Synthesis, ionic conductivity, and ageing behavior of [x Y2O3-(10 - x) Sc2O3]-90 ZrO2 (x = 2, 3, 4, and 5 mol%) as well as 10-11 mol% Sc2O3-ZrO2 electrolytes are presented. High dense homogeneous ceramic samples with fine microstructure were prepared from laser synthesized mixed nanopowders 10YSZ and 10ScSZ using low sintering temperatures of 1010-1300 degrees C. Stabilization of cubic fluorite-type phase has been achieved for Y-doped ScSZ composites at these temperatures. It is shown that the DC conductivity of the Y-doped ScSZs decreases proportionally to the yttria content throughout the temperature range studied, from 500 to 900 degrees C. Ageing behavior of the electrolytes was studied at 850 degrees C for 1200-2700 h. Low resistivity degradation of Y-doped ScSZ not exceeded 10% during extended annealing for 2700 h has been obtained for the samples sintered below 1100 degrees C. High and stable conductivity has been obtained for 10ScSZ and 11ScSZ. Any decrease in their conductivity during extended annealing was not detected. (C) 2012 Elsevier B.V. All rights reserved.