高分子网络凝胶法制备ZnO超细粉体及其光学性能

采用高分子网络凝胶法制备球形ZnO超细粉体。通过聚乙烯醇(PVA)亚浓溶液交联网络的空间位阻作用,经过烧结,获得了具有球形形貌的粒径为1~3μm的ZnO粉体颗粒。利用X射线衍射(XRD)、扫描电镜(SEM)分析了不同PVA浓度以及退火温度对产物形貌、结构的影响,发现在PVA溶液浓度为5%,并且经500℃热处理所形成的ZnO球形颗粒最为均匀规整。研究了球形ZnO粉体的光致发光性能,室温下经325nm波长激发,观察到两个中心波长分别位于407,468nm的微弱的荧光发射带,在合适温度下,在385nm处还出现了较强的紫外峰。PL光谱表明,退火温度对ZnO的光致发光影响较大,随着退火温度升高,由于表面缺陷和结晶性能发生变化,407nm处发射峰逐渐减弱消失,而紫外发光先增强后减弱,经500℃热处理样品的紫外发光性能达到最佳。

Synthesis of Spherical ZnO Ultrafine Powder by Polymer Network Gel Method and Photolumineseence Spectrum Characters

Micrometer-sized spherical ZnO ultrafine powder was prepared by polyvinyl alcohol gel method. Zinc acetate was used as starting material,polar polymer polyvinyl alcohol with long chain was used as grids localization and lattice reagent to control nucleation and crystal growth via ionic complexation between the hydroxy groups and Zn²⁺ ions. The products were obtained by changing thermal treatment under controlling rise rate. The as-prepared ZnO powder was characterized by X-ray diffraction (XRD), scanning electron micro-scopy (SEM) and photoluminescence (PL) spectra. The analytical results of SEM and XRD indicate that the concentrations of the PVA solution, sintering temperature are the factors influencing the preparation. It is found that the uniform spherical ZnO with diameter about 1~3 μm are obtained under the conditions of a PVA concentration of 5% and sintering temperature of 500℃ at which most of polymer are removed after 3 h.The PL spectra of these samples include two blue emission peaks, centered at 407 nm which is attributed to the zinc vacancies and 468 nm which is due to the transition of electrons from the level of the ionized oxygen vacancies to the valence band at room temperature when excited with 325 nm light. The ultraviolet emission peak located at 385 nm which originates from the interband transition of electrons has been observed at certain temperature. It is found that the intensities of these peaks vary with annealing temperature. With increasing the heat treatment temperature, the blue emission peak at 407 nm gradually disappears. The intensities of ultraviolet emission peaks are sharply enhanced and approach a maximum value for the sample prepared at 500℃, then it decreases as the annealing temperature increase up to 600℃.