Electrical conduction and dielectric relaxation process in Ce0.8Y0.2O1.9 electrolyte system

In this work, we present the electrical conductivity and dielectric relaxation studies of 20 mol% yttria doped ceria (Ce_0.8Y_0.2O_1.9) electrolyte prepared by mechanical milling technique. The ac conductivity was found to obey the universal dielectric response at low temperatures. At high temperatures, the conductivity value estimated from the high frequency plateau agreed with the bulk conductivity (σ_b) obtained form the impedance spectra and the low frequency plateau value agreed with the grain boundary conductivity (σ_gb). Temperature dependence of σ_b and σ_gb gives the activation energies for conduction in the bulk and grain boundary. Two relaxation peaks were observed in the tan delta spectra; the high frequency relaxation peak is due to the bulk conduction and the low frequency peak result from the grain boundary conduction. The migration energy E_M and the energy required for the creation of free oxygen vacancies assisting oxide ion migration E_O is estimated from the resonant frequency and maxima of the tan delta spectra of these relaxation peaks. The sums of these two values in the low and high frequency peaks are nearly equal to the activation energies obtained from the bulk and grain boundary conductivity plot.