【作者】 李艳琴；

【导师】 王育华；

【作者基本信息】 兰州大学 ， 材料物理与化学， 2011， 博士

【摘要】 长余辉发光材料因其环保节能备受人们关注,近年来,随着人们环保节能意识的加强以及国家节能减排战略的实施,为长余辉材料的发展营造了更加良好的市场氛围,同时也对长余辉材料的余辉性能及颜色提出更高的要求。目前,研究较多的主要是Eu2+激活的铝酸盐、硅酸盐等蓝色和绿色长余辉材料,但能够满足实际应用的只有绿色长余辉材料,严重缺乏性能较好的长波长长余辉材料。此外,虽然多种长余辉材料已被开发,部分已被应用,但长余辉发光机理尚未取得共识,无法为长余辉材料的开发和研究提供有力的理论指导。针对上述问题,本论文采用高温固相法主要合成了一系列Eu2+为激活剂的氧化物材料,系统研究了其发光特性,并探讨了它们的余辉性能或作为长余辉材料的可能性。本论文涉及的工作主要有以下几个方面：首先是对蓝色长余辉材料Sr2MgSi2O7:Eu2+,Dy3+进行了研究和改进。在对Sr2MgSi2O7:Eu2+,Dy3+的研究过程中,发现掺入第三种激活离子Ce3+后,Ce3+→Eu2+间存在能量传递,同时Ce3+具备电子陷阱的作用,因此掺杂Ce3+后,不仅提高了其初始亮度而且延长了余辉时间。此外,也考察了原料Si02的量对Sr2MgSi2O7:Eu2+,Dy3+结晶性、发光及其余辉性能的影响,研究发现适量的Si02过量可以显著改善样品的余辉性能。在新型长余辉材料的开发方面,系统地研究了Eu激活的CaMgSiO4, Eu激活的BaMgSiO4, Sr3Al2O5Cl2:Eu2+, R3+(R=Dy, Nd, Tm)和M2TiA2O8:Pr3+(M=Sr, Ba, A=Si,Ge)四种体系的发光特性。研究表明,BaMgSiO4:Eu2+和Sr3Al2O5Cl2:Eu2+,R3+ (R= Dy, Nd, Tm)分别为绿色长余辉材料和橙黄色长余辉材料,其余体系内没有发现长余辉现象。值得一提的是,在CaMgSiO4:Eu2+中Eu2+的发光几乎完全猝灭,文中利用能带模型成功地解释了该现象。本文的一个重要的工作是在绿色长余辉材料BaMgSiO4:Eu2+中观察到在紫外光激发下Eu2+离化为Eu3+,同时样品的颜色由浅绿色变为粉红色。但在空气气氛下制备的BaMgSiO4:Eu中没有观察到Eu2+离化为Eu3+及样品颜色的改变。文中详细地分析Eu2+离化为Eu3+的原因,并以此为依据,对现有的以Eu2+为激活剂的长余辉机理进行了修正。更多还原

【Abstract】 Long-lasting phosphorescence (LLP) materials have attracted considerable attention for various displays and signing applications as friendly environmental and energy economized materials. As the awareness of environmental protection and energy saving is increased, LLP material will have wider prospect of market. So the exploration of multiple color-emitting is promising and thus has attracted intensive research interests. Nowadays, a great amount of novel LLP materials based on different hosts have been reported in the literature. Only green LLP materials SrAl2O4:Eu2+, Dy3+ is commercially applied. Long wavelength emitting (>600 nm) materials with phosphorescence is in great scarcity. Therefore, there is a strong desire for the development of phosphors with long wavelength emissions in recent years. In addition, the phosphorescence mechanism in Eu2+containing phosphors has been the subject of many investigations. Up to now, countless reports have been published on the phosphorescence mechanisms of Eu2+-containing phosphors, but only a few mechanisms have outlived advances in experimental and theoretical methods. In this paper, a series of Eu2+ phosphors were synthesized by solid-state reaction and their luminescence properties were systematically investigated. In addition, the luminescence properties of M2TiA2O8:Pr3+(M=Sr, Ba, A=Si,Ge) were also studied with the aim of exploration of red LLP materials.In this paper, firstly, we try to improve the LLP properties of blue-luminescence Sr2MgSi2O7:Eu2+, Dy3+ by the addition of Ce3+. The triply doped phosphor Sr2MgSi2O7:Eu2+, Dy3+, Ce3+ exhibited higher brightness and longer lasting time than that of Sr2MgSi2O7:Eu2+, Dy3+, which could to ascribed to more traps formed by the incorporation of Ce3+. In addition, Eu2+, Dy3+ co-doped Sr2MgSi2O7 phosphors with deficient, stoichiometric or excess amounts of silicon are prepared by solid state reaction. We found that the addition of excess SiO2 into Sr2MgSi2O7:Eu2+, Dy3+ improves its photoluminescence and afterglow properties whereas SiO2 deficiencies quench its photoluminescence and afterglow. The underlying reason of photoluminescence and afterglow enhancement is discussed.In order to develop novel LLP materials, Eu activated CaMgSiO4, BaMgSiO4, Sr3Al2O5Cl2:Eu2+, R3+(R=Dy, Nd, Tm) and Pr3+ doped M2TiA2O8 (M=Sr, Ba, A=Si,Ge) were prepared and their luminescence properties were studied. The results indicate that:BaMgSiO4:Eu2+ and Sr3Al2O5Cl2:Eu2+,R3+(R= Dy, Nd, Tm) exhibited green and orange-yellow LLP; the other phosphors show no afterglow. It is worthwhile to mention that the emission of Eu2+ in CaMgSiO4 is badly quenched. In the paper, the location of the energy level of Eu2+ and the Fermi level in CaMgSiO4 was estimated to evaluate its luminescence behaviors.An important work of this paper is that ionization of Eu2+ to Eu3+ upon UV irradiation is observed in BaMgSiO4:Eu2+, but there is no indication that the photogenerated Eu3+ can change back to its divalent state at room temperature. In addition, the phosphor shows photochromism upon UV irradiation. No such photoionization and photochromism behavior is observed for the air-sintered BaMgSiO4:Eu phosphor. A possible Eu2+ photoionization mechanism is constructed on the basis of these experimental observations. The phosphorescence behaviors of Eu-doped BaMgSiO4 phosphors are discussed on the basis of the photoionization mechanism.更多还原