【作者】 刘红涛；

【导师】 郜小勇；

【作者基本信息】 郑州大学 ， 凝聚态物理， 2014， 硕士

【摘要】 稀土发光材料在照明、显示、X射线放射检测、高能粒子探测等领域有着广泛的应用。YVO4具有优异的热学性能、化学稳定性和在紫外及真空紫外区域大的吸收截面，而且声子能量较小，因而常被用作稀土发光的基质材料。YVO4:Eu3+荧光粉由于其较高的量子产额，常被作为显示和照明器件的红粉成分，具有很高的商业价值。YVO4:Dy3+荧光粉和YVO4:Tm3+荧光粉在白光和蓝光发光领域具有很大的应用潜力。本文利用水热法在不同条件下制备出YVO4:Dy3+荧光粉，同时也制备出YVO4:Tm3+、YVO4:Dy3+/Tm3+、YVO4:Dy3+/Eu3+荧光粉。本论文对所制备的荧光粉的晶体结构特性和光学特性进行研究，研究成果和创新点主要有：(1)在不同pH值条件下水热合成YVO4:Dy3+荧光粉。结果发现在强酸和强碱条件下合成的荧光粉结晶状况较好。强碱性环境下合成棒状荧光粉的发光强度较好。Dy3+离子的掺杂会在YVO4晶格中引入新的振动模式。不同pH值下合成的荧光粉在200到350nm波段均出现了一个紫外吸收带。样品吸收边随着pH值的增大略有移动，吸收边基本在320nm附近。基质材料中的VO3-4离子基团和Dy3+离子之间存在高效率的能量传递。强碱环境有利于YVO4:Dy3+荧光粉的Y/B值减小。YVO4:Dy3+荧光粉中Dy3+离子的最佳掺杂浓度为1%。使用柠檬酸钠表面活性剂制备出球形荧光粉。但所制备的球形荧光粉含有较多的有机基团，严重影响了荧光粉的结晶情况和发光特性。通过退火得到多孔球形结构荧光粉，结晶效果显著提升。(2)随着退火温度的逐渐升高，荧光粉的结晶情况逐渐变好。同时荧光粉的激发谱中VO43-离子基团激发带逐渐发生红移。荧光粉的发射峰的强度也随着温度的升高逐渐变强。当在800oC时进行退火，得到荧光粉的效果最好。(3)在所制备的YVO4:Tm3+蓝色荧光粉中，基质材料中的VO43-离子基团和Tm3+离子之间也存在着高效的能量传递。YVO4:Tm3+蓝色荧光粉中Tm3+离子的最佳掺杂浓度为2%。(4)制备双掺杂YVO3+4:Dy/Tm3+荧光粉。通过在YVO4:Dy3+荧光粉掺入Tm3+离子，来增强其在蓝光部分的发光强度，从而使得荧光粉更接近纯白光的发射。通过调节两种稀土离子的掺杂比例，YVO4:2%(Dy3+0.2Tm3+0.8)荧光粉的色度坐标更接近纯白光发射。(5)我们发现在双掺杂YVO4:Dy3+/Eu3+荧光粉中的两种稀土离子之间存在着双向的，但效率不同的能量传递现象。其传递过程包括VO43-离子基团到Dy3+,Eu3+离子的能量传递、还有效率较高的Eu3+离子到Dy3+离子的能量传递和效率较低的Dy3+离子到Eu3+离子的能量传递。Eu3+离子与Dy3+离子之间可以通过借助吸收和发射多声子而实现非辐射跃迁的能量传递。少量Eu3+离子的掺杂可以增强Dy3+离子的发光强度，而当Eu3+离子浓度大于0.75%时，Dy3+离子的发光强度会逐渐减弱。而且在较小的Eu3+离子掺杂浓度下，荧光粉处于白光发射区。更多还原

【Abstract】 Rare earth luminescent materials have a wide range of application in the field oflighting, display, X-ray radiation detection, and high-energy particle detection. YVO4has excellent thermal property, chemical stability, and a large absorption cross-sectionin the ultraviolet and the vacuum ultraviolet regions. In addition, its phonon energy issmall; thus, YVO4is often used as a photoluminescent matrix material. TheYVO34:Eu+phosphor exhibits a high quantum yield. This material, which often actsas the pink ingredient of display and lighting devices, has high commercial value.YVO4: Dy3+phosphor and YVO4:Tm3+phosphor has great potential in the field ofwhite and blue light emitting. The hydrothermal method was used to synthesizeYVO4:Dy3+phosphors as well as YVO4:Tm3+, YVO4:Dy3+/Tm3+, YVO4:Dy3+/Eu3+phosphors. In this paper, the structure and optical properties of the synthesizedphosphors are studied in detail. The main findings and innovations are listed asfollows:(1) YVO4:Dy3+phosphors were synthesized under different pH conditions. It isfound that the phosphors synthesized under strong acid and alkaline conditions arewell crystallized. The rod-like phosphors synthesized under strong alkaline conditionhave preferably luminescent properties. The doping of the rare-earth ions Dy3+in theYVO4crystal lattice introduces new vibration modes. The phosphors synthesizedunder different pH values have a UV absorption band from200to350nm. Theultraviolet absorption edge moves slightly with increasing pH and is maintained atapproximately320nm. The VO43+groups in the matrix material and the rare-earthions Dy3+have efficient energy transfer efficiency. A strong alkali environment isfavorable for the decrease of Y/B value of YVO4:Dy3+phosphors. The optimal dopingconcentration of Dy3+ions is1%for the YVO4:Dy3+phosphor. The YVO4:Dy3+spherical phosphors were synthesized by using sodium citrate as surfactant. However,the phosphors contain many organic groups, and seriously affect the crystallizationand emission characteristics of the phosphors. The porous specrical phosphors wereobtained after the anealing, and the crystallization of the phosphors improved significantly.(2) As the annealing temperature gradually increases, the crystallization of thephosphors becomes better. Meanwhile, the excitation band of VO3-4groups occursredshift gradually. With annealing temperature increasing, the emission characteristicsof the phosphors also become better. When the temperature annealing reaches800oC,the best emission characteristics of the phosphors were obtained.(3) The efficient energy transfer between the matrix material VO43-groups andTm3+ions also exist in the synthesized blue YVO4:Tm3+phosphors. The optimaldoping concentration of Tm3+is2%.(4) The double-doped YVO4:Dy3+/Tm3+phosphors were synthesized. DopingTm3+ions in YVO4:Dy3+phosphor enhances its blue emission intensity of thephosphor and obtains the white light-emitting phosphor. Finally, the chromaticitycoordinates of YVO4:2%(Dy3+0.2Tm3+0.8) phosphor is closer to the whitelight-emission region.(5) It is found that a reversible but different efficient energy transfer existsbetween two kinds of rare earth ions in the YVO4:Dy3+/Eu3+phosphors.The energytransfer from VO3-4groups to Dy3+/Eu3+ions, from Eu3+ions to Dy3+ions as well asfrom Dy3+ions to Eu3+ions are coexistence in the double doped YVO4:Dy3+/Eu3+phosphors. The efficiency of energy transfer from Eu3+ions to Dy3+ions is muchhigher than that from Dy3+ions to Eu3+ions. By means of multi-phonon absorptionand emission, Eu3+ions and Dy3+ions can achieve energy transfer throughnon-radiative transition. A small number of Eu3+ions can enhance the luminousintensity of Dy3+ions. When the concentration of Eu3+ions is more than0.75%, it canweaken the luminescence intensity of Dy3+ions. The emission of the phosphors isstill in the white light-emitting region when the concentration of Eu3+ions is small.更多还原