The influence of pentavalent Nb substitution for Zr on electrical property of oxide-ion conductor Gd2Zr2O7

Gd2(Zr1−xNbx)2O7+x (0 ≤ x ≤ 0.2) ceramics are prepared via the solid state reaction process at 1973 K for 10 h in air. Gd2(Zr1−xNbx)2O7+x (x = 0.1, 0.2) ceramics exhibit an ordered pyrochlore-type structure, whereas Gd2Zr2O7 has a defective fluorite-type structure. The electrical property of Gd2(Zr1−xNbx)2O7+x ceramics is investigated by electrochemical impedance spectroscopy over a frequency range of 10 Hz to 8 MHz from 623 to 923 K. The electrical conductivity obeys the Arrhenius equation. The grain conductivity of Gd2(Zr1−xNbx)2O7+x ceramics varies with doping different Nb contents, and exhibits a maximum at the Nb content of x = 0.1 in the temperature range of 623–923 K. The conductivity in hydrogen atmosphere is a little bit higher than in air in the temperature range of 723–923 K, which indicates that the doping of Zr4+ by Nb5+ can increase the proton-type conduction and reduce the oxide-ionic conduction. The conduction of Gd2(Zr1−xNbx)2O7+x is not a pure oxide-ionic conductor.