Synthesis of yttrium aluminum garnet nanoparticles in confined environment II: Role of the thermal treatment on the composition and microstructural evolution

Nanoparticles of yttrium aluminum garnet (YAG, Y3Al5O12) have been obtained by thermal treatments, at several temperature in the range 400–950 °C, of the precursors synthetized via co-precipitation in water in oil microemulsion. The obtained nanoparticles have been characterized by means of X-ray Diffraction and Transmission Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy (EDS) and Select Area Electron Diffraction (SAED). Results show the phase evolution occurring to obtain not aggregated nanoparticles of YAG phase. A possible growth mechanism of YAG nanoparticles is discussed on the basis of observed particle microstructure and morphology. The results indicate that, applying this sequence of thermal treatments, the formation of the garnet phase takes place with the formation of yttria nuclei that grow preferentially in one direction. The growth takes place via two processes: at low temperature the nuclei evolve to the garnet phase by following the oriented attachment mechanism, at higher temperatures by the Kirkendall effect accounting for the morphological modification. The proposed synthesis and thermal treatments, by favoring one or the other growth mechanisms, allowed attaining a fine control on nanoparticles features thus making it useful for similar mixed oxides preparations.