Hydrothermal synthesis of crystallized nano-particles of rare earth-doped zirconia and hafnia

Hydrothermal processing where high temperature-high pressure aqueous solution or vapor was used as (a) a transfer medium of heat, pressure and mechanical energy, (b) an adsorbate, (c) a solvent and/or (d) a reagent for solid materials, is one of the potential processings in modern and near future science and technologies, particularly in the preparation of fine powders with nano-sized to submicron particles. Fine powders of ZrO2, HfO2, Al2O3. and their mixtures 15-40 nm in average size have been prepared in pure, crystalline, homogeneous, well-dispersed and isolated forms. The crystallization of HfO2-Eu2O3 amorphous co-precipitates yielded a single phase cubic solid solution Hf(1-x)EuxO(2-x/2) (x = 0.230 and 0.339) with a fluorite lattice by hydrothermal treatment at 300 degrees C under 10 MPa for 3 h. These products consist of non-aggregated, ultrafine, narrow-sized and single-crystalline particles of about 10 and 8 nm in size for 20 and 30 wt.% Eu2O3 samples, respectively. (C) 1999 Elsevier Science S.A. All rights reserved.