Doping effects of Yb3+ on the crystal structures, nanoparticle properties and electrical behaviors of ZrO2 derived from a facile urea-based hydrothermal route

Weakly-agglomerated nanocrystalline (ZrO2)(1-x)(Yb2O3)(x) (x = 0.02-0.2) powders with high surface area (109-151 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. For x = 0.04-0.2, the as-derived powders were an assembly of uniform nanoparticles with well-defined edges in the size between 6.1-8.4 nm. Before and after calcination at 800 degreesC, the lattice parameters, microstrain and surface area of the (ZrO2)(1-x)(Yb2O3)(x) samples tended to increase with Yb3+ concentration; while, the average crystallite size decreased correspondingly. In the Arrhenius plots over the measurement temperature range of 400-800 degreesC, the bulk ionic conductivity of the compacts sintered at 1400 degreesC for 24 h showed a maximum value at the composition of x = 0.08 in cubic structure, with an activation energy of 0.89 eV. At 800 degreesC, sigma(b) = 0.049 S cm(-1) for x = 0.08. (C) 2004 Elsevier SAS. All rights reserved.