Effect of Y2O3 addition on the crystal growth and sintering behavior of YSZ nanopowders prepared by a sol–gel process

The effect of Y2O3 (8 mol% ≤ Y2O3 ≤ 10 mol%) addition on the crystal growth and sintering behavior of yttria-stabilized zirconia (YSZ) nanocrystallites prepared by a sol–gel process with various mixtures of ZrOCl2·8H2O and Y(NO3)3·6H2O ethanol–water solutions at low temperatures has been studied. X-ray diffraction (XRD), Brunauer–Emmett–Teller specific surface area analyses (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron diffraction (ED) and dilatometric analysis (DA) have been utilized to characterize the YSZ nanocrystallites. Characterization reveals that the YSZ nanopowders are weakly agglomerated. When calcined at various temperatures for 2 h, the crystallite size increases and the surface area of the YSZ powders decreases when the calcination temperature increased from 673 to 1273 K. A nanocrystallite size distribution between 10 and 15 nm is obtained in the TEM examination, which is consistent with the XRD investigation. The activation energy for crystal growth were determined as 5.75 ± 0.68, 4.22 ± 0.51, and 5.24 ± 0.20 kJ/mol for 8, 9 and 10 YSZ precipitates, respectively. The morphology of the YSZ sintered at high temperature indicates the abnormal growth is due to the low activation energy for crystallite growth.