High Ionic Conductivity in the Pyrochlore-type Gd2-yLayZr2O7 Solid Solution (0 ≤ y ≤ 1)
J.A. Díaz-Guillén; M.R. Díaz-Guillén; K.P. Padmasree; A.F. Fuentes; J. Santamaría; C. León. High Ionic Conductivity in the Pyrochlore-type Gd2-yLayZr2O7 Solid Solution (0 ≤ y ≤ 1). Solid State Ionics (ISSN: 0167-2738) . 2008, Vol. 179 [38], p. 2160-2008.
As SOFC technology relies at present on La-based perovskites as cathode materials, we have analyzed the effect La incorporation might have in the ionic conductivity of P-Gd2Zr2O7, a pyrochlore-type fast oxygen ion conductor. Single phase powder samples with different La/Gd ratio, were prepared in the pyrochlore-type Gd2-yLayZr2O7 solid solution (0 ≤ y ≤ 1) by mechanically milling stoichiometric mixtures of the corresponding oxides. Electrical conductivity measurements were performed for different compositions by using pressed pellets sintered at 1500°C, as a function of frequency and in the temperature range from 250 to 800°C. Despite of increasing structural ordering (decreasing number of mobile charge carriers), it was found that oxide-ion conduction at intermediate temperatures is almost La-content independent for y ≤ 0.8 because of decreasing dc activation energy (from 1.13 to 0.85 eV). We show that these results can be explained in terms of weaker ion-ion interactions in better ordered structures (i.e., rich La-content), highlighting the importance of structural ordering/disordering in determining the dynamics of mobile oxygen ions.
As SOFC technology relies at present on La-based perovskites as cathode materials, we have analyzed the effect La incorporation might have in the ionic conductivity of P-Gd2Zr2O7, a pyrochlore-type fast oxygen ion conductor. Single phase powder samples with different La/Gd ratio, were prepared in the pyrochlore-type Gd2-yLayZr2O7 solid solution (0 ≤ y ≤ 1) by mechanically milling stoichiometric mixtures of the corresponding oxides. Electrical conductivity measurements were performed for different compositions by using pressed pellets sintered at 1500°C, as a function of frequency and in the temperature range from 250 to 800°C. Despite of increasing structural ordering (decreasing number of mobile charge carriers), it was found that oxide-ion conduction at intermediate temperatures is almost La-content independent for y ≤ 0.8 because of decreasing dc activation energy (from 1.13 to 0.85 eV). We show that these results can be explained in terms of weaker ion-ion interactions in better ordered structures (i.e., rich La-content), highlighting the importance of structural ordering/disordering in determining the dynamics of mobile oxygen ions.