Structural and ionic conduction study of Sm–Pr co-doped ceria electrolyte materials for LT-SOFC applications

Abstract

Samarium praseodymium (Sm–Pr) co-doped ceria was synthesized by the co-precipitation technique as an electrolyte for low-temperature solid oxide fuel cell (LT-SOFC) applications. The structural, morphological, compositional, and electrical characterization of the synthesized samples were evaluated via x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX) and impedance spectroscopy. The generation of a single-phase fluorite structure of co-doped ceria without any secondary phases has been verified by XRD analysis, exhibiting the successful incorporation of Sm and Pr ions into the ceria lattice. Vegard's law is utilized for Pr redox behavior explaining the variation in lattice constant values. SEM pictures show that the co-doped ceria powder has a homogeneous and well-dispersed microstructure, and has enhanced particle size. The impedance spectroscopy results indicate that Sm–Pr co-doped ceria has much higher ionic conductivity than single-doped ceria. The highest amount of ionic conductivity (σionic) for the composition Ce0.80Sm0.10Pr0.10O2−δ recorded as 2.12×10−2S/cm at 500°C, and 6.19×10−2S/cm at 750°C with the lowest activation energy Ea=0.48eV, which has been not reported earlier. Sm and Pr are chosen as dopants because of their capacity to generate oxygen vacancies and improve ceria's ionic conductivity. This study contributes to the enhancement in the ionic conductivity of co-doped ceria by co-precipitation technique and the temperature-dependent frequency exponent factor "s" is also explored to comprehend the conduction mechanism of the prepared samples.