Synthesis and electrical properties of co-doping with La~(3+) , Nd~(3+) , Y~(3+) , and Eu~(3+) citric acid-nitrate prepared samarium-doped ceria ceramics

摘要

Fluorite oxides Ce_(0.8)Sm_(0.1)Ln_(0.1)O_(1.9) (denoted as SDC for singular doping and LnSDC for Ln=La, Nd, Y and Eu), were prepared by the citric acid-nitrate combustion reaction to act as electrolytes for intermediate-temperature solid oxide fuel cells (IT-SOFC). The thermal decomposition, phase identification, morphology, density, particle size distribution and electrical properties of the samples were studied by TGA/TDA, XRD, SEM, the Archimedes method, a laser size analyzer and Impedance spectroscopy, respectively. All crystallite powders that calcined at 800 °C had a cubic fluorite structure;;the average crystallite size was between 63 and 68.5 nm. The pellets were then sintered at 1400 °C in air for 7 h. The relative densities of these pellets were over 95%, which was in good agreement with the results of the SEM. The impedance measurements were performed in an open circuit using two electrode configurations. The results showed that Ce_(0.8)Sm_(0.1)Ln_(0.1)O_(1.9) had the highest electrical conductivity, σ_(700°c) equal to 6.59 × 10~(-2) Scm~(_1) and the lowest activation energy equal to 0.85 eV. It was therefore concluded that co-doping with the appropriate rare-earth cations can further improve the electrical properties of ceria electrolytes.