Effect of heat treatment on the phase transformation, size and morphology of zirconia nanopowders synthesized via a sol-gel process

In this paper, zirconia (ZrO2) nanopowders synthesized via a sol-gel process was investigated at different temperatures. The formed zirconia powders were characterized using BET surface area (SBET) analyzer, Fourier transformer infrared (FT-IR) spectroscopy, thermogravimetric/differential thermal analysis (TG/DTA), X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The results showed that this route led to the formation of tetragonal zirconia phase (t-ZrO2) with high crystallinity at 800 ºC, then the formed tetragonal phase was transformed to monoclinic zirconia phase (m-ZrO2) at temperatures ranging from 800 to 1200 ºC. The SBET analyzer results revealed that BET surface area of the calcined nanopowders decreased with increasing the heat treatment temperature and consequently increased in the average particle size. Microstructural characterization by SEM depicted that the morphology of the synthesized zirconia nanopowders have changed according to the heat treatment history.