【作者】 杨中服；

【导师】 胡义华；

【作者基本信息】 广东工业大学 ， 应用化学， 2015， 博士

【摘要】 本文采用高温固相法合成了Ba4(Si3O8)2:Eu2+, R13+(R13+=Ho3+、Dy3+、Nd3+)、 Ba2ZnSi207:Eu2+, R23+(R23+=Ho3+、Pr3+、Dy3+)、Ba2ZnSi207:Ce3+, Tb3+和CaMgP2O7: Ce3+, Tb3+多种体系发光材料。通过XRD衍射分析确认了合成样品的物相结构,采用漫反射光谱、激发与发射光谱、荧光寿命分析以及余辉衰减等手段表征材料的发光特性,采用热释光谱分析来研究材料内部载流子陷阱的特点。具体工作如下：(1)实验研究了三价稀土离子RE3+(RE=Ho、Dy、Nd、Pr、Gd)共掺杂的Ba4(Si3O8)2:Eu2+体系,不同角度表明这些三价稀土离子的共掺杂没有引入新的发光中心,仍然以Eu2+为发光中心。Gd3+或Pr3+的共掺杂对体系的荧光和余辉属性没有明显的影响；Dy3+共掺的样品余辉与Eu2+单掺杂体系相比明显增强,肉眼可见的发光时间可以延续至半小时左右；Nd3+共掺杂可以同时增强样品的荧光和余辉发射,肉眼可见的发光时间可以延长至一小时左右；而Ho3+共掺的样品的余辉又明显强于Dy3+、Nd3+共掺的样品的余辉,时间长达10小时以上。余辉测量结果显示,共掺杂Ho3+的样品初始余辉强度达到3cd/m2。对不同样品进行了热释光测量和实验分析,发现Ba4(Si3O8)2:Eu2+, Dy3+体系具有较深的载流子陷阱,对载流子有较强的束缚,在等待时间为10小时的情况下,还有一半的载流子被束缚在深陷阱之中,因而对余辉是不利的,但是却有可能作为一种储能材料被开发利用。发现Ba4(Si3O8)2:Eu2+, Nd3+体系陷阱释放载流子的过程为二阶动力学过程,载流子的二次捕获对延长余辉时间起到了重要作用。发现Ba4(Si3O8)2:Eu2+, Ho3+体系中存在多种相近能级叠加而成的能带,具有对余辉有利的陷阱深度,同时具有较高的载流子浓度,因而表现出优异的余辉特性。(2)采用高温固相法合成了长余辉发光材料Ba2ZnSi207:Eu2+和Ba2ZnSi207:Eu2+, RE3+(RE:Ho, Pr, Dy),所有样品均呈现Eu2+的宽带发射,峰位在505nm, Pr3+、Dy3+的共掺对Eu2+的发射强度有明显的抑制作用。单掺杂的Ba2ZnSi207:Eu2+具有余辉现象,余辉持续时间为15分钟左右,共掺Ho3+可以大幅增长余辉时间至1小时,而共掺Dy3+则明显缩短余辉时间,共掺Pr3+对余辉属性没有明显改变。热释光分析表明,样品BZED内部的陷阱深度为1.252eV,对捕获载流子束缚过强,不利于载流子的释放发光,而样品BZEH即具有合适的陷阱深度(0.854eV),又具有较高的陷阱浓度,这些条件均对余辉属性有利,因而表现出较强的余辉和较长的余辉时间。(3)采用高温固相法制备了Ce3+、Tb3+稀土离子单掺杂和共掺杂的Ba2ZnSi207荧光粉体系,深入研究了该体系的荧光属性和能量传递特点。在紫外激发条件下(352nm), Ba1.98-xZnSi2O7:0.02Ce3+, xTb3+的发射既包含Ce3+的蓝光发射(428nm),也包含Tb3+离子的黄绿光发射(542nm)。通过调节Tb3+离子的掺杂浓度,体系发光的颜色可以在蓝光到绿光区域大幅变化。分析结果表明Ce3+、 Tb3+之间存在高效的非辐射能量传递,这种能量传递的机制以电偶极-偶极相互作用为主。Ce3+、Tb3+共掺杂的Ba2ZnSi207可用于近紫外LED绿光荧光粉,具有较大的研究价值和应用价值。更多还原

【Abstract】 Phosphors samples of Ba4(Si3O8)2:Eu2+, R13+(Ri3+=Ho3+, Dy3+, Nd3+), Ba2ZnSi207: Ce3+, Tb3+,Ba2ZnSi207:Eu2+, R23+(R23+=Ho3+,Pi3+,Dy3+) and CaMgP2O7:Ce3+, Tb3+ were synthesized via high temperature solid state reaction. The phase structure of samples was investigated by XRD, the luminescence property was analysed by diffuse reflectance spectra, excitation and emission spectra, fluorescence lifetimes, afterglow decay, and the carriers traps were analysed by thermoluminescence (TL). The main research results are as follows:(1) The long afterglow phosphors Ba4(Si3O8)2:Eu2+,Re3+(Re=Ho, Dy, Nd, Pr, Gd) were obtained by the high-temperature solid state reaction. Only Eu ions act as the luminescent centers in these samples, and no other luminescent center appeared with RE3+ co-doping. There is no obvious influence to the luminescence property of Ba4(Si3O8)2:Eu2+ with Pr3+ or Gd3+ co-doping. The afterglow increases with Dy3+ co-doping lasting for half hour. The fluorescence and afterglow intensities obviously magnify with Nd3+ co-doping, and the afterglow time prolongs for one hour. Ba4(Si3O8)2:Eu2+, Ho3+ shows a long-lasting phosphorescence whose duration is more than 10 h visible to the naked eyes, and the initial phosphorescence intensity is over 3cd/m2. The thermoluminescence analysis shows that the afterglow mechanism of three samples is different. Ba4(Si3O8)2:Eu2+, Dy3+ has deep traps with strong constraint to the carriers, which is disadvantageous to the afterglow property. The concentration of deep traps remains about 50% 10h later, meaning that Ba4(Si3O8)2:Eu2+, Dy3+ is an excellent phosphor material to stock up energy. The process releasing carriers of Ba4(Si3O8)2:Eu2+, Nd3+ is the second order kinetics, and the carriers are captured once again after being released which is important to prolong the afterglow time. The inner traps energy of Ba4(Si3O8)2:Eu,Ho3+is a energy band ranging from 0.608eV to 1.156eV with advantageous traps depth and large carriers concentration, deciding that Ba4(Si3O8)2:Eu2+,Ho3+ is an excellent afterglow materal.(2) Afterglow phosphors Ba2ZnSi2O7:Eu2+ and Ba2ZnSi207:Eu2+,RE3+ (RE:Ho, Pr, Dy) are synthesized by a solid state reaction. All samples show broad emission bands of Eu2+ centered at 505 nm. The fluorescence intensity is depressed obviously with Ho3+, Pr3+ or Dy3+ co-doping. Ba2ZnSi2O7:Eu2+ exhibited long-lasting phosphorescence for 15 minutes or so. Afterglow duration is 1 hour with Ho3+ co-doping and 2 minutes with Dy3+ co-doping. There is no obvious influence on the afterglow property with Pr3+ co-doping. According to the analysis of TL curves of samples, the traps depth is too deep (1.252eV) to release the trapped carriers with Dy3+ co-doping, bringing on the poor afterglow. There are suitable traps depth (0.854eV) and high concentration of trapped carriers with Ho3+ co-doping, resulting in longer afterglow duration(3) Ce3+ or Tb3+ doped and Ce3+/Tb3+ co-doped Ba2ZnSi2O7 phosphors were prepared via the conventional high temperature solid state reaction method. The photoluminescence and energy transfer properties of samples were studied in detail. Ba1.98-xZnSi2O7:0.02Ce3+,xTb3+ shows both a blue emission (428 nm) from Ce3+ and a yellowish-green emission (542 nm) from Tb3+ with considerable intensity under ultraviolet (UV) excitation (352 nm). The emission chromaticity coordinates can be adjusted from blue to green region by tuning the concentration of Tb3+ ions through an energy transfer process. The energy transfer mechanism from Ce3+ to Tb3+ ions was proved to be dipole-dipole interaction. The Ce3+ and Tb3+ co-doped Ba2ZnSi2O7 phosphors are potential UV-convertible candidates with green light emitting in UV-LEDs.更多还原