The physical properties and electrochemical performance of Ca-doped Sr2MgMoO6-δ as perspective anode for solid oxide fuel cells

The double perovskites Sr 2-x Ca x MgMoO 6–δ with x = 0, 0.25, and 0.5 were obtained by combustion of organometallic precursors and were shown to have a tetragonal structure with the crystalline lattice parameters a = b = 5.569, c = 7.923, 7.899, 7.885 Å, respectively. Calcium doping was found to improve the conductivity and decrease the activation energy values. At x = 0.5, the temperature dependence of the total conductivity has a metallic-like behavior under reducing conditions. The electrical conductivity for Sr 1.5 Ca 0.5 MgMoO 6−δ was about 25 and 30 S/cm at 800 and 500 °C, respectively. Besides, the enhancement of the calcium content lead to the reduction in the area specific resistance of the Sr 2− x Ca x MgMoO 6−δ anode. In conjunction with the electron paramagnetic resonance study, the experimental data on the electrical conductivity demonstrated that calcium doping is accompanied by an enhanced electron component under reducing conditions. The magnetic susceptibility revealed the coexistence of itinerant electrons and paramagnetic centers in calcium-rich molybdate Sr 1.5 Ca 0.5 MgMoO 6−δ .