Preparation,characterization and electrical property of Mn-doped ceria-based oxides

Manganese-doped ceria-based oxides, Ce_1?xMn_xO_2?δ (0.05 ≤ x ≤ 0.3) and Ce_1?x?yGd_xMn_yO_2?δ˙ (0.05 ≤ x≤ 0.2, 0.05 ≤ y ≤ 0.25) were synthesized, and crystal phase analysis by XRD and measurements of electrical properties were performed. Solubility limit of Mn in Ce_1?xMn_xO_2?δ˙ seemed to be between 5 mol% and 10 mol% and Mn₃O₄ was the main by-product above the solubility limit in the case of heat treatment at 1300 °C. Judging from the oxygen partial pressure dependence of total conductivity and emf measurements, Ce_1?xMn_xO_2?δ˙ is a single-phase mixed conductor within the composition below the solubility limit, and when the composition of Mn exceeds the solubility limit, it becomes the dual-phase mixed conductor of Ce_1?xMn_xO_2?δ˙ and Mn₃O₄. The doing of Mn in gadlia-doped ceria, Ce_1?x?yGd_xMn_yO_2?δ˙ (0.05 ≤ x ≤ 0.2, 0.05 ≤ y ≤ 0.25), was more difficult than that in CeO₂ presumably due to the preferential reaction between Gd and Mn to give GdMnO₃ to the GDC solid solution formation, and the Mn doping seems not to be so effective in preparing the mixed ionic–electronic conductor based on GDC.