We analyze ion dynamics in the oxygen ion conductor Gd2Ti 2-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.
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We thank K.L. Ngai for stimulating discussions. Authors from Universidad Complutense thank financial support from MCYT and CAM. Authors from CINVESTAV-IPN thank CONACYT for financial support. K.J. Moreno thanks CINVESTAV-IPN for financial support during her stay at Universidad Complutense.