with Fe³⁺ exists. La_0.7Sr_0.3Ga_0.7Fe_0.2Mg_0.1O_3−δ has high potential for electrolyte material for low temperature SOFC since increase of oxide ion conductivity and decrease of hole conduction by oxide ion vacancy can be expected above 500°C.