Microwaves (MW) are increasingly used in chemical synthesis since: 1) they permit to heat materials and fluids faster than this is possible by conventional heating, 2) high purity of the reaction is easier to achieve, since the reacting substrates can be enclosed in a vessel made of a chemically resistant material and 3) the reaction path may by modified comparing to conventional reactions.
Properties of zirconia and Pr-doped zirconia nanopowders strongly depend on shape, grain size, grain size distribution and phase composition. Also the phase composition (relative fraction of the monoclinic and tetragonal phase) depends on the synthesis conditions. The microwave driven hydrothermal synthesis permit to precisely control the reaction regime and in consequence provide to expected properties of the resulting nanocrystalline powders.
In this work we investigated the effect of process parameters on Grain Size Distribution (GSD). The GSD was determined using two methods. The first one was based on analysis of images of the nanopowders obtained by means of transmission electron microscopy (TEM). The second one was based on analysis of the shape of X-ray diffraction (XRD) peaks. The two methods yielded identical results. In addition, the XRD based method permitted to perform a phase analysis of the powders and determine separately the GSD in the monoclinic and tetragonal phase and provide some information about the shape of the grains. Therefore, this method can be recommended for the determination of the GSD, which is a crucial parameter in the technology of nanocrystalline materials.