The present work is intended to understand atomic scale mechanism of oxy-ion conduction in co-doped ceria system. The role of aliovalent dopant pairs on oxygen vacancies generation, clustering and dissociation mechanism in ceria system are probed by EXAFS, XANES and Raman spectroscopy. Correlation between atomic positional shift, oxygen vacancy defects, and oxide ion conductivity in doped ceria system are established from X-ray diffraction (XRD) and Raman spectroscopy study at operating temperature (300–600oC) of Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC).
The Raman spectroscopy study shows additional vibration modes related to ordering of defect spaces and generated due to association of oxygen vacancies and reduced cerium or dopant cations site, which disappear at high temperature; indicating oxygen vacancies dissociation from the defect complex. The experimental evidences of cation-anion positional shifting and oxygen vacancies dissociation from defect complex in the IT-SOFC operating temperature are discussed to correlate with activation energy for ionic conductivity.
To establish a correlation between atomic level structural changes (coordination number, interatomic spacing) formation of dimer and trimer type cation-oxygen vacancies defect complex (intrinsic and extrinsic) and dissociation of oxygen vacancies from defect cluster are closely monitored by EXAFS and XANES. It is a strategic approach to understand key physics of ionic conductivity mechanism in order to reduce operating temperature of electrolytes for intermediate temperature (300–450oC) electrochemical devices for the first time.