Influence of multi-step annealing on nanostructure and surface morphology of Y2O3:SiO2 powder

Y2O3:SiO2 powder was synthesized by a sol–gel method, using hydrous yttrium nitrate and hydrous silicon oxide as precursors and HCl as a catalyst. The dried samples were submitted to multi-step annealing schedule in air without applying pressure. A simple four-step annealing schedule with a final stage of about 900 °C for 6.0 h was followed. The samples of Y2O3:SiO2 nanocomposites were obtained with well defined size and shape. Structural changes of the nanocomposites were investigated by XRD, FTIR and TEM. Multi-step annealing scheme with different ramp rates and incubation times allows recovery-relaxation processes within the boundaries and leading to a concomitant linear increase of crystallite size and densification. Almost fully dense quasi-spherical cubic-yttria nanopowder has been demonstrated with an average grain size distribution of 10–40 nm; can be uniformly dispersed in silica matrix.