Investigation of the crystallization of ZrO2 (Y2O3 3 mol %) nanopowder

The coprecipitation technique has been used to prepare ZrO2 (Y2O3 3 mol%) nanopowder. The influence of residual NH4Cl and pH value on the crystallization of ZrO2 (Y2O3 3 mol%) nanopowder have been investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), x-ray diffraction (XRD), infrared spectrometry (IR), and transmission electron microscopy (TEM) techniques. The IR spectra proved that the presence of residual NH4Cl increased the amount of the hydroxo group. This led to serious gel agglomerate and free enthalpy decrease. Therefore, the crystallization of ZrO2 (Y2O3 3 mol%) nanopowder is greatly influenced by the residual NH4Cl. While there is no residual NH4Cl, the crystallization takes place at 445 degrees C and is an exothermic process. On the contrary, with NH4Cl the crystallization takes place at 376 degrees C and is an endothermic process. However, the pH value does not influence the crystallization of ZrO2 (Y2O3 3 mol%) nanopowder.