Evaluation of the Oxygen Migration Energy in Doped Ceria by Terahertz Spectroscopy

We measure the terahertz conductivity of doped ceria by terahertz time-domain spectroscopy at different temperatures to characterize the shape of the potential associated with microscopic ion hopping. The experimental results for Gd-and La-doped ceria show that the activation energy in doped ceria is larger than that in stabilized zirconia. This result can be explained by a simple rigid-body model with the assumption of doping-induced lattice expansion, i.e., by considering the gap between cations. Our results for conventional fluorite-type solid-oxide electrolytes show that terahertz spectroscopy can be used to investigate fast microscopic ionic conduction in various electrolytes, which cannot be accessed through conventional impedance measurements.