Preparation and characterization of a ZnO powder with the hexagonal plate particles

Zinc oxide precursors were obtained by the reaction of excess urea with 0.05–0.30 M ZnSO4 in boiling aqueous solution. The precursors precipitated were dried at 100 °C for 2 h to yield powdery products and these products were calcined at 1000 °C for 2 h to yield zinc oxide powders. Differential thermal analysis (DTA) and thermal gravimetric analysis (TGA) curves of the air-dried precursor precipitates show that the suitable temperatures for dehydration of crystal water, of ligand water and of dehydroxylation are 76, 290, and 866 °C, respectively. From the scanning electron microscopy (SEM) photographs and particle size distribution (PSD) curves, the average sizes of the hexagonal plate particles in precursor and ZnO powders are found to be 55 and 35 μm, respectively. X-ray diffraction (XRD) data were evaluated by Scherrer equation for the estimation of the average crystal size of the precursor (11 nm) and ZnO (45 nm). The specific surface area and specific micro-mesopore volume of the ZnO powders are so small as to fall into the experimental error limits. It was concluded that all the measured quantities are not affected considerably by the Zn2+ concentration.