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采用共沉淀法制备了ZnS及ZnS∶Eu纳米晶粉末 ,并对其在不同温度进行了退火处理。通过X射线粉末衍射 (XRD)技术及差热分析实验 (DTA)对ZnS纳米粒子在退火过程中的从立方到六角晶相的结构相变进行了研究。实验结果表明 ,同体材料相比 ,由于ZnS纳米晶具有较大的表面活性 ,其相变温度大大降低了。在由纳米粉末退火制备的样品中 ,观察到峰值位于 460nm和 5 2 0nm的两个发光带。前者是ZnS的自激活发光 ;后者归因于纳米晶制备过程中引入的缺陷或者在退火过程中形成了杂质能级。在退火温度低于 80 0℃条件下 ,由纳米粒子制备的样品和由商用生粉制备的荧光粉相比较 ,前者的发光明显较强。铕的掺杂并没有形成新的发光中心 ,但却极大的增强了ZnS的缺陷发光。
ZnS and ZnS:Eu nanocrystalline powders were prepared by coprecipitation method and annealed at different temperatures. The phase transition from cubic to hexagonal phase of ZnS nanoparticles during annealing was investigated by X-ray powder diffraction (XRD) and differential thermal analysis (DTA). The experimental results show that the phase transition temperature of ZnS nanocrystals is much lower than that of bulk materials due to their large surface activity. In the samples prepared by nano-powder annealing, two luminescent bands with peaks at 460 nm and 520 nm were observed. The former is a self-activating luminescence of ZnS; the latter is due to defects introduced in the nanocrystalline preparation process or formation of impurity levels during annealing. The luminescence of the former was obviously stronger than that of the phosphor prepared from commercial raw powders when the annealing temperature was lower than 80 0 ℃. The doping of europium did not form a new luminescent center, but it greatly enhanced the defect luminescence of ZnS.