Luminescent Properties in Relation to Controllable Phase and Morphology of LuBO3:Eu3+ Nano/Microcrystals Synthesized by Hydrothermal Approach

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• 作者：Yanping Li ; Jiahua Zhang ; Xia Zhang ; Yongshi Luo ; Shaozhe Lu ; Xinguang Ren ; Xiaojun Wang ; Lingdong Sun ; Chunhua Yan
• 刊名：Chemistry of Materials
• 出版年：2009
• 出版时间：February 10, 2009
• 年：2009
• 卷：21
• 期：3
• 页码：468-475
• 全文大小：296K
• 年卷期：v.21,no.3(February 10, 2009)
• ISSN：1520-5002

文摘

The calcite and vaterite type LuBO₃:Eu³⁺ nano/microcrystals with various morphologies were synthesized by the hydrothermal (HT) approach through controlling the pH values of the precursor solutions. The calcite type LuBO₃:Eu³⁺ shows the dominant magnetic dipole ⁵D₀−⁷F₁ emission due to S₆ inversion symmetry of Lu. It also shows a symmetrical O−Eu charge transfer (CT) excitation band, which, however, is asymmetrical and broad in the material prepared by the solid-state (SS) reaction method. The effect of the residual OH⁻ groups introduced in HT synthesis is discussed on O−Lu exciton annihilation and local environment distortion. Two different Eu³⁺ centers, one of which is with inversion symmetry, are observed in vaterite type LuBO₃:Eu³⁺. The HT sample with nanostructures, such as vaterite type flowerlike LuBO₃:Eu³⁺, demonstrates a red shift of the CT band and appearance of a long excitation tail at the long wavelength side of the CT band. XRD, selective excitation and fluorescence decay measurements indicate that the red shift is induced by an increase of crystal lattice parameters, and the excitation tail is responsible to the Eu³⁺ ions located at lower symmetric sites. These sites are attributed to the positions at or close to the surface of the nanostructures in the sample. As the lower symmetric sites are selectively excited, the red emission of ⁵D₀−⁷F₂ of Eu³⁺ enhanced twice relatively to the orange emission of ⁵D₀−⁷F₁, exhibiting superior color chromaticity in red for display application. The luminescence properties of interior Eu³⁺ and outside Eu³⁺ are studied and discussed in detail.