Microstructure and electrical relaxation studies of chemically derived Gd–Nd co-doped nanocrystalline ceria electrolytes

• Gd and Nd co-doped nanoceria was prepared through the citrate auto-ignition route.
• Microstructural parameters changed due to change in dopant concentration.
• The total conductivity has both the grain and grain boundary contribution.
• The dielectric relaxation was correlated with oxygen vacancies due to defect pairs.

Gd and Nd co-doped ceria nanocrystalline materials [Ce0.9Gd0.1-xNdxO1.95(0 ≤ x ≤ 0.1)] were successfully prepared through citrate–nitrate auto-ignition method. Rietveld refinement of the X-ray diffraction profiles was performed to get detailed microstructural information of the prepared samples. It had been found that with an increase of Nd concentration, the lattice parameter and average CeO bond distance increased. The average crystallite size, calculated from XRD was in good agreement with the transmission electron microscopy result. It was observed that, co-doped ceria showed slightly higher conductivity than the single doped with the same dopant concentration. The grain boundary conductivity was found to be higher than the grain interior conductivity. The increase in dielectric loss tangent value and shifting of the peak frequency with temperature indicated a thermally activated relaxation process which was found corresponding to defect pairs. The correlation between structural and dielectric properties of the samples was established.