Impedance Spectroscopy Analysis of Zirconia:10 mol% Scandia Solid Electrolytes During and After Sintering R. Muccillo, and G. C. C. Costa CMDMC - Center of Science and Technology of Materials, Energy and Nuclear Research Institute, Cidade Universitária, S. Paulo, SP 05508-900, Brazil ZrO 2 :10 mol%Sc 2 O 3 (10ScSZ) powders were synthesized by the polyacrylamide technique (route I) and the polymeric precursor technique (route II). Attrition milling was used to break up powder agglomerates. The evolution of the distribution of particle size upon attrition milling was evaluated by laser scattering. Impedance spectroscopy measurements were carried out in cold-pressed powders in the 500 C-1400 C range during sintering and in the 300-500 C range after sintering. Upon sintering, the decrease of the total electrical resistivity of the specimens prepared with both powders is similar. Nanosize ZrO 2 :10 mol% Sc 2 O 3 powders synthesized by route I are less sinteractive than powders synthesized by route II due to formation of agglomerates, which produce, upon sintering, pellets with intragranular pores. Sintered pellets using powders prepared by route I have lower electrical conductivity than pellets using powders prepared by route II. Introduction Stabilized zirconia ceramics are widely used as solid electrolytes in oxygen sensing devices and in solid oxide fuel cells (SOFCs). The most used compounds are ZrO 2 :MgO, ZrO 2 :CaO and ZrO 2 :Y 2 O 3 ceramics in disposable high temperature (1550-1600 C) oxygen sensors, in permanent (600 C) oxygen sensors and in SOFCs (900 C-1000 C), respectively. The required electrical conductivity of oxygen ions for operating a SOFC is 10 -1 S/cm. YSZ reaches this value at 1000 C. The reduction of the working temperature of SOFCs down to 600-700 C needs either the development of new solid electrolytes or somehow improving the actual ones. ZrO 2 :Sc 2 O 3 is a promising solid electrolyte for that application (1,2). The reason is that cubic ZrO 2 :Sc 2 O 3 has oxide ion conductivities at 600- 800 C similar to the ones of cubic ZrO 2 :Y 2 O 3 at 800-1000 C, allowing for designing SOFCs for operation at lower temperatures with the usual benefits (3-5). It is known that the highest ionic conductivity of the zirconia solid solutions is that of ZrO 2 :Sc 2 O 3 (2, 6- 8). Structural analysis of ZrO 2 :(7-13) mol% Sc 2 O 3 by X-ray diffraction shows two different structures, the cubic fluorite and the rhombohedral pyrochlore phase, in agreement with the phase diagram (9). Scandia-stabilized zirconia exhibits a cubic phase for scandia contents 10 mol% and shows a maximum ionic conductivity value for the 10 mol% Sc 2 O 3 -doped ZrO 2 (5). There are many other reports on the structural phases of the ZrO 2 :Sc 2 O 3 system (10-12). ECS Transactions, 13 (26) 61-73 (2008) 10.1149/1.3050378 ©The Electrochemical Society 61