Synthesis and characterization of Y and Dy co-doped ceria solid electrolytes for IT-SOFCs: a microwave sintering

In this communication, the electrical conductivities and thermal expansion studies of microwave sintered co-doped ceria Ce0.8Y0.2−xDyxO2−δ (x = 0, 0.05, 0.10, 0.15 and 0.20) solid electrolyte materials for intermediate temperature solid oxide fuel cells (IT-SOFCs) synthesized by sol–gel auto-combustion method were discussed. Microwave sintering at 1300 °C for 30 min was used for making dense powder compacts. The relative densities of all the samples are noticed above 95%. Raman spectrum was characterized by the presence of a very strong band near 460 cm−1, which along with X-ray diffraction (XRD) analysis ascertain the sample formation with a single-phase cubic fluorite structure. The lattice parameter values were calculated from XRD patterns. SEM images show nearly uniform grains with distinct grain boundaries. The thermal expansion coefficients (TECs) are found to vary linearly with temperature and were measured in the range from 14.15 to 13.20 × 10−6 °C−1. The investigation on total ionic conductivity (TIC) was executed with variation in dopant concentration and relative oxygen vacancies. The impedance analysis reveals that the sample Ce0.80Y0.10Dy0.10O2−δ displays the highest TIC, i.e., 7.5 × 10−3 S·cm−1 at 500 °C and minimum activation energy 0.90 eV compared to others. With the highest TIC and minimum activation energy, the Ce0.80Y0.10Dy0.10O2−δ might be the possible material as the solid electrolyte in intermediate temperature SOFCs.