Synthesis, sintering and ionic conductivity of scandia-doped ceria ceramic materials obtained by different procedures

Crystalline scandia-doped ceria powders, with Ce0.92Sc0.08O2−δ and Ce0.82Sc0.18O2−δ compositions have been prepared by three different procedures: (a) mechanochemical route from the starting oxides; (b) co-precipitation of hydroxides from an aqueous solution; (c) solid state reaction between oxides. Nanopowders were only obtained from the two first routes. Isothermal sintering was carried out between 1200 and 1500 °C. Apparent density as high as 99% Dth was achieved by sintering at 1300 °C for 2 h from co-precipitated powders. Temperature was further reduced, and 99% Dth was also obtained by SPS at 950 °C of Ce0.82Sc0.18O2−δ mechanically activated powders. Sc2O3 was observed as a secondary phase for all the samples containing 18 at% Sc, whereas only traces were pointed out in the 8 at% Sc samples. Total conductivity attains lower values than those measured in other ceria solid solutions, at difference of that observed in cubic Sc-stabilized zirconia.