Impact of reordering in structure of amorphous zirconia xerogel under fluoride modification on crystal kinetic crystallization and morphology

Abstract

The influence of the amount of F-agent on the characteristics of nanoparticles (NPs), instant phase stability, the NPs shape and the process of NP crystallization are discussed. The structural reorganisation in F-modified amorphous xerogel aggregates leads to the formation of anisotropic-shaped crystallites under the crystallization of such xerogel. The kinetic parameters of crystallization are estimated. It was shown the main mechanism of crystalization is crystal growth controlled by interface reaction and bulk nucleation occurs with constant number of nuclei. The change of mechanism from 3-dimensional growth for pure zirconia to 2- or 1-dimensional growth for modified systems with the increasing of F-amounts is observed. It reflects the change of the morphology of crystal from sphere for pure zirconia to parallelopipedon and needle shapes for F-modified zirconia with high F-content. The increasing of Ea value of F-modified xerogels in comprison with an unmodified system is observed.