New pyrochlore solid solutions, which exhibited O-ion conduction due to structural disorder, were investigated. The ionic conductivity and structural disorder were analyzed here by fitting the conductivity, as a function of O partial pressure and temperature, to a defect chemical model which was based upon O Frenkel disorder. Samples of Gd2(GaSb)0.2Zr1.6O7 exhibited an ionic conductivity of 0.00214S/cm at 1000C; with an associated activation energy of 0.51eV. The Frenkel-disorder enthalpy was found to decrease rapidly with increasing Zr content, and fell to essentially zero in the case of Gd2(GaSb)0.2Zr1.6O7. The O-vacancy mobility was found to increase with the Zr content. This, together with an increase in carrier density, led to a very sharp increase in ionic conductivity at higher Zr contents.

Ionic Conductivity of Gd2GaSbO7-Gd2Zr2O7 Solid Solutions with Structural Disorder. H.Takamura, H.L.Tuller: Solid State Ionics, 2000, 134[1-2], 67-73