Ordered to defect fluorite structural transition in Ce1-xNdxO2-δ system and its influence on ionic conductivity

The structural transformation from fluorite – defect fluorite – hexagonal phase on the heavily doped ceria system (Ce1-xNdxO2-δ X = 0, 25, 50, 75 and 100 mol%) has been investigated in this study. The oxygen ionic conductivity increased with dopant content till 50 mol% due to the formation of rare earth C-type superstructure defect fluorite. The co-formation of rare earth C-type structure along with the fluorite increase the anion vacancies and facilitates the barrier free ion migration. The long-range ordering and the existence of mixed phases in the heavily doped (75 mol%) system lowered the oxide ion conductivity. Ce0.5Nd0.5O1.75 in disordered fluorite structure exhibits a superior ionic conductivity of 6.0 mS/cm with an activation energy of 0.93 eV which has a potential as electrolyte in solid oxide fuel cells application. [Display omitted] •The structural transformation with respect to dopant concentration have been investigated.•50 mol % Nd doped CeO2 (C50N50) shows the formation of rare earth C type structure.•C50N50 exhibited the higher ionic conductivity of 6.0 mScm−1 with 0.93 eV activation energy.