【作者】 焦芳芳；

【导师】 翟永清；

【作者基本信息】 河北大学 ， 应用化学， 2009， 硕士

【摘要】 硅酸盐体系发光材料由于其化学稳定性好,耐水性强,发光颜色多样,应用广泛等特点,越来越引起人们的重视。这类材料多采用传统的高温固相法制备,该法具有烧结温度高,反应时间长,产物晶粒大,硬度高等诸多缺点。凝胶-燃烧法是结合溶胶-凝胶法离子分散均匀和燃烧法快速高效的优点而开发出来的一种新型软化学方法。与传统的高温固相法相比,该法具有离子分散均匀,合成温度低,操作简单,晶粒度小,易研磨等优点。为节省能源,降低能耗提供了一种新的思路。本论文采用凝胶-燃烧法成功合成了一系列稀土离子掺杂的碱土多硅酸盐发光材料。借助XRD、SEM、荧光光谱等现代测试手段,对合成产物进行了分析和表征,得出以下结论：1.采用凝胶-燃烧法成功合成了高亮度蓝紫色发光材料CaMgSi2O6:Eu2+,属单斜晶系。焙烧温度为1000℃时,样品一次颗粒尺寸约300nm,基本成球形,随温度升高,颗粒有所增大。光谱分析表明：此发光体在450nm处有一个宽的发射峰,是由Eu2+的4f65d1-4f7跃迁所导致的,Eu2+在CaMgSi2O6:Eu2+中形成六配位的发光中心。此外,探讨了Eu2+的掺杂浓度和还原温度对材料发光亮度的影响。2.采用凝胶-燃烧法成功合成了一种新型碱土多硅酸盐基质SrMgSi2O6,并系统研究了Eu2+、Ln3+(Ln=La、Ce、Nd、Sm、Gd、Dy)共掺杂对材料物相结构、发光性质的影响。结果发现：SrMgSi2O6:Eu2+,Ln3+的晶体结构均为镁黄长石结构,属简单四方晶系；发射光谱的峰形、峰位基本一致,均为宽带连续谱,最大发射峰位于470nm附近,是典型的Eu2+的4f65d1→4f7跃迁引起的。系列材料均有蓝色长余辉发光现象。Ln3+为辅助激活剂,其种类对材料的发光强度和余辉性质有着重要的影响,余辉亮度由强到弱的顺序大致为：Dy3+>Nd3+>Eu2+>La3+>Gd3+>Ce3+>Sm3+;以Dy3+为辅助激活剂时余辉持续时间最长,约4h。此外,还探讨了Eu2+和Dy3+的掺杂浓度,还原温度以及H3BO3用量等对样品发光强度的影响,并用“位型坐标模型”对长余辉发光机理做出合理解释。3.采用凝胶-燃烧法成功合成了一种新型黄色发光材料SrMgSi2O6:Tb3+,属四方晶系。焙烧温度为1100℃时,样品一次颗粒近似球形,平均粒径约240nm。发射光谱主要由473nm、491nm、547nm、585nm等一系列窄带发射峰组成,分别归属于Tb3+从5D3→7F3,5D4→7F6,5D4→7F5和5D4→7F4的跃迁发射,547nm、491nm、473nm处的发射峰均较强,在紫外光照射下样品发黄光。此外发现,Tb3+的掺杂浓度及还原温度对材料发光性质有重要影响。4.采用凝胶-燃烧法成功合成了蓝色长余辉发光材料Sr3MgSi2O8:Eu2+,Dy3+,属正交晶系结构。发射光谱为—宽带谱,峰值位于460nm处,归属于Eu2+的4f65d1→4f7跃迁。激发光谱也为一宽带,主激发峰位于414nm,次激发峰位于400nm处,与高温固相法制得的Sr3MgSi2O8:Eu2+,Dy3+激发峰相比,出现了明显的红移现象。此外,探讨了还原温度、还原时间、H3BO3用量、尿素用量等对样品发光强度的影响。5.采用凝胶-燃烧法合成了系列新型红色多硅酸盐发光材料Sr2MgSi2O7:Eu3+和Sr3MgSi2O8:Eu3+。研究发现：少量Eu3+的掺杂对材料的晶体结构影响较小。系列样品的激发光谱在220-350nm之间均出现一宽带吸收,归属于O2-→Eu3+之间的电荷迁移带；350nm以后的锐线峰为Eu3+的f-f跃迁吸收峰,其最强锐线峰位于400nm。发射光谱由两强发射峰组成,分别位于592nm和618nm处,属于典型的Eu3+的5D0→7F1和5D0→7F2跃迁。此外,探讨了Eu3+浓度对材料发光强度的影响。在Sr2-xMgSi2O7:Eu3+x系列样品中,未发现明显的浓度猝灭,且材料发光强度较大；在Sr3-xMgSi2O8:Eu3+x系列样品中,当Eu3+摩尔浓度达到8%时,出现浓度猝灭现象。更多还原

【Abstract】 In the recent years, silicates phosphors are attracted more and more attention because of its good chemical stability, strong water resistance, light-emitting color variety and extensive applications.At present, the traditional method to synthesize silicate-host luminescence materials is solid-state reaction. But this process has a lot of disadvantages, such as the synthesis temperature is high, the reaction time is long, the partical size is large, and the hardness of the powder is strong, it need grounding to reduce the particle size, which results in the decrease of luminescent brightness and afterglow. So this method is restricted for further development. Therefore, exploring new synthesis method is gradually eyed by more and more people.Gel-combustion method is a new soft-chemical process combined with ion homogeneous distribution of sol-gel method and high efficiency of combustion method. Compared with traditional solid state reaction, gel-combustion method has many advantages, such as uniform composition, short calcination time, simple operation, and small particles, and so on. It provides a new idea for saving energy and lowering energy consumption.In our pesent work, a series of alkaline earth polysilicate phosphors doped with rare earth ions were successfully synthesized by gel-combustion method. The as-synthesized phosphors were investigated by X-ray diffraction analysis (XRD), scanning electron microscope (SEM) and Fluorescence spectrophotometer. According to that, we get some valuable conclusions as follows:1. Blue-purple emitting material CaMgSi2O6:Eu2+ with high brightness was synthesized by gel-combustion method in weak reductive environment. The as-synthesized CaMgSi2O6:Eu2+ has monoclinic crystal structure. When the calcination temperature is 1000℃, the initial particles are nearly spherical in shape, and the mean size is about 300nm. The particle size increases with the increase of the calcination temperature. Spectral analysis indicates that this phosphor has a broad band emission peak at 450 nm, this peak was made by the transition 4f65d1→4f7 of Eu2+, which was caused by the [EuO6] emitting center formed in CaMgSi2O6 host. Moreover, the effects of different concentration of doped Eu2+ and reductive temperature on the luminescent property were investigated.2. On the basis of the synthesis of a novel host SrMgSi2O6 by gel-combustion method, the effects of co-doped Eu2+ and Ln3+(Ln=La, Ce, Nd, Sm, Gd, Dy) on the crystal structure and luminescent properties were investigated in detial. It is found that SrMgSi2O6:Eu2+,Ln3+ phosphors have akermanite structure and belong to tetragonal crystal structure. The shape and position of peaks in emission spectrums have almost no change with the variation of co-doped Ln3+. The emission spectrums are all broad band continuous spectrums and the main peak is at 470nm. The series of samples show long afterglow properties. But the kind of doped auxiliary activators has great effects on the luminescent intensity and the long afterglow properties of the materials. The approximate order of long afterglow intensity are as folows:Dy3+> Nd3+> Eu2+> La3+> Gd3+> Ce3+> Sm3+. Among them, Dy3+ is best on. The persistence time of Sr0.94MgSi2O6:Eu2+0.02, Dy3+0.04 is the longest, about 4h. Moreover, the effects of the concentration of Eu2+ and Dy3+, the reductive temperature and the dosage of H3BO3 on luminescent intensity were discussed. Also, the long afterglow luminescence mechanism of SrMgSi2O6:Eu2+,Ln3+ was explained.3. A novel yellow emitting material SrMgSi2O6:Tb3+ was synthesized by gel-combustion method in weak reductive environment. The as-synthesized SrMgSi2O6:Tb3+ phosphors possess the similar tetragonal crystal structure. When the calcination temperature is 1100℃, the initial particles are nearly spherical in shape, and the mean size is about 240nm.The emission spectrum is composed of a series of sharp peaks, located respectively at 473nm, 491nm,547nm,585nm. These emission peaks are ascribed respectively to Tb3+ ions transition of 5D3→7F3,5D4→7F6,5D4→7F5,5D4→7F5 in SrMgSi2O6 host. The emission peak at 547nm,491nm and 473nm are all strong, the samples show yellow emitting under UV irradiation. Moreover, it is found that the concentration of doped Tb3+ and reductive temperature have great significant effect on the luminescent property of the phosphors.4. The persistent phosphor Sr3MgSi2O8:Eu2+,Dy3+ with orthorhombic system was successfully synthesized by gel-combustion method. Its emission spectrum is a broad band with the peak at about 460nm due to the typical transition of 4f65d1→4f7 from Eu2+; the excitation spectrum is also a broad band with a main peak at about 414nm and the secondary at about 400nm. Compared with Sr2.94MgSi2O8:Eu2+0.02,Dy3+0.04 synthesized by high temperature solid-state reaction, excitation spectrumof as-synthesized sample shift to long wavelength. Moreover, the effects of reductive temperature, reductive time, the mol fraction of H3BO3 and the dosage of urea on the luminescent property were investigated.5. A series of new red-emitting polysilicate phosphors Sr2MgSi2O7:Eu3+ and Sr3MgSi2O8:Eu3+ were successfully synthesized by gel-combustion method. It is found that doped Eu3+ has little effect the structure of the host. The excitation spectra of the samples show a broad band between 220nm and 350nm, which is ascribed to the charge transference from O2- to Eu3+. The sharp peaks after 350nm are due to the f-f transition from Eu3+, of which the strongest one is located at 400nm. The excitation spectrum is composed of two strong emission peaks located at 592nm and 618nm respectively, which are attributed to the transition 5D0→7F1 and 5D0→7F2 of Eu3+ respectively. Besides, the effects of different concentration of doped Eu3+ on the luminescent intensity were investigated. It is interesting that the concentration quenching can not be found in the samples of Sr2-xMgSi2O7:Eu3+x, and their red-emitting is very bright. Among the samples of Sr3-xMgSi2O8:Eu3+x, the concentration quenching occurs when the concentration of Eu3+ is 8%.更多还原