【作者】 邱子凤；

【导师】 吕孟凯；

【作者基本信息】 山东大学 ， 材料学， 2009， 博士

【摘要】 纳米发光材料明显不同于体相发光材料的特性已经成为近年来的热点研究课题。含铝、锆复合氧化物具有良好的化学稳定性和热稳定性,是一类重要的光活性基质材料。目前,制备含铝、锆复合氧化物的主要方法还是传统的高温固相反应法,采用湿化学法制备的报道并不多。因此,在本论文中,我们采用溶胶-凝胶燃烧法制备了不同激活离子掺杂的含铝、锆复合氧化物纳米发光材料,并系统地研究了其发光特性,观察到了一些新的发光现象。另外,还制备了稀土掺杂的介孔SrAl₂O₄和CaAl₂O₄纳米颗粒,并进行了表征。在第一章中,我们对发光理论、稀土发光材料的发光机理、制备方法、表征手段及稀土纳米发光材料的性能特点等作了简单的介绍,并对含铝、锆复合氧化物发光材料的研究现状进行了总结。在第二章中,我们首次采用溶胶-凝胶燃烧法制备了CaAl₂O₄,BaAl₂O₄和SrAl₂O₄基纳米晶长余辉发光材料,并在其中引入了稀土激活离子Ln³⁺（Ln=Eu、Dy、Nd、La）,系统地研究了它们的光致发光性质及基质对稀土离子发光的影响。结果显示,600℃低炉温燃烧6 min便可制备较纯的CaAl₂O₄,BaAl₂O₄和SrAl₂O₄纳米晶,分别为正交晶系,六方晶系和单斜晶系,共掺的稀土激活离子并未改变晶体结构。SrAl₂O₄:Eu²⁺,D³⁺,BaAl₂O₄:Eu²⁺,Nd³⁺和CaAl₂O₄:Eu²⁺,La³⁺的发射光谱峰值分别为516 nm,500 nm和440 nm,对应发射光的颜色为黄-绿,蓝-绿和蓝-紫,相同的发光中心受晶体场的影响导致发射波长不同。我们认为,材料表现出长余辉特性的根源在于晶体中陷阱能级的存在。不同的共掺离子为Eu²⁺在不同的晶体结构中创造合适的陷阱能级,其余辉时间和陷阱能级中储存的能量和电子数量有关;而余辉强度与电子从陷阱能级逃离的速度和能量传递的速度有关。实验中我们所得产物的余辉时间约为7 h,要略短于用固相烧结法所得产物的余辉时间。我们在没有任何模板或有机添加剂辅助的情况下,利用超声-燃烧法成功地制备出具有介孔结构的CaAl₂O₄:Eu²⁺,La³⁺长余辉纳米发光颗粒,并对其进行了表征。N₂吸附-脱附等温曲线中有一明显的滞后环,这足以证明其介孔结构。介孔CaAl₂O₄:Eu²⁺,La³⁺纳米颗粒的比表面积为20.30 m²/g。孔的形成,是由于在超声过程中形成均匀胶粒并堆积,而在燃烧过程中失去水分所致。同样地,在没有任何模板或有机添加剂辅助的情况下,首次利用超声-燃烧法和回流-燃烧法成功地制备出具有介孔结构的SrAl₂O₄:Eu²⁺,La³⁺长余辉纳米发光颗粒,并对回流-燃烧法所得产物进行了表征。其比表面积为13.45 m²/g。孔的形成也是由于在回流过程中,堆积的胶粒间隙在燃烧过程中失去水分所致。在第三章中,我们首次采用柠檬酸盐溶胶-凝胶燃烧法制备了强红光发射荧光材料Li_0.9Y_{（0.9-x-y）}Zr_0.1O₂:Eu_x³⁺,R_y³⁺（R=Ce,Bi,Dy）。其中Li_0.9Y_{（0.9-x-y）}Zr_0.1O₂:Eu_x³⁺,D_y³⁺（x=0.02,y=0.016）的红光发射强度与日本商用粉Y₂O₂S:Eu³⁺（Kasei OptonixLtd.,Japan）基本相同,且当掺杂离子浓度较高时,试样表现为全色发射。燃烧炉温为800℃,远远低于固相烧结法的1200℃。由XRD的结果决定前驱体溶液中须加入过量10mol%的Li,因为随着燃烧温度的增加,Li的挥发量也增加。室温下,产物表现出高显色指数的红光发射（激发波长395 nm）。周围低的对称性使得Eu³⁺的电子跃迁辐射的能级简并度部分解除,提高发光强度,增强发光峰的劈裂程度,同时出现⁵D₀→⁷F_1,2,3,4跃迁发射峰,其中三个⁵D₀→⁷F₁发射峰,两个⁵D₀→⁷F₂发射峰。Ce和Bi作为敏化剂被分别加入到体系中,使得Eu³⁺的发光强度得到了很大提高,从发光测试的结果看分别提高了900%和600%。说明敏化剂和发光中心之间的能量传递是有效的。Li_0.9Y₍（0.9-x-y）Zr_0.1O₂:Eu_x³⁺,Dy³⁺的发射光谱峰值仍位于613nm处,且当Eu和Dy的浓度增加到一定程度后,Eu³⁺的发光强度降低,但同时在蓝光和绿光区域分别出现了发射峰,我们将其归因于产物中Dy³⁺的⁴F_9/2→⁶H_13/2和Eu²⁺跃迁辐射。荧光显微镜照片显示,呈现全光发射。我们采用柠檬酸盐溶胶-凝胶燃烧法和后续热处理两步合成法制备了Ba₂YZrO_5.5和Ba₂YZrO_5.5:Eu纳米晶,并对其结构和发光性质进行了研究。结果显示,800℃燃烧后,产物结晶性能不好,1100℃热处理1 h后,产物结晶性变好。Ba₂YZrO_5.5属立方钙钛矿结构,其晶胞为理想钙钛矿结构的两倍。其发光峰位于468 nm,514 nm和637 nm,分别属于晶体的[ZrO₅-V（o|¨）-YO₆]基团的金属-配体电荷转移态跃迁,氧空位之间的电子跃迁和晶体表面态缺陷发光。Ba₂YZrO_5.5:Eu表现出典型的Eu³⁺的发光,发射峰位于615nm,属⁵D₀→⁷F₂跃迁。我们首次采用800℃柠檬酸盐溶胶-凝胶燃烧法制备了白光发射荧光材料Ba₂LaZrO₆:Ce,并对其结构和发光性质进行了研究。与Ba₂YZrO_5.5一样,属立方钙钛矿结构,其晶胞为理想钙钛矿结构的两倍。室温下,发射峰位于467 nm,535 nm和623 nm处。其中蓝光发射属于晶体的[ZrO₅-V（o|¨）-LaO₆]基团的金属-配体电荷转移态跃迁,535 nm处的发光对应Ce³⁺的5d-4f跃迁,而红光发射是Ce³⁺发射发生红移的结果。产物的CIE坐标为（0.298,0.317）,可以看出其发射光位于白光区域。在第四章中,我们对本论文的工作进行了总结。更多还原

【Abstract】 Nanoscaled luminescent materials have been the hot research because of their peculiar characteristics compared to bulk counterparts.Alkaline earth aluminates and zirconates have excellent thermal and chemical stability.They are an important kind of photoactived host materials.At present,solid state reaction method has been used to prepare alkaline earth aluminates and zirconates,while wet chemistry method is less reported.In this dissertation,alkaline earth aluminates and zirconates luminescent nanomaterials prepared by citrate sol-gel combustion method have been reported,and their photoluminescent properties were investigated systemically,some new luminescent phenomena were detected.In addition,mesoporous rare-earth（RE） ions-doped BaAl₂O₄ and CaAl₂O₄ nanoparticles were prepared and characterized.In Chapter 1,we briefly introduced the theory of luminescence,the luminescent mechanism,preparation methods,characterization means and properties of lanthanide luminescent materials.The research progress in the field of alkaline earth aluminates and zirconates luminescenct materials was also summarized.In Chapter 2,Eu²⁺,R³⁺ co-doped alkaline earth aluminates MAl₂O₄:Eu²⁺,R³⁺（M = Sr,Ba and Ca;R = Dy,Nd and La） nanoparticles with high brightness and long afterglow have been prepared by solution-combustion synthesis at 600℃without a post-annealing process for the first time.We studied luminescent properties of the samples and influence of host on luminescent properties.The samples crystallized in monoclinic phase structure of SrAl₂O₄,the hexagonal phase structure of BaAl₂O₄ and the orthorhombic phase structure of CaAl₂O₄ respectively.The little amount of doped rare earth ions has nearly no effect on the phase structures.It’s observed that from SrAl₂O₄:Eu²⁺,Dy³⁺ to BaAl₂O₄:Eu²⁺,Nd³⁺ and to CaAl₂O₄:Eu²⁺,La³⁺,the main peaks of emission spectra of the luminescent nanoparticles shift to shorter wavelength（from 516nm to 500nm and then to 440nm）,and correspondingly,the luminescence changes from yellow-green to blue-green and then to blue-purple.This phenomenon is derived from the changing of the matrix crystal structure.The existence of trap level should answer for the properties of long-persistent luminescence.The appropriate trap level in different host was formed by different co-dopant ions for Eu²⁺.The lifetime of afterglow is related with the energy store in the trap level and the number of electrons which stay in the trap level.The intensity of afterglow is related with the velocity,including the velocity of electrons escape from the trap level and the velocity of energy transfer.The afterglow of phosphor nanoparticles,which allowed the time to be visually recognized （≥0.32mcd/m²）,lasted for over 7h after the excited source was cut off.In fact,the afterglow time of the samples is shorter than that of the powders prepared by the solid-state reaction method.Mesoporous CaAl₂O₄:Eu²⁺,La³⁺ long lifetime luminescence nanoparticles have been successfully prepared without using any templates or surfactants by sonication-combustion synthesis.The porous structure was confirmed by the hysteresis loop in the N₂ adsorption-desorption isotherm.The Brunauer-Emmett-Teller（BET） surface area is 20.30m²/g.The uniform sol-granules were formed in the sonication progress and the accumulating of nanometer sized sol-granules created a network.The channels were filled with water.The pore formation is attributed to the loss of water molecules during the combustion process.Mesoporous SrAl₂O₄:Eu²⁺,Dy³⁺ long lifetime luminescence nanoparticles have been successfully prepared without using any templates or surfactants by sonication-combustion and refiuxing-combustion synthesises.The Brunauer-Emmett-Teller（BET） surface area is 13.45m²/g.The mechanism of mesoporous SrAl₂O₄:Eu²⁺,Dy³⁺ made by sonication-combustion and refiuxing-combustion synthesises is similar to the one of CaAl₂O₄:Eu²⁺,La³⁺.In Chapter 3,we studied the preparation and luminescent properties of Li_0.9Y_{（0.9-x-y）}Zr_0.1O₂:Eu_x³⁺,Ry³⁺（R=Ce,Bi,Dy） nanocrystals.Low temperature citrate sol-gel combustion method has been used to prepare the samples,and the combustion method has been confirmed to be an efficient method of preparing zirconates nanocrystals.A considerable loss of the lithium is induced at high temperature due to the evaporation,the amount of lithium loss being proportion to the firing temperature. So,amount of excess Li component was needed to obtain the composition close to the nominal one.In our experiments,the precursors contained excess 10 mol%amount of Li according to the stoichiometric amount.It can be seen that combustion the metal urea-citrate precursor at 800℃is sufficient for the formation of pure crystal phase from the data of XRD.Nevertheless,such a low reaction temperature is surprising because the product was formed at 1200℃when employed solid-state reaction. Li_0.9Y_（0.9-x）Zr_0.1O₂:Eu_x³⁺ nanopowders exhibit a strong red emission under 395 nm excited.The lower symmetry of the Eu³⁺ sites can increase the emission intensity and the extent of peak splitting of Eu³⁺.The emissions of Li_0.9Y_（0.9-x）Zr_0.1O₂:Eu_x³⁺ from the ⁵D₀→⁷F_1,2,3,4 transitions of the Eu³⁺ ions were detected,including three ⁵D₀→⁷F₁ transitions and two ⁵D₀→⁷F₂ transitions.Ce and Bi were introduced into the system as co-activator as well as sensitizer of luminescence and the luminescence intensity of Li_0.9Y_{（0.9-x-y）}Zr_0.1O₂:Eu_x³⁺ were increased in 900%and 600%respectively.This observation unequivocally shows that the energy transfer from Bi³⁺ to Eu³⁺ is very efficient.Photoluminescence spectra of Li_0.9Y_{（0.9-x-y）}Zr_0.1O₂:Eu_x³⁺,Dy_y³⁺ samples indicated the dominant red emissions（613nm） at a single-wavelength ultraviolet excitation（395nm） due to ⁵D₀→⁷F₂ transition.When the concentration of Eu³⁺ and Dy³⁺ exceeded a critical amount（5mol%and 4mol%respectively）,the red emission became lower coincidence with the appearance of blue and green emission which attribution to ⁴F_9/2→⁶H_13/2 transition of Dy³⁺ and Eu²⁺ transition.Pure and Eu-doped Ba₂YZrO_5.5 nanoparticles have been prepared by sol-gel combustion method and post-annealing process in this work.Photoluminescence properties and structure character were studied clearly.From XRD datas we could see that the samples have lower crystallinity after the combustion process at 800℃;and post-annealing process at 1100℃was necessary.The samples have the cubic perovskite structure with about double cell of ideal perovskite. Three emission bands centered at 468 nm,514 nm and 637 nm can be detected,and were ascribed to the metal-to-ligand charge-transfer transition（MLCT） in [ZrO₅-V（o|¨）-YO₆]groups,electrons transition between oxygen vacancies and the emission from surface state defects,respectively.Ba₂YZrO_5.5:Eu indicated the dominant red emissions（615nm） at a single-wavelength ultraviolet excitation（395nm） due to ⁵D₀→⁷F₂ transition.Ba₂LaZrO_5.5:Ce full-color-emitting phosphor has been prepared by sol-gel combustion method at 800℃.The structure character is similar to Ba₂YZrO_5.5. Three emission bands centered at 467 nm,535 nm and 623 nm can be detected,and were ascribed to the metal-to-ligand charge-transfer transition（MLCT） in [ZrO₅-V（o|¨）-LaO₆]groups,the 5d-4f transition of Ce³⁺ and the redshift of Ce³⁺ emission. The chromaticity coordinate of Ba₂LaZrO_5.5:Ce³⁺0.03 was（0.298,0.317）.In chapter 4,a concise summary of the contents was given.更多还原