【摘要】 基于量子剪裁基本原理,通过光谱技术研究NaGdF4∶Tm3+,Dy3+在一个真空紫外光子激发下获得两个蓝色光子的可能性。在这种化合物中,量子剪裁通过下转换,即通过应用不同镧系离子间的能量传递进行。通过对Tm 4 f12-4 f115d激发,部分能量从Tm3+离子5d态直接传递给Gd3+,然后在Gd3+-Tm3+之间发生交叉弛豫,剩余能量从Gd3+传递给Dy3+,产生两个可见光子发射,一个来自Tm3+的1G43-H6跃迁,另一个来自Dy3+的4F9/26-H15/2跃迁。主要研究获得以NaGdF4∶Tm3+,Dy3+为基础的新型具有更高效率,更高稳定性和更强真空紫外(VUV)吸收量子剪裁发光粉的可能性。各种光谱技术,如光致发光、激发和衰减等被用来表征不同Dy3+浓度掺杂NaGdF4中Gd3+晶格间能量迁移引起的施主Gd3+和受主Dy3+之间的能量传递。结果表明Gd3+离子之间存在能量迁移,随之交换相互作用引起施主与受主(Gd3+-Dy3+)之间的能量传递。通过Bursh-tein等人关于激发态的弛豫理论,施主-受主能量传递参数kDS可以从Gd3+的6P7/2发射的衰减计算出。Gd3-Dy3+能量传递量子效率也可以得到。NaGdF4∶Tm3+和NaGdF4∶Tm3+,Dy3+是由水热法制备的,NaGdF4∶Dy3+是由文献[4]方法制备的。发射光谱和激发光谱通过自制的VUV光谱仪和F-4500测量。衰减曲线由OPO激光器激发获得Gd3+-Dy3+之间能量传递量子效率在受主浓度大约在NA=0.6%时达到最佳值,并且明显地观测到浓度猝灭效应。更多还原

【Abstract】 The possibility to obtain two blue photons under excitation of one VUV photon in NaGdF4∶Tm3+,Dy3+ has been investigated by means of spectroscopic techniques,based on quantum cutting principle.In this compound visible quantum cutting is achieved through downconversion,i.e.,by making use of energy transfer between different lanthanide ions.Upon VUV excitation in the 4f105d levels of Tm3+,part of the energy is transferred directly from the Tm3+ 4f105d states to Gd3+.The cross-relaxation between Gd3+-Tm3+ is followed,and then the left energy is transferred from Gd3+ to Dy3+.Two visible photons are yielded: one from Tm3+ due to 1G4→3H6 transition,and one from Dy3+ due to 4F9/2→6H15/2 transition.In this paper,the possibility to obtain a new quantum cutting phosphor with higher efficiency,higher stability and higher VUV absorption based on NaGdF4∶Tm3+,Dy3+ has been investigated.The spectroscopic techniques,including luminescent emission,excitation,decay,etc.were performed to characterize the donor Gd3+ ion-acceptor Dy3+ ion energy transfer preceded by energy migration among Gd3+ lattices in NaGdF4 doped with different concentrations of Dy3+ ions.It is shown by the results that the Gd3+-Dy3+ transfer preceded by energy migration among the Gd3+ ions is mainly governed by the exchange interaction.By the theory on excited state relaxation processes,which was developed by Burshtein et al.,the donor-acceptor energy transfer parameter kDA can be calculated from the 6P7/2 emission decay of Gd3+.The quantum efficiency of Gd3+-Dy3+ energy transfer was derived as well.Powders of NaGdF4∶Tm3+(1.5%) and NaGdF4∶Tm3+(1.5%),Dy3+(0.3%) were prepared by the hydrothermal technique,and NaGdF4∶ Dy3+(0.3%,0.6%,1%,3% and 5 %) by the method described in Ref.[4].The emission and excitation spectra were measured by home-made VUV spectrometer and F4500 monochromator.The decay curves were obtained under excitation of OPO laser.The quantum efficiencies for the Gd3+-Dy3+ energy transfer have an optimal value for acceptor concentrations at about NA=0.6% and concentration quenching can be observed obviously.更多还原