Yttria-based nano-sized powders: A new class of fractal materials obtained by combustion synthesis

摘要

Small-angle x-ray scattering (SAXS) techniquehas been used to investigate nano-sized powders of Y_2O_3,Y_(1.8)Er_(0.2)O_3, and Y_(1.8)Nd_(0.2)O_3, obtained bymeans of combustion synthesis. The results show that thepowders have a mass-fractal behavior, with fractal dimension,D_f, in the 1.7-1.8 range, and average particle sizes in the 20-30-nm range. These results are supported by transmissionelectron microscope observations. Moreover, from SAXS data,it has been possible to establish a narrow particle sizepolydispersity, as well as the presence of particle-diffuse or"fuzzy" interfaces. These results show, for the first time, thefractal behavior of materials prepared by combustion synthesisand are in agreement with a recently developed model. Thenanostructural features are discussed within the framework ofthe peculiar optical properties of the doped luminescent materials.