Crystallization kinetics and growth mechanism of 8 mol% yttria-stabilized zirconia (8YSZ) nano-powders prepared by a sol-gel process

Eight mol% yttria-stabilized zirconia (8YSZ) gel powders were synthesized at 348 K for 2 h using ZrOCl₂·8H₂O and Y(NO₃)₃·6H₂O as starting materials in an ethanol-water solution by a sol-gel process. The crystallization kinetics and growth mechanism of the 8YSZ gel powders have been investigated using differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The XRD results and SAED pattern show that the 8YSZ gel powders calcined at 773 K for 2 h is a cubic ZrO₂. The activation energy for the crystallization of the cubic ZrO₂ formation in the 8YSZ gel powders is determined as 231.76 kJ/mol by a non-isothermal DTA method. Both growth morphology parameter (n) and crystallization mechanism index (m) are close to 3.0, indicating that the bulk nucleation is dominant in the cubic ZrO₂ formation. The TEM examination shows that the cubic ZrO₂ has a spherical-like morphology with a size ranging from 10 to 20 nm.