Nanoparticles and nanograin-sized Y-doped CeO2 ceramics

In this article we discuss the synthesis of nanoparticles and the preparation of dense nanoceramics of Y-doped CeO2. We prepared the nanoparticles by combustion synthesis and characterized the nanopowders by X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy. The good sintering properties of these nanopowders allowed us to obtain very dense ceramics of Y-doped CeO2 (> 90% theoretical density) and keep the grain size small, in some cases around 100 nm, by using sintering temperatures as low as 1250 degrees C and very short annealing times between 5 and 60 min. The microstructure of these nanoceramics was analyzed by atomic force microscopy and SEM. The most interesting feature of these nanoceramics is that the electrical measurements in N-2 (p(O2)=3.5x10(-6) atm) carried out by the four-point dc technique showed a considerable increase in total conductivity in comparison with the measurements in air or oxygen in the range 700-900 degrees C. This conductivity enhancement might be associated with the electronic contribution to the total conductivity and it is clearly higher than the ionic conductivity in the same temperature range.