【作者】 刘晃清；

【导师】 王玲玲；

【作者基本信息】 湖南大学 ， 材料物理与化学， 2007， 博士

【摘要】 本论文主要研究ZrO₂：RE纳米材料和体相材料的发光性质与La₂O₃：RE纳米材料和体相材料的制备及发光性质，用J—O理论对其掺Eu材料光学性能进行了计算，我们获得的结论如下：两种掺杂纳米材料样品的发光与稀土的掺杂浓度、样品的制备过程以及退火温度有关。对于Eu掺杂的纳米材料，在相同紫外光的持续辐照下，不同样品的最强发射强度的变化均与紫外光辐照时间有关，而体材料没有这个现象发生。Eu掺杂的体材料的发光强度均强于其相应纳米材料的发光强度。Eu³⁺离子掺杂的两种纳米材料的发光与老化时间有关，随老化时间的延长，电荷迁移带强度变弱。两种Er³⁺离子掺杂的纳米材料均难观察到它们的激发光谱。它们的上转换发射强度在相同的测量条件下，均弱于相应体相材料的上转换发光强度。两种Yb³⁺和Er³⁺共掺杂的材料在380nm荧光激发下只有绿色发光，没有红色发光，在⁴S_3／2→⁴I_15／2的跃迁发射的绿色发光中，560nm左右的发射位置不随Yb³⁺离子浓度的变化而变化，而在545nm左右的发射位置与Yb³⁺离子浓度有关。在980nm光激发下得到的上转换发光均与Yb³⁺离子的掺杂浓度有关，Yb³⁺离子的掺杂浓度提高时，红绿上转换发射强度变化很大。利用J—O理论和发射光谱计算了ZrO₂：Eu³⁺，La₂O₃：Eu³⁺材料包括纳米材料和体相材料的Ω₂和Ω₄参数，计算并分析了电偶极和电多极相互作用引起的⁵D₀→⁷F₂跃迁的共振能量传递的速率。在低掺杂浓度下，Eu离子之间⁵D₀→⁷F₂跃迁的共振能量传递速率小于它的自发辐射速率。在低掺杂浓度下Eu离子之间的能量传递可以不用考虑。在相同的稀土掺杂条件、相同的制备方法和相同的测量条件下，La₂O₃：RE材料的发光强度远强于ZrO₂：RE材料的发光强度，即La₂O₃材料比ZrO₂材料更适宜于做发光基质材料。更多还原

【Abstract】 In this dissertation, after the investigation on the optical properties of nanocrystalline and bulk materials ZrO₂ and La₂O₃ doped with RE³⁺ ions and the calculation of the parameterΩbased on the Judd—Ofelt theory for the samples doped with Eu³⁺ ions, some conclusions taken are as follows:The optical properties of the two kinds of samples doped with RE³⁺ ions are associated with dopant concentration, preparation process and annealing temperature. To the different types of nanocrystal samples doped with Eu³⁺ ions, under continuous ultraviolet （394nm） irradiation, the strongest emission intensity change of different samples are as a function of irradiation time. However, those phenomena can not be observed in the bulk materials. In addition, under the identical conditions, the emission intensity of the bulk samples doped with Eu³⁺ ions is greater than that of corresponding nanocrystals. The fluorescent properties of the nanocrystalline samples doped with Eu³⁺ ions are related to aging time, the longer the aging time, the weaker the emission intensity. About the two kinds of nanocrystals doped with Er³⁺ ions, it is difficult for the excitation spectra to be observed. Under the identical measurement conditions, the upconversion of the nanocrystals is weaker than that of corresponding bulk materials, whose only green emission can be found under 380nm excitation in the codoped system of Yb³⁺ and Er³⁺ ions, in which the peak position at around 560nm is changeless and the peak position at about 545nm changes as Yb³⁺ ion concentration varies. Their upconversion emission intensity at 980nm excitation is strongly dependent on the Yb³⁺ ion concentration. The emission intensity ratio of green to red upconversion remarkably diversifies as Yb³⁺ ion content increases. Additionally, the parametersΩ₂ andΩ₄ are calculated on the basis of the Judd-Ofelt theory and emission spectra for the two kinds of samples doped with Eu³⁺ ion including nanocrystals and bulks. We obtained the rate of resonant energy transfer of ⁵D₀→⁷F₂ transition caused by the interaction between electric diple and electric multiple.At low dopant concentration, the rate of resonant energy transfer for the ⁵D₀→⁷F₂ transition between Eu³⁺ ions is smaller than that of its spontaneous emission. Accordingly, the energy transfer between Eu³⁺ ions can be neglected. By comparison with the optical properties of the two kinds of materials doped with identical rare earth ions, we found the emission intensities of La₂O₃:RE³⁺ was greater than those of ZrO₂:RE³⁺ under the identical conditions including dopant content, preparation methods and measurement condition, in other words, La₂O₃ is a better optical material than ZrO₂.更多还原