Co-doping effects of Y3+ and Sc3+ on the crystal structures, nanoparticle properties and electrical behavior of ZrO2 solid solutions prepared by a mild urea-based hydrothermal method

摘要

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 m(2) 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 degreesC for 24 h and then at 180 degreesC 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 degreesC, 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 degreesC, 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+. [References: 41]