The Gd2-yLayZr2O7 Solid Solution as a New Electrolyte for High and Intermediate-Temperature SOFC's

Different compositions in the Gd2-yLayZr2O7 solid solution (0 {less than or equal to} y {less than or equal to} 1) were prepared at room-temperature, by mechanically milling stoichiometric mixtures of the corresponding oxides. We found that irrespective of their lanthanum content, as-prepared powder samples consist of single-phase anion deficient fluorite materials, although post-milling thermal treatments at 1200ºC facilitates the long-range ordering of cations and anion vacancies characteristic of pyrochlores for y {greater than or equal to} 0.4. Interestingly, activation energy for oxygen migration in the series decreases from 1.13 {plus minus} 0.02 eV (Gd2Zr2O7) to 0.84 {plus minus} 0.03 eV (GdLaZr2O7) as La-content and the RA/RB ratio increase. These results are explained in terms of weaker ion-ion interactions in better ordered and highlight the importance of structural ordering/disordering in determining the dynamics of mobile oxygen ions.