微量Co2+掺杂ZnO粉体的结构和光学性能研究

采用球磨法制备了Zn1-xCoxO(x=0,0.004,0.008)纳米粉体,分别利用XRD,PL光谱和紫外-可见吸收光谱对样品进行了表征。XRD图谱显示样品呈六方纤锌矿结构,随着Co2+离子掺杂量的增加,晶格常数和平均晶粒尺寸略有减小。在PL光谱上观察到三个发光带:370nm处的本征发光峰、468nm附近的强蓝光发光峰,以及533nm附近的绿光发光峰。和球磨样品相比,1 200℃退火的样品的发光强度明显增强,这归因于退火使样品晶粒长大。在紫外-可见吸收谱上可以观察到两个吸收带:由ZnO的带隙吸收引起的360～388nm的强紫外吸收带和由Co2+离子的d-d跃迁引起的565nm附近的可见光吸收带。因此通过调节Co2+掺杂量和选择适当的退火温度可制备高质量的发光材料。

Structure and Optical Properties of Small Amount Co2+-doped ZnO Powder

Zn1-xCoxO(x=0,0.004,0.008) nanopowders were prepared with the method of ball milling.The samples were characterized by means of XRD,photoluminescence(PL) and UV absorption spectra.The XRD patterns show the hexagonal wurtzite structure of the samples.Upon increasing Co2+ incorporation,both lattice constants and average grain size decrease slightly.PL spectra show three emission bands: an ultraviolet emission band at 370 nm,strong blue emission bands at 468 nm and a weak green emission at 533 nm.Compared with the samples prepared by ball milling,the samples annealed at 1 200 ℃ exhibit an enhancement of luminescence intensity,which is ascribed to an increase of grain size after annealing treatment.Two bands of absorption are observed in UV absorption spectra.The strong absorption band in the ultraviolet region from 360~388 nm is ascribed to the band gap absorption of ZnO,and the weak absorption band in the visible region 560 nm results from the Co2+ d-d internal transitions.Therefore,high-quality luminescence materials can be prepared by adjusting the amount of Co2+-doped and selecting the appropriate annealing temperature.