Grain size-dependent electrical conductivity in scandia-stabilized zirconia prepared by a mild urea-based hydrothermal method

Weakly agglomerated nanocrystalline (ZrO2)0.92(Sc2O3)0.08 (8ScSZ) powders (6.7 nm in size) in fluorite cubic structure were synthesized by a two-step hydrothermal process in the presence of urea: a stock solution containing metal nitrates and urea was heated at 80 °C for 24 h and then at 180 °C for 48 h. Dense 8ScSZ ceramic samples with grain sizes ranging from 60 nm to 6 μm were fabricated by isostatically pressing the as-prepared powders followed by sintering at 1000–1400 °C. The bulk conductivities of the samples were considerably higher than those reported in the literatures especially at low temperature range. A significant enhancement of the specific grain boundary conductivity was also found when the grain size was reduced to the nanometer regime.