Low temperature phase transitions of the SrMo1-xMxO3-δ (M = Mg and Ga) perovskites

Abstract SrMo 1-x Mg x O 3-δ and SrMo 1-x Ga x O 3-δ (x = 0.1 and 0.2) compounds have been demonstrated to possess excellent properties as anode materials in SOFC. Additionally, these perovskite oxides, cubic at room temperature, exhibit low-temperature phase transitions that have been characterized by neutron powder diffraction (NPD) at 298, 200 and 2 K. Two phase transitions have been identified in both families: one to a tetragonal structure with I 4/ mcm space group and the second one to an orthorhombic Imma phase. The first one was observed near 270 K by an inflection in the magnetic susceptibility; the second one occurs between 200 and 2 K. The sequence involves a progressive increase of the (Mo,Mg)O 6 or (Mo,Ga)O 6 octahedra rotation, throughout one ( I 4/ mcm ) or two ( Imma ) of the pseudocubic axes. The magnetic properties suggest a Pauli paramagnetism for all the compounds.