Electrical conductivity of Sr₂MgMoO_6−δ for solid oxide fuel cell anodes

Abstract

A high purity powder of Sr₂MgMoO_6−δ (SMM) was synthesized by a solid-state reaction under atmosphere-controlled conditions. The powder was sintered at a relatively low temperature (1200°C) to prepare compacts with high grain boundary density. SMM is a promising anode material for solid oxide fuel cells and hence, the samples were characterized under conditions relevant to this application. The electrical conductivity values of SMM under various oxygen partial pressures (p_O2 = 10⁻¹⁵–10^4.3 Pa) over the temperature range of 300–850°C were measured by AC impedance spectroscopy. The grain boundary resistivity and bulk resistivity exhibited different oxygen-partial-pressure-dependent behavior. Electron conduction is proposed as the primary mechanism for electrical conductivity in the bulk of the sintered body of SMM under both low and high oxygen partial pressures. Electron conduction and oxygen ion conduction were found to be the primary mechanisms for electrical conductivity at the grain boundary of SMM under low and high oxygen partial pressures, respectively.