Room-temperature synthesis and conductivity of the pyrochlore type Dy ₂(Ti_1-yZr_y)₂O ₇ (0≤y≤1) solid solution

Different compositions in a solid solution of general formula Dy ₂(Ti_1-yZr_y)₂O ₇, showing high oxygen ion conductivity, have been successfully prepared at room temperature via mechanochemical synthesis. Stoichiometric mixtures of the constituent oxides were dry milled together in a planetary ball mill by using zirconia vials and balls. Chemical changes in the powder mixtures as a function of composition and milling time were followed by X-ray diffraction and revealed that, in all cases and after milling for 19 h, the powder mixtures consisted of a single phase. Electrical properties were measured on sintered pellets as a function of frequency, temperature and zirconium content, revealing an increase in conductivity of more than one order of magnitude for y≥0.4, which, as observed in the similar Y₂(Ti_{1- y}Zr_y)₂O₇, has been related with the onset of disordering of the anion sublattice. Despite increasing structural disorder with increasing Zr content, conductivity remains almost constant for y>0.6, reaching a maximum value of ∼5×10^-3 for Dy ₂Zr₂O₇ at 900 °C.