The Effect of Homovalent A-site Substitutions on the Ionic Conductivity of Pyrochlore-type Gd2Zr2O7
J.A. Díaz-Guillén; A.F. Fuentes; M.R. Díaz-Guillén; J.M. Almanza; J. Santamaría; C. León. The Effect of Homovalent A-site Substitutions on the Ionic Conductivity of Pyrochlore-type Gd2Zr2O7. Journal of Power Sources (ISSN 0378-7753). 2009, Vol. 179, p. 349-2009.
<p>We evaluate in this work the effect of Gd substitution on the dc activation energy, Edc, and ionic conductivity of the pyrochlore-type gadolinium zirconate, P-Gd2Zr2O7. Several compositions with the general formulae Gd2-yLnyZr2O7 (Ln = Er3+, Y3+, Dy3+, Sm3+, Nd3+ and La3+), were prepared by mechanically milling and firing stoichiometric mixtures of the corresponding elemental oxides and their electrical properties analyzed as a function of frequency and temperature by using impedance spectroscopy. Whereas Gd substitution in P-Gd2Zr2O7 by smaller lanthanides induces a pyrochlore to fluorite phase transition, using larger dopant cations yields partially disordered pyrochlores. Despite of higher structural disorder, ionic conductivity values measured for the fluorite-type materials are lower than those observed for pyrochlores whereas activation energies for oxygen migration in the series decrease monotonically as the average size of the A cation increases.</p>
<p>We evaluate in this work the effect of Gd substitution on the dc activation energy, Edc, and ionic conductivity of the pyrochlore-type gadolinium zirconate, P-Gd2Zr2O7. Several compositions with the general formulae Gd2-yLnyZr2O7 (Ln = Er3+, Y3+, Dy3+, Sm3+, Nd3+ and La3+), were prepared by mechanically milling and firing stoichiometric mixtures of the corresponding elemental oxides and their electrical properties analyzed as a function of frequency and temperature by using impedance spectroscopy. Whereas Gd substitution in P-Gd2Zr2O7 by smaller lanthanides induces a pyrochlore to fluorite phase transition, using larger dopant cations yields partially disordered pyrochlores. Despite of higher structural disorder, ionic conductivity values measured for the fluorite-type materials are lower than those observed for pyrochlores whereas activation energies for oxygen migration in the series decrease monotonically as the average size of the A cation increases.</p>