Double-Dopant induced local structural changes and ionic conductivity of doped ceria system: As solid electrolytes for electrochemical devices

Abstract

Present study is focused on double-dopant effect on local restructuring, oxygen vacancy defect clustering and ionic conductivity of doped ceria system. As compared to single dopant double-doping gives more flexibility in tuning ionic conductivity of ceria. Singly and double-doped ceria system (viz Ce0.85Sr0.15O2-d (SRDC), Ce0.85Sm0.15O2-d (SDC) and Ce0.85Sr0.075Sm0.075O2-d (SSRDC)) has been discussed. Fluorite structure is confirmed by X-ray diffraction (XRD) and data is well fitted using Rietveld refinement by Full-Prof suite. The electrical properties of all gas tight dense pellets of doped ceria system were investigated by Impedance spectroscopy at intermediate operating temperature range. Double-doped ceria system exhibits one order higher conductivity then single once. To explore dopant induced local structural changes in ceria EXAFS and RAMAN spectroscopy study has been carried out at operating temperature. Formation of defect cluster at room temperature and dissociation of oxygen vacancies from defect cluster are revealed from the spectroscopy data. Local restructuring is closely associated with oxygen vacancies dissociation and activation energy and thus ionic conductivity.