【作者】 开卫芳；

【导师】 黄彦林；

【作者基本信息】 苏州大学 ， 材料学， 2010， 硕士

【摘要】 稀土离子掺杂的发光材料在发光器件、激光和探测等多种领域得到广泛应用。Sm²⁺掺杂的发光材料可以实现永久光谱烧孔,对高密度光存储具有潜在的的应用。在照明和显示领域Eu³⁺是应用最多的红发光激活离子。Sm²⁺和Eu³⁺还是很好的结构探针离子,在晶格之中的周围环境对于其发光光谱和衰减影响很大。利用这个特点,可以研究Sm²⁺和Eu³⁺离子所处的周围结晶学环境,提供了基质中不同发光中心格位的对称性,进而给出物质结构的详细信息。本论文选择了正磷酸盐作为基质材料,以Sm³⁺和Eu³⁺作为激活离子,用高温固相反应法分别制备了Sm³⁺和Eu³⁺离子掺杂的磷锶钡钠石(NaSr_1-xBa_xPO₄)、并用X射线辐照法实现了Sm²⁺离子在磷锶钡钠石和KSrPO₄中的还原,研究了Sm²⁺和Eu³⁺离子的发光性能,讨论了缺陷和发光性能的内在关联。第三章探讨了不同的锶、钡比对NaSr_1-xBa_xPO₄晶体结构、Sm²⁺还原效率及其发光性能的影响;通过对荧光光谱的分析,研究了NaSr_1-xBa_xPO₄样品中稀土离子的晶体学环境。结果表明:随着Ba含量的增加,NaSr_1-xBa_xPO₄的晶胞参数和单胞体积逐渐增大,并且伴随着XRD衍射峰向低角度的迁移;随着Ba含量的增加,NaSr_1-xBa_xPO₄中Sm²⁺离子的还原效率增强,而相应的5D0→7F0发光跃迁的衰减时间减小;Sm²⁺在NaSr_1-xBa_xPO₄中的结构具有一个强烈扰动的晶体场环境,主要是由Sr（Ba）在晶格中的占位混乱和晶格中由X射线辐照产生的复杂缺陷造成的。第四章探讨了Sm²⁺离子掺杂KSrPO₄的发光光谱、Sm²⁺离子的晶体学位置和温度对荧光特性的影响。研究表明:Sm²⁺在KSrPO₄的晶格中占据三种不同晶体学结构的阳离子位置。Sm²⁺离子的发光光谱有一组线状的发光谱线（688-715 nm）与位于650–800 nm处的宽带发射组成,线状光谱来自Sm²⁺离子的5D0→7FJ （J=0, 1, 2）跃迁,宽带发射则归因于Sm²⁺离子的5d→4f辐射跃迁。Sm²⁺离子5D0→7F0的宽带发射跃迁同时也表明Sm²⁺掺杂的KSrPO₄结构具有一个强烈扰动的晶体场环境,主要是由Sr/?K位置占位混乱和基质中Sm²⁺离子在Sr/?K位置上的复杂取代作用造成的。该结论对于其他稀土离子在KSrPO₄中的发光和应用研究具有参考意义。例如,Sm²⁺和Eu²⁺离子半径和化学性质近似,可以由此推测出KSrPO₄中Eu²⁺的结晶学位置和发光光谱特点。第五章,用X射线衍射（XRD）、傅里叶变换红外光谱（FT-IR）、傅里叶变换拉曼光谱（FT-Raman）和扫描电镜（SEM）等技术对Eu³⁺掺杂的NaSr_1-xBa_xPO₄物相组成、结构和晶体形貌进行了表征。探讨了不同晶体结构中Sr/Ba比对晶体结构,发光性能和发光寿命的影响。实验通过对Eu³⁺的发光特点的表征和研究,分别测试了Eu³⁺离子的室温激发光谱和发射光谱。研究表明:NaSr_1-xBa_xPO₄属简单六方晶系,所有的振动均来自PO₄3?阴离子基团;Eu³⁺占据非反演中心的格位,该材料中阳离子位置具有高度扰动性的特点;Eu³⁺离子的发光衰减是单指数衰减曲线。随着晶体结构之中钡含量的增加,Eu³⁺离子5D0→7F2与5D0→7F1的发光强度之比明显增大,说明Eu³⁺离子在晶格中的对称性明显降低。该高比值,对掺杂材料的发光强度和发光的色度都是有益的。本论文创新点是在NaSr_1-xBa_xPO₄中成功实现了Sm²⁺在X射线辐照下的还原,并首次报道了稀土掺杂的NaSr_1-xBa_xPO₄的微结构、X射线辐照时间和钡含量对Sm²⁺还原效率的影响;Sm²⁺离子掺杂的KSrPO₄结构特点,Sm²⁺离子的晶体学位置和温度对样品荧光性的影响。这些对于NaSr_1-xBa_xPO₄和KSrPO₄的进一步应用、稀土离子的还原方法的发展都具有参考借鉴和实际应用价值。更多还原

【Abstract】 Rare-earth doped light-emitting material has been paid intense attention because it has been widely used in various fields, such as in display devices, laser and display. Sm²⁺ ion has potential application in high-density optical storage because of its property of persistent spectral hole burning. Eu³⁺ as activating ions has been the most widely used in the field of luminescence and display. Sm²⁺ and Eu³⁺ ions are also two good kinds of probe material. It highly affected on the spectra and decay. Take advantage of this feature, we can study the surrounding environment of Sm²⁺ and Eu³⁺ ions which provides the symmetry of different luminescence centers in the matrix and then gives details of physical structures.This paper chose the orthophosphate as a substrate material, Sm³⁺ and Eu³⁺ as activating ions, Sm³⁺ and Eu³⁺ ions doped strontium barium phosphate sodalite (NaSr_1-xBa_xPO₄). Sm²⁺ ion was reduced by X-ray irradiation in strontium barium phosphate sodalite and KSrPO₄. We studied the luminescence of Sm²⁺ and Eu³⁺ ions and discussed the relationgship between defect and luminescence.In the chapter three, the effect of different mole ratios of Sr/Ba on the crystal structure, the reduction of Sm²⁺ and the luminescence of Sm²⁺ in NaSr_1-xBa_xPO₄ were also discussed; we studied the crystal field environment of RE ions in NaSr_1-xBa_xPO₄ through the analysis of the fluorescence spectra. The results show that with increasing of Ba atoms the crystallography parameters and the volume of cell in NaSr_1-xBa_xPO₄ is increased and the main XRD peaks shift to low degree, the reductive efficiencies of Sm²⁺ ions in NaSr_1-xBa_xPO₄ are enhanced, while the corresponding decay time of 5D0→7F0 transition decreases rapidly. The structure of Sm²⁺ in NaSr_1-xBa_xPO₄ is a heavily disturbed crystalline environment due to the Sr（Ba） disorder and the complicated defects in the lattice created by the X-ray irradiation.In the chapter four, we discussed the fluorescence spectra of Sm²⁺-doped KSrPO₄, crystallographic position of Sm²⁺ ions and the temperature effects on the fluorescence. It was found that there were three crystallographic cationic sites available for Sm²⁺. Fluorescence spectra of Sm²⁺ ions is made up of the emission lines （688-715 nm） and the broad emission bands of 650–800 nm. The emission lines came from the 5D0→7FJ （J=0,1,2） transitions of Sm²⁺ ions. The broad emission bands are referred to the 5d→4f transition of Sm²⁺ ions. The 5D0→7F0 transitions of Sm²⁺ ions are broad which proves the structure of Sm²⁺ doped KSrPO₄ is a heavily disturbed crystalline environment due to the Sr/K disorder and the complicated substitutions among K, Sr and Sm²⁺ ions. These results can be helpful for the luminescence and application of the other RE ions in KSrPO₄. Since the ionic radii and the chemical properties for Sm²⁺ and Eu²⁺ are nearly identical, one may expect the crystallographic position and luminescence of Eu²⁺ in KSrPO₄.In the chapter five, characteristics of Eu³⁺-doped NaSr_1-xBa_xPO₄ were investigated by the use of XRD, SEM, FTIR and FT-IRaman spectra. The effect of different mole ratios of Sr/Ba on the crystal structure was also discussed. The excitation and emission spectra of Eu³⁺-doped NaSr_1-xBa_xPO₄ were discussed. The results show that NaSr_1-xBa_xPO₄ belongs to hexagon system, all the vibrations were from PO₄3? anion unit, the Eu³⁺ ion in crystal was located in non-reversion center in the lattice, the crystallographic site of cation in the crystal is highly disturbed and disordered. The decay exhibit a single exponential curve indecated that there is only one Eu³⁺ luminescence center. With the barium content increasing, luminous intensity ratio of 5D0→7F2 and 5D0→7F1 of Eu³⁺ ion increased significantly which indicated that Eu³⁺ ions in the crystal lattice symmetry decresed significantly. The high ratio is useful to the luminous intensity and color of the doped material.The novelties of this desertation are the following: we successfully achieved the reduction of Sm²⁺ in the NaSr_1-xBa_xPO₄ by X-ray irradiation. The microstructure of the RE ions doped NaSr_1-xBa_xPO₄, X-ray irradiation time and the content of Ba effect on the reduction efficiency of Sm²⁺ were first reported. Besides this, we also discussed the structural features of Sm²⁺-doped KSrPO₄, crystallographic position of Sm²⁺ ions in KSrPO₄ and the temperature effects on the fluorescence. These results are helpful in further research of NaSr_1-xBa_xPO₄ and KSrPO₄. And this also are good references for the reduction of rare-earth ions.更多还原