稀土激活的新型氧化物上转换材料研究

【作者】 李婷；

【导师】 郭崇峰；

【作者基本信息】 西北大学 ， 光学， 2014， 博士

【摘要】 稀土掺杂的上转换荧光材料在照明与显示、生物荧光标记、太阳能电池、光学温度传感等方面具有潜在应用。本文以获得高效稳定的上转换荧光材料为目的,选择双钼酸盐和铟酸盐为基质、稀土离子为激活剂,采用溶胶-凝胶技术合成了具有优异上转换发光特性的材料,并系统研究了荧光强度与合成方法、工艺参数、基质组成、掺杂离子浓度、激发光功率、共掺杂离子等的依赖关系。并对其上转换发光机制、发光颜色的调控及上转换效率的提高进行了深入研究,着重讨论了Yb3+离子对不同稀土离子上转换发光过程中的能量传递作用。制备了Er3+, Yb3+共掺的ALn(MoO4)2(A=Li, Na, K, Ag; Ln=La, Gd, Y)绿色荧光粉,系统研究了荧光强度对制备方法、合成工艺参数、掺杂离子浓度和基质组成的依赖关系,结果表明,溶胶-凝胶法制备的样品比传统高温固相法具有更高的发光强度。以LiLa(MoO4)2为基质时上转换发光最强；以其为基质,采用共掺杂技术实现了上转换红、绿、蓝三色发光,通过Ho3+, Tm3+, Yb3+离子的合理配比实现对三色荧光比的调控,获得了单一波长泵浦的上转换白光发射。首次研究了以具有较低声子能量的CaIn2O4为基质的上转换发光材料。合成了具有红、绿双色发射的CaIn2O4:Er3+, Yb3+上转换荧光粉,Er3+和Yb3+浓度的增加导致了发射红绿比的增加,进而获得色度可调的上转换荧光发射。通过对Er3+单掺的样品和Er3+,Yb3+共掺的样品的发射光谱比较、荧光强度与泵浦功率的依赖关系以及寿命测试阐明了样品的上转换发光机理和Yb3+对Er3+离子的能量传递作用。制备了Ho3+单掺和Ho3+, Yb3+共掺的CaIn2O4绿色上转换荧光粉,研究了制备方法、合成条件、掺杂浓度、泵浦功率对样品发光强度的影响,讨论了其上转换机制。结果表明,Ho3+离子的红光发射为双光子过程,绿光发射为双光子和三光子过程同时存在。溶胶-凝胶法制备的样品的发射强度是高温固相法制备的样品的12倍,Yb3+离子的加入对Ho3+离子的上转换发射具有良好的敏化作用。对具有最佳组成的CaIn2O4:0.1Yb3+,0.005Ho3+的上转换效率测试表明,上转换效率随着激发光功率的增加逐渐增加,在功率达到1.5W时上转换效率达5.5%,是迄今为止有报道的上转换荧光材料中效率最高的。充分表明,CaIn2O4:Yb3+/Ho3+是一种高效的上转换绿光发射材料。合成了CaIn2O4:RE3+和CaIn2O4:RE3+, Yb3+(RE=Tm, Pr, Nd)荧光粉,研究了样品的可见光上转换荧光特性,通过荧光光谱比较说明Tm3+, Pr3+, Nd3+的上转换发射过程中Yb3+离子对Tm3+, Pr3+, Nd3+的能量传递起着主要作用。荧光光强和激发光功率的依赖关系研究表明Tm3+、Nd3+的上转换发射为三光子过程而Pr3+离子为双光子和三光子过程同时存在。在Er3+, Yb3+离子双掺的CaIn2O4中引入Li+离子,使样品的上转换荧光强度得到明显增强。分析Li+离子掺杂对荧光粉上转换增强的原因可能有Li+的电荷补偿作用、Li2CO3的助熔作用以及Li+带来的晶格畸变。更多还原

【Abstract】 Rare earth doped upconversion luminescent (UCL) materials have potential applications in solid state lighting and display, bio-label, solar cell and optical temperature sensor, et al. The focus of this paper is searching for novel efficient rare earth doped oxide UC material with high stability. Double molybdates were selected as the hosts and rare earth ions were used as activators. Their dependences of luminescence intensity on the synthesis method, technological parameters, host composition, dopant concentration, pumping power and other doped ions were studied systematically. The UC mechanisms, the tunable emission color and the enhancement of UCL efficiency of the phosphors were investigated intensively. The energy transfer processes from Yb3+to other rare earth ions were emphasized.Er3+, Yb3+codoped ALn(MoO4)2(A=Li, Na, K, Ag; Ln=La, Gd, Y) phosphor with green emission were prepared. The dependence of UCL intensity on the synthesis method, parameter, dopant concentration and matrices were investigated. Results indicate that the phosphors prepared by sol-gel method show stronger intensity than that of samples synthesized by solid state method. The strongest UCL intensity was obtained in LiLa(MoO4)2, and the tricolor (red, green and blue) UC emissions were obtained by co-doping different rare earth ions in this matrix. UC white light emitting were realized through adjusting the ratio of tricolor emission intensity by changing concentration of Ho3+, Tm3+and Yb3+.The UCL properties of rare earth doped CaIn2O4host with low phonon energy were investigated for the first time. CaIn2O4:Er3+, Yb3+phosphor with red and green bicolor emissions were synthesized. The increase of Er3+and Yb3+concentration leads to the increase of the ratio of red to green emission intensity, and tunable emission color could be obtained. The UC mechanism were illuminated and the energy transfer from Yb3+to Er3+were proved through comparison of UCL spectra of Er3+single doped and Er3+, Yb3+co-doped sample, the dependence of UC intensity on the pumping power and the fluorescence lifetime measurement.Ho3+single and Ho3+, Yb3+co-doped CaIn2O4with efficient UC green emission were synthesized. The influence of synthesis condition, dopant concentration and pumping power to the luminescent intensity were studied and the UC mechanism was discussed. The results indicate that the red emission is two photon process and the green emission includes two photon and three photon process. The UCL intensity of sample synthesized by sol-gel method is12times stronger than that of sample prepared by solid-state method. The introduction of Yb3+has enhanced the UCL of Ho3+greatly due to the effective energy transfer from Yb3+to Ho3+. The UC efficiency measurement of Caln2O4:0.1Yb3+,0.005Ho3+with optimal doping concentration indicates that the UC efficiency increases with the increasing of pump power and reaches the maximum value about5.5%at1.5W. This manifests that CaIn2O4:Yb3+, Ho3+is an efficient UC green emitting phosphor.CaIn2O4:RE3+and CaIn2O4:RE3+, Yb3+(RE=Tm, Pr, Nd) phosphors were prepared and their UC luminescent properties were investigated. The spectra comparison indicates that the the energy transfer from Yb3+to RE3+play an important role in the process of UC emissions of RE3+(Tm3+, Pr3+, Nd3+). The relation between intensity and pump power indicate that UC emissions of Tm3+, Nd3+are three photon process and UC emissions of Pr3+is the mixing of two and three photon processes under the excitation of980nm laser.Li+ions were introduced to Er3+, Yb3+co-doped CaIn2O4and UCL enhancement was achieved obviously. The possible reasons of the intensity enhancement include the charge compensation effect of Li+, the fluxing action of Li2CO3as well as the matrix distortion caused by Li+更多还原