Charge carrier dynamics in Gd–Y co-doped nanocrystalline ceria corroborated with defect interactions

Abstract

Defect associates and their interactions with charge carriers, influencing the ion dynamics have been discussed for Gd³⁺ and Y³⁺ co-doped nanocrystalline ceria. Detailed Rietveld analysis of the X-Ray Diffraction data confirmed the single phase cubic fluorite structure of the compositions with the space group Fmm. An overall increase of the lattice parameter with Gd³⁺ ion concentration has been found. Grain and specific grain boundary conductivity have been evaluated from the complex impedance plots. A higher value dielectric constant has been observed for a co-doped sample at 20 mol% doping concentration. The interaction between dopant cations with oxygen vacancies has been found to form different defect associates and defect clusters. The association energy of co-doped samples at a 20 mol% doping concentration is observed to be a minimum in comparison with the singly doped samples of the same concentration. It has also been found that different defect clusters have a significant role on ionic conduction. The correlation among structural parameters, dielectric and conductivity responses has been discussed and established.