Synthesis and characterizations of Ce0.85(SmxNd1−x)0.15O2−δ ceramics

• The ratio of Sm3+ concentration to Nd3+ had significant effect on the electrical properties of SNDC.
• The SNDC (x = 0.6) had the highest ionic conductivity with slowest oxygen surface exchange.
• The SNDC (x = 0.6) showed the largest transference number of oxygen ions.
• Co-doping can enhance beneficial properties of SNDC.

Sm3+ and Nd3+ co-doped ceria, Ce0.85(SmxNd1−x)0.15O2−δ (SNDC) (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) was synthesized using the urea nitrate combustion method. The synthesized powders showed the single phase of a fluorite-type structure. The SNDC were sintered to over 98% of their theoretical density at1450 °C for 4 h in air. The electrical properties of these ceramics were investigated in both oxidizing (air) and reducing atmospheres (25 mol% H2 and 75 mol% N2). Ce0.85(Sm0.6Nd0.4)0.15O2−δ (SNDC (x = 0.6)) had the highest conductivity and the lowest activation energy in air, with the values of 0.018 S cm−1 and 0.527 eV at 550 °C, respectively. Furthermore, in reducing atmosphere, the SNDC (x = 0.6) showed the slowest oxygen surface exchange. In addition, characterization of SNDC at the actual solid oxide fuel cell (SOFC) operation conditions indicated that co-doped ceria materials had larger transference number of oxygen ions than singly doped ones. And among them, the SNDC (x = 0.6) had the largest value. Therefore, the ratio of Sm3+ to Nd3+ does have significant effect on the electrical properties of SNDC. And the SNDC with x = 0.6 is supposed to be the optimum composition.