Structure And Properties Of ZnO Synthesized By Hydrothermal Method

Zinc oxide (ZnO) is a new wide band gap semiconductor material with excellent optical and electrical properties,owning a wide direct band gap of3.37eV and a large excition binding energy of60meV at room temperature.Due to its favourable structural,oOptical and catalytic properties, zinc oxide has been widely used as gas sensors, antireflective coatings, photo catalyst, field-emission device and in solar cells. Such performances depend not only on the compose structure of the material, but also on its dimensionality and configuration. As a result, designing ZnO material’s capability and selective assembly are of practical significance for multiple applications.This work was the starting point for different forms by the hydrothermal synthesis of ZnO microstructures, the typical morphology controllable preparation, focusing on further study the relationship between the microstructure and macroscopic properties. At the same time, structures and properties of these materials were also characterized and analyzed. The main conclusions are summarized as following:(1) Microstructured ZnO have been synthesized by a simple hydrothermal approach using ZnCl2as zinc sources and N2H4·H2O as amine precursors in water-ethylene glycol solution at120℃for8h through hydrothermal method. The synthesized ZnO powders are characterized for structural properties by X-ray diffractrometer and scanning electron microscope and the optical properties are carried out through UV-Visible spectrophotometers. The X-ray diffractrometer pattern indicates the pure phase formation of ZnO. Scanning electron microscope images show that the aspect ratio of the ZnO microrod increases at the amount of N2H4·H2O ranging from0.5to1mL, but continuing to3ml, the aspect ratio of the ZnO microrods decreases due to the morphology of some samples transformed into microshuttles. Moreover, the optical band gaps calculated through UV spectroscopy are found to be increases from2.94(±0.02) to3.0(±0.02) eV for samples synthesized at different amounts of hydrazine hydrate ranging from0.5to1mL, respectively. (2) The bullet-like, nut-like and microrod flower-like ZnO microstructures have been controllably fabricated by tartaric acid (TA) assisted hydrothermal process.The structure and composition of the samples were characterized using by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, photoluminescence (PL) spectroscopy and UV-vis spectroscopy. With decrease in the molar ratio of Zn2+and TA, the peak position of the ultraviolet emission shifts slightly towards the red wavelength and the crystal quality was improved. The observed PL reveals two emission peaks centered at418nm and468nm and Raman spectrum also confirm the phase formation of ZnO. A possible growth mechanism on the formation of crystalline ZnO microstructures has been presented.(3) The discoid and short columnar morphology of ZnO microcrystalline were successfully prepared by hydrothermal method in the CO (NH2)2-N2H4·H2O system and zinc oxide powder were prepared by hydrothermal method at different reaction in the TEA-N2H4·H2O system under different temperature and reaction time, respectively. Also, the morphology and structure and optical properties of ZnO crystals were investigated by some characterization methods, such as XRD, SEM, UV-VIS DRS, FTIR and PL.et.al.