The effect of strontium doping on densification and electrical properties of Ce0.8Gd0.2O2-δ electrolyte for IT-SOFC application

The effect of strontium doping on densification and ionic conductivity of gadolinium-doped ceria (GDC) was investigated. Doped (Sr-GDC) and un-doped GDC green specimens were subjected to dilatometric measurements to evaluate their sintering behavior and to identify the sintering temperature regimes. XRD spectra show the crystal structure of the sintered samples to be cubic. Strontium doping has exhibited a relatively larger grain size as is evident by the microstructural characterization. AC impedance analysis exhibited a threefold increase in ionic conductivity for Sr-GDC (0.072 S/cm) in comparison to GDC (0.028 S/cm) samples which can be attributed to improved density and increased grain size, resulting in enhancement of total conductivity. Additionally, strontium doping to GDC lattice not only increases the oxygen vacancies but also decreases the lattice binding energy, leading to increase in oxygen ion mobility which is also confirmed by the lower activation energy exhibited by the Sr-GDC formulation. Our experimental results established that co-doping is very effective in identifying new materials with remarkably high ionic conductivity with substantial reduction in the cost for solid oxide fuel cell application.