【作者】 侯涛；

【导师】 何大伟；

【作者基本信息】 北京交通大学 ， 光学， 2007， 硕士

【摘要】 VUV激发的稀土荧光粉是大屏幕壁挂式彩电PDP（等离子平板显示器）和无汞荧光灯应用技术的首先材料体系。硼铝酸盐对于稀土离子发光是一类很好的基质，其在VUV区有很强的吸收，发光效率较高，具有很好的耐真空紫外光辐照和抗离子轰击的能力。因此本文着重研究了稀土离子掺杂的硼铝酸盐荧光粉的合成及发光性能。本文采用高温固相法制备了稀土离子掺杂的MAl₂B₂O₇:Re(M=Ca，Sr，Ba；Re=Eu³⁺，Tb³⁺，Eu²⁺)系列荧光粉，并对其结构特性及发光性能进行了研究。样品的X射线粉末衍射数据与JCPDS标准卡片符合得很好，激活离子的掺入只是取代了碱土离子晶格位置，并没有引起基质结构的明显变化，表明我们合成了需要的材料。在MAl₂B₂O₇:Eu³⁺（M=Ca，Sr，Ba）系列样品，分别测定了该荧光体激发光谱和发射光谱，我们发现该材料在真空紫外区域有很强的吸收。样品的激发谱在130-170nm和230nm区域有两个很强的宽的吸收带，位于130-170nm的吸收带主要是硼氧和铝氧集团的吸收；位于230nm附近的吸收主要是Eu³⁺电荷转移态的吸收。随着Ba和Ca取代Sr，基质吸收强度明显降低，并且向低能方向移动了，基质吸收由峰值位于167nm附近的谱带，向峰值位于172nm附近的谱带移动了大约5nm左右，而230nm左右的稀土离子的吸收是明显增加的。当样品在172nm激发下，CaAl₂B₂O₇:Eu³⁺的真空紫外激发（172nm）的发光谱，发射光谱主要由峰值位于592nm，613nm，627nm的三个峰组成，其中592nm左右的发射最强：对应于Eu³⁺的⁵D₀→⁷F₁跃迁发射，为磁偶极跃迁；由于MAl₂B₂O₇:Eu³⁺（M=Sr，Ba）中Eu³⁺占据更多的是非对称格位，以⁵D₀→⁷F₂跃迁为主，对应613nm处的发射强度最大。在MAl₂B₂O₇:Tb³⁺（M=Ca，Sr，Ba）系列样品中，样品的VUV激发谱在120～200nm和200～300nm光谱区有两个较强的吸收带。位于120～200nm内的激发带主要是基质吸收，基质晶格中稀土离子被硼酸根离子分隔开，这包括硼氧和铝氧基团在真空紫外的吸收。Tb³⁺的（4f⁸→4f⁷5d）吸收位于200～300nm的区域内，并观察到基质与稀土离子Tb³⁺之间存在较强的能量传递。从发射光谱可以发现，在172nm的激发下，发射峰由492 nm，546 nm，592 nm和624 nm组成，分别对应Tb³⁺的⁵D₄→⁷F_J（J=6，5，4，3）跃迁发射，其中546 nm是主发峰。当材料中掺杂Ce³⁺时，材料在VUV的吸收降低，而在紫外增强，主要是Ce³⁺降低了基质和Tb³⁺在真空紫外区的吸收，Tb³⁺的发光有明显的猝灭现象，因为Ce³⁺离子的自我捕获激子的能力是很强的，Ce³⁺、Tb³⁺离子形成一种竞争吸收真空紫外光子的现象，然而他们之间的能量传递效率是要小于1的，所以共掺稀土离子的样品中，发光效率是要小于单掺稀土离子的样品的。因此在PDP荧光粉材料中尽量避免Ce³⁺的存在。在样品BaAl₂B₂O₇:Eu²⁺在真空紫外有很好的吸收，在172nm激发下可以发出434nm的蓝光。不同掺杂浓度离子Ba_1-XSr_XAl₂B₂O₇:Eu²⁺在172nm激发下，我们可以看出随着Sr²⁺浓度的增加，这是由于Sr²⁺比Ba²⁺的半径小，电荷密度就大，接受配体电子的能力弱。样品的发射强度不断减弱，并且峰值向长波方向移动。更多还原

【Abstract】 In recent years, more attention has been paid to PDP （Plasma display panel ）because of its potential market in the illumination. Special attention has been paid to the development of new and efficient VUV-excited phosphors. On the other hand, borates are of interest as host lattices for luminescent ions, because of their large band gap. Based on this consideration, it is valuable to investigate the alkaline borate family. In this paper, The VUV excitation and luminescence characteristics of MAl₂B₂O₇:Re(M = Sr, Ba, Ca; Re= Eu³⁺,Tb³⁺, Eu²⁺) have been studied.In this work, a series of powder samples of MAl₂B₂O₇:Re(M=Ca, Sr, Ba; Re= Eu³⁺,Tb³⁺, Eu²⁺)was prepared under a reducing atmosphere by solid-state reaction.. The X-ray powder diffraction data of MAl₂B₂O₇:Re are in agreement of JCPDS standard card which indicates that single-phased phosphor can be obtained in such synthesis process.The excitation spectrum of MAl₂B₂O₇: Eu³⁺ （M=Sr, Ba, Ca） are composed of two broad bands. One band in the range from 130 nm to 170 nm is attributed to the borate groups, and the other band at 230 nm is due to the charge-transfer state （CTS） of the Eu³⁺ ion. The excitation peak shifts from 167nm to 172nm when the Sr²⁺ ions are completely replaced by the Ba²⁺ and Ca²⁺ ions. It is obvious that the wavelength positions of the excitation bands depend much more on hosts. The lattice parameters of the phosphors increase and the crystal-field strength decrease with increasing of the ionic radius of Ca²⁺, Sr²⁺ and Ba²⁺.Because Eu³⁺ ions doped into CaAl₂B₂O₇ occupy centrosymmetric site, the emission of magnetic dipole transition 5D₀→7F₁ is stronger than electric dipole transition. As Eu³⁺ ions doped into MAl₂B₂O₇ （M=Sr, Ba） occupy Ba²⁺ or Sr²⁺ sites which is non-centrosymmetric site, so that the emission of electric dipole transition ⁵D₀→⁷F₂ is stronger than magnetic dipole transition in those series sample. The strong emission line at 613 nm is due to the hypersensitive electric dipole transition of ⁵D₀→⁷F₂. The weaker emission around 592 nm is due to the magnetic dipole transition ⁵D₀→⁷F₁.As for MAl₂B₂O₇:Tb³⁺ （M=Sr, Ba, Ca） the VUV excited spectra consists of one broad band in the range from 120 nm to 170 nm and the band peaking around 226 nm, and 270 nm respectively. The band （130～170nm） is also assigned to absorption of the borate groups. The bands which cover the spectral range from 160 to 270nm are due to the transitions of Tb³⁺（4f⁸→4f⁷5d ）.When Ce³⁺ is doped into the samples, the absorption band of samples obviously decreased in VUV. In PL spectra of MAl₂B₂O₇:Tb³⁺ （M=Sr, Ba, Ca）, there are four peaks at 487 nm, 546 nm, 589 nm and 619 nm corresponding to ⁵D₄ →⁷F_J （J=6,5,4,3） transition of Tb³⁺ respectively. Among these transitions, the green emission around 545 nm （⁵D₄→⁷F₅） is the strongest because it is a magnetic dipole allowed transition with △J=±1The excitation spectrum of BaAl₂B₂O₇: Eu²⁺show a high absorption band which obviously decreased in VUV. The emission spectrum of Ba_1-xSr_xA₁₂B₂O₇:Eu²⁺move to longer wavelength with increasing of Sr²⁺ mole concentration.更多还原