Ionic conductivity in lanthanoid ion-doped BaCeLnO3 electrolytes

Conductivity measurements at intermediate temperatures and phase studies were carried out in the compositions Ba xCe1 − yGd yO3 − δ (0.8≦x≦ 1.1, 0 ≦ y ≦ 0.3) and BaxCe0.8Ln0.2O3 − δ (x = 0.975, 1.0; Ln = Nd,Sm,Gd,Dy,Yb). In BaxCe0.8Ln0.2O3 − δ, the Ba-deficient compositions (x = 0.975) showed higher conductivity than the stoichiometric ones (x = 1.0) for all the Ln. The total (bulk) conductivities had a maximum (σ = 5.5 × 10− 4 Scm− 1 at 250 °C) for Ln = Gd and x = 0.975. The σ value was nearly two times higher than that of the known stoichiometric BaCe0.8Gd0.2O3 − δ electrolyte and the best of those of known oxide ion conductors at intermediate temperatures. The Ba-deficient Ba0.975Ce0.8Gd0.2O3 − δ composition was a single phase of the monoclinic perovskite-related phase (I2/m). The high ionic conductivity is attributed to the fact that the Gd-doped composition had the largest cell volume in the Ln-doped Ba0.975Ce0.8Ln0.2O3 − δ series.