Weakly agglomerated nanocrystalline (ZrO2)0.92(Y2O3)0.08 − x(Sc2O3)x
(x = 0–0.08) powders (8.4–9.9 nm in size) in a cubic structure with high surface area (145–153 m2 g−1) were synthesized by a two-step hydrothermal process in the presence of urea: a stock solution of metal nitrates and urea was heated at 80 °C for 24 h and then at 180 °C for 48 h. The co-doping effect of Y3+ and Sc3+ ions on the crystal structures, nanoparticle properties (crystallite size, surface area and microstrain), and sintering and electrical behaviors of the (ZrO2)0.92(Y2O3)0.08 − x(Sc2O3)x solid solutions were systematically investigated by means of X-ray diffraction and transmission electron microscopy combined with energy dispersive X-ray analysis, scanning electron microscopy, BET specific area analysis and ac impedance spectroscopy. The lattice parameter and average crystallite size of the as-prepared nanocrystallites tend to decrease with increasing scandia content. In the Arrhenius plots over the measurement temperature range of 400–800 °C, a curvature towards higher activation energy with decreasing temperature appears, which is remarkable for the compacted sample doped with 8 mol% Sc2O3
(yttria-free) after sintering at 1400 °C, although not for those doped with 8 mol% Y2O3
(scandia-free) and with 1–7 mol% Sc2O3. When scandia is substituted by yttria, the lattice conductivity decreases monotonically due to the difference in the sizes of Y3+ and Sc3+.
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