Effects of cooperativity on ion dynamics in oxygen conducting Gd2Ti2−yZryO7

We analyze ion dynamics in the oxygen ion conductor Gd2Ti2−yZryO7 by impedance spectroscopy measurements. We find that electrical conductivity relaxation is well described by stretched exponentials of the form Φ(t) = exp(−(t/τ)1−n), with the fractional exponent n increasing systematically with Zr content. Increasing Zr content also leads to an increase in the activation energies for long-range ion diffusion from 0.7 to 1.0 eV. These results are explained in terms of the enhanced cooperativity in oxygen ion dynamics when increasing the concentration of mobile oxygen vacancies with Zr content.