Keywords: zirconia, co-precipitation, amorphous phase, phase transformation, nanopowders, primary crystallisation, crystal growth mechanisms, X-ray diffraction, transmission electron microscopy, particle formation, ultrasound, microwave heating, pulse magnetic field treatment, nanotechnology, diffusion
The mechanisms of particle formation in Y-doped ZrO2
The processes of nanopowder formation in ZrO2–3 mol.% Y2O3 system at 350–900°C obtained by co-precipitation using ultrasound (US), microwave (MW) heating and pulse magnetic field (PMF) treatment are considered. The energy estimations are made on the basis of Avrami theory for the crystallisation at 350°C and 400°C. It was stated by X-ray diffraction (XRD) methods that the primary particle size is reduced with the rising duration of calcination at low temperatures. The areas of identical orientation were found out by means of transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) with the size 3–5 times larger than the size of the primary particle. New mechanism of growth is suggested that consists in collective oriented crystallisation of particle groups. It is shown that diffusion mechanism of crystal growth prevails at temperatures above the critical one (630°C).