Sintering of nanostructured Sc2O3 ceramics from sol-gel-derived nanoparticles

Sol-gel route was used to synthesize scandium oxides nanopowders. Oxohydroxide nanoparticles were first prepared in solution using ScCl3 . xH(2)O as precursor. The influence of pH and reflux time on particle size and shape was studied. Sc2O3 nanoparticles were then obtained after water dialysis and ScOOH sol drying. Depending on pH, 40-1000 nm size ScOOH particles can be obtained. At a given pH, reflux time also influences the ScOOH particles size, which can vary from a few nanometers to 1 mu m. The ScOOH sol can be used to prepare very pure Sc2O3 nanopowders. Results indicate a strong relation between nanoparticle size and the transformation temperature of gamma-ScOOH to Sc2O3. A direct correlation between the Sc2O3 powder and the original ScOOH nanoparticle shapes has also been observed. From the TEM studies, it is likely that the crystallization from the phase ScOOH into Sc2O3 one is isomorphic. Spark plasma sintering test highlights a very good sinterability of the Sc2O3 powder. Nearly fully dense ceramics can be obtained at 1400 degrees C. Microstructure is very homogeneous with ultrafine grains, with size in the range of 25-225 nm. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.