Grain boundary blocking of ionic conductivity in nanocrystalline yttria-doped ceria thin films

Nanocrystalline YDC thin films with grain-sizes ranging from 38 to 93-nm were prepared using pulsed laser deposition followed by thermal annealing. Ionic conductivity decreased up to four orders of magnitude as the grain size increased. Using energy-dispersive X-ray spectroscopy, we showed that the counter-intuitive reduction in conductivity with grain-size is likely due to dopant and impurity segregation near grain-boundaries. Spectroscopic evidence suggests that the blocking effect due to defect segregation is more dominant on ionic conductivity than the grain-sizes.