The effect of annealing temperature on hydrothermally grown sisal-like ZnO microstructures

This study has extensively described the fabrication and characterization of sisal-like ZnO microstructures. HMT aqueous solution containing zinc nitrate tetrahydrate as crystalline zinc source has been utilized to synthesize sisal-like ZnO samples via a controlled hydrothermal route. A variety of characterization techniques including FESEM, XRD, FT-IR, and Raman spectroscopy have been employed to investigate the effects related to varying annealing temperatures on morphological and structural properties. The FESEM observations have revealed a transition from hexagonal microrods to modified microrods and then to pointed microrods for sisal-like ZnO architectures as the annealing temperature increases. XRD results have indicated a considerably high purity for as-synthesized ZnO microstructures. The crystalline quantities of ZnO samples have been estimated using various X-ray line-broadening analysis methods including Debye-Scherrer and Williamson-Hall techniques. UV-Vis DRS measurements have been carried out to study optical properties. Results have shown improved light harvesting related to both enhanced absorption intensities and decreased band-gap energies with the increase of annealing temperatures.