Preparation, structure and electrical conductivity of the pyrochlore-type phase Sm₂Zr₂O₇ codoped with bivalent magnesium and trivalent dysprosium cations

The pyrochlore-type phases with the compositions of SmDy _1-xMg_xZr₂O_7-x/2 (0 ≤ x ≤ 0.20) have been prepared by pressureless-sintering method for the first time as possible solid electrolytes. The structure and electrical conductivity of SmDy_1-xMg_xZr₂O_7-x/2 ceramics have been studied by the X-ray diffraction (XRD), scanning electron microscopy (SEM) and impedance spectroscopy measurements. SmDy_1-xMg_xZr ₂O_7-x/2 (x = 0, 0.05, 0.10) ceramics exhibit a single phase of pyrochlore-type structure, and SmDy_1-xMg_xZr ₂O_7-x/2 (x = 0.15, 0.20) ceramics consist of pyrochlore phase and a small amount of the second phase magnesia. The total conductivity of SmDy_1-xMg_xZr₂O_7-x/2 ceramics obeys the Arrhenius relation, and the total conductivity of each composition increases with increasing temperature from 673 to 1173 K. SmDy_1-xMgxZr ₂O_7-x/2 ceramics are oxide-ion conductors in the oxygen partial pressure range of 1.0 × 10^-4 to 1.0 atm at all test temperature levels. The highest total conductivity value is about 8 × 10^-3 S cm^-1 at 1173 K for SmDy_1-xMg _xZr₂O_7-x/2 ceramics.