Effect of Minor Additions of CeO_2 on Conductivity of Perovskites with Mixed Ionic-Electronic Conductivity

摘要

Conductivity, structure and thermochemical stability of compositions in the following series (100-x) Lao.6Sro.4CoO_(3±δ)·CeO_2 (LSCC), (100-x) La_(0.8)Sr_(0.2)MnO_(3±δ)·xCeO_2 (LSMC) and (100-x) La_(0.95)Ni_(0.6)Fe_(0.4)O_(3-δ)·xCeO_2 (LNFC), where x= 0, 2 and 10 mol%, were studied. CeO_2 has slightly higher solubility limit in La_(0.6)Sr_(0.4)CoO_(3±δ) and La_(0.8)Sr_(0.2)MnO_(3±δ) compared to La_(0.95)Ni_(0.6)Fe_(0.4)O_(3-δ), forming LSCC2 and LSMC2 single phase solid solutions. All compositions containing more than 2 mol% ceria were two phase and consisted of a perovskite constituent with rhombohedral structure and ceria with cubic structure. Small additions of CeO_2 influence the conductivity of the modified perovskites in a different way. Conductivity in the LSCC series dramatically decreased. Adding up to 10 mol % CeO_2 slightly changed the total conductivity in the LSMC series in spite of the presence of the secondary phase. The conductivity of the perovskites as a function of oxygen partial pressure (0.21-10~(-4) atm) is discussed.