Ionic Conductivity in Lanthanoid Ion-doped BaCeO_3 Electrolytes

摘要

Oxide ion conductivity was examined in Ba_xCe_(0.8)Ln_(0.2)O_(3-δ) (0.8≤x≤1.1; Ln=Lanthanoid). The slightly Ba-deficient compositions showed a higher conductivity than the nominal stoichiometric ones. A maximum total (bulk) conductivity (σ=5.5×10~(-4) Scm~(-1) at 250℃, σ=9.6×10~(-3) Scm~(-1) at 500℃) was found in the Ba-deficient composition Ba_(0.975)Ce_(0.8)Gd_(0.2)O_(3-δ). The a value at 250℃ was nearly two times higher than that of the known BaCe_(0.8)Gd_(0.2)O_(3-δ) electrolyte. The conductivity is the best of those of known oxide ion conductors at intermediate temperatures. The non-stoichiometric Ce_(0.8)Gd_(0.2)O_(3-δ) sample was a single phase of the monoclinic perovskite-related phase (I2/m). The high conductivity is attributed to the fact that the Gd-doped composition had the largest cell volume in the Ln-doped series. The unusual variation of the cell volume was due to a change in the portioning of the Ln ion between the B-site and the A(Ba)-site.