纳米长余辉发光材料CaTiO3∶Pr的制备及表征

以无机盐为原料,以明胶为分散介质,采用凝胶网格沉淀法制备了掺镨的钛酸钙纳米颗粒。通过热重和差热分析,讨论了CaTiO3∶Pr共沉淀及锻烧过程中的反应机理。用透射电子显微镜观测到纳米颗粒呈类球形,粒径为100 nm左右,分散性良好。利用荧光光谱分析仪对纳米CaTiO3∶Pr粉体的发光性能进行了表征。光谱数据表明：1 100℃时,煅烧1 h发光强度最大,其发光特性与传统的高温固相法相似,但烧结温度可以降低200℃。系统地研究了制备纳米CaTiO3∶Pr长余辉发光粉体的工艺条件及其影响因素,给出了最佳的制备条件。文章报道的制备方法所需装置简单,实验成本低。     

CaTiO3:Pr3+长余辉玻璃的制备与发光性能

用二次熔融法制备了CaTiO3：Pr^3＋红色长余辉玻璃。测量了样品的发射光谱,其发射光谱峰值为611．7,614．5nm,对应于Pr^3＋的4f-4f（^1D2→^3H4）跃迁,与CaTiO3：Pr^3＋晶态长余辉发光粉的发射光谱峰值相一致。玻璃粉与发光粉的质量配比在95：5～80：20时,都可以形成玻璃态并得到红色长余辉发光。研究了气氛和熔融温度对发光性能的影响,在空气环境下,800℃即可得到性能良好的样品。     

CaTiO_3∶Pr~(3+)长余辉玻璃的制备与发光性能

用二次熔融法制备了CaTiO3∶Pr3+红色长余辉玻璃。测量了样品的发射光谱,其发射光谱峰值为611.7,614.5 nm,对应于Pr3+的4 f-4 f(1D2→3H4)跃迁,与CaTiO3∶Pr3+晶态长余辉发光粉的发射光谱峰值相一致。玻璃粉与发光粉的质量配比在95∶5~80∶20时,都可以形成玻璃态并得到红色长余辉发光。研究了气氛和熔融温度对发光性能的影响,在空气环境下,800℃即可得到性能良好的样品。     

Pr3+掺杂红色长余辉发光材料研究进展

Pr3+掺杂长余辉发光材料因其稳定高效的红色持久性发光而备受关注.近年来,Pr3+掺杂红色长余辉发光材料的基础研究和应用探索均取得了长足的进步.本文总结了Pr3+离子发光特性与电荷迁移带位置的关系,概述了最近报道的发光材料体系,讨论了余辉性能的优化途径,介绍了相关材料在信息加密、交流发光二极管(AC-LED)、生物成像...     

纳米棒状长余辉材料BaAl_2O_4:Eu~(2+),Dy~(3+)的制备与发光性能

利用硝酸铝、硝酸钡、尿素为原料,以一定比例H_2O/正丁醇及H_2O/正丁醇/SBS的混合液作传递压力的介质,进行反应,然后将得到的前驱体在还原气氛下高温煅烧,得到亮度高,余辉时间长的BaAl_2O_4:Eu~(2+),Dy~(3+)纳米棒状长余辉发光材料。TEM和SEM测试表明高温煅烧后得到的BaAl_2O_4:Eu~(2+),Dy~(3+)为棒状结构,其激发光谱和发射光谱均为宽带,主发射峰分别为498 nm,是典型的Eu~(2+)5d→4f跃迁。该方法的特点在于:采用水热法合成的BaAl_2O_4:Eu~(2+),Dy~(3+)长余辉发光材料一般需经过高温煅烧,容易结块,而在合成制得的产品经1 300℃高温煅烧后仍呈现分散性良好的棒状结构,不需球磨,且发光性能良好,可直接应用。同时将2种不同的实验条件进行比较,发现在不使用表面活性剂的条件下依然可得到分散性良好的棒状BaAl_2O_4:Eu~(2+),Dy~(3+)长余辉发光材料。该制备方法有望在其他铝酸盐和硅酸盐系长余辉发光材料的制备中得到应用。     

Dy含量对红色长余辉发光材料Sr3Al2O6:Eu2+,Dy3+性能的影响

采用溶胶凝胶法制备了Sr3Al2O6:Eu2+,Dy3+红色长余辉发光材料,利用X射线衍射仪对材料的物相进行了分析,结果表明,1200℃下制备的样品的物相为Sr3Al2O6,少量的Eu和Dy掺杂没有影响样品的相组成.采用荧光分光光度计、照度计测定了样品的发光特性.结果表明Sr3Al2O6:Eu2+和Sr3Al2O6:Eu2+,Dy3+的激发光谱均为激发峰位于473 nm的宽带谱.Sr3Al2O6:Dy3+的发射峰位于530.1 nm,对应于Dy3+代替Sr2+位置后基质中形成的施主-受主对Dy·Sr-V″Sr的重新组合.Sr3-0.02-yAl2O6:0.02Eu2+,yDy3+(0相似文献   

高亮度蓝绿色长余辉材料Ba_4(Si_3O_8)_2:Eu~(2+),Pr~(3+)的发光性能及其余辉机理研究

通过高温固相法在还原气体保护下合成Ba4(Si3O8)2:Eu2+,Pr3+样品及一系列参比样品.分别利用两种模式测得光致发光与余辉光谱.结果显示:光致发光与余辉的发光中心均是Eu2+离子;共掺Pr3+在基质中引入新的俘获载流子的缺陷.热释光与余辉衰减测试表明,与单掺Eu2+所形成的陷阱深度相比,共掺Pr3+导致余辉强度增强是归因于:在浅陷阱区(T1区)的陷阱深度变得更浅.而余辉时间增长是归因于:在深陷阱区(T2区)深陷阱密度大幅度减少.同时发现在不同激发波长下激发,余辉机理中的激发路径归结于以下两种过程.其一:268 nm激发时,是基质中的电子被直接激发至陷阱.其二:330 nm或365 nm激发时,电子从Eu2+基态激发至激发态.随后部分电子通过导带运输被陷阱中心所俘获.因此,余辉强度的不同归结为以上两种载流子俘获路径的不同.     

高分子长余辉发光材料研究进展

高分子长余辉发光材料具有无定态结构、可加工性能好、发光寿命长、成本低廉等优点,对拓展纯有机长余辉发光材料的应用具有重要意义。为了实现高分子发光材料的长余辉发射,当前主要是利用杂原子或者重原子的自旋轨道耦合作用,提高单/三线态激子间的系间窜越能力;高分子基质中的氢键、卤键、离子键等分子内和分子间相互作用为磷光基团提供刚性环境,抑制其三线态激子的非辐射跃迁和猝灭。基于此,本文综述了近年来高分子长余辉发光材料的研究进展,以及在未来发展过程中面临的机遇与挑战。     

Gd3+对Ca0.8Zn0.2TiO3:Pr3+红色发光材料的敏化作用

采用溶胶-凝胶法在较低温度下合成了红色发光材料Ca0.8Zn0.2TiO3:0.002Pr3 ,xGd3 .金属离子预先溶解含有柠檬酸的乙二醇溶液中.XRD表明在800℃灼烧2h形成了钛酸盐的晶体.荧光检测结果表明所合成样品的特征激发峰为330nm、特征发射峰为614nm,分别对应于O(2p)→Ti(3d)带间跃迁和Pr3 的1D2→3H4的特征发射.样品的发光强度随x的不同而不同,发光强度增强了29%-69%.当x＝0.0005时,即nPr3 :nGd3 ＝4∶1时样品的红色发光强度最强,发光强度增强了69%.     

ZnO:Eu3+纳米晶的制备及发光性质研究

为了探讨稀土Eu3 与纳米ZnO基质之间的能量传递,利用溶胶-凝胶法(Sol-Cel)制备了ZnO:Eu3 纳米晶,测量了样品的X射线衍射谱(XRD)、光致发光谱(PL)和激发谱(PLE).X射线衍射结果表明,ZnO:Eu3 具有六角纤锌矿晶体结构.观察到稀土Eu3 强而窄的特征发射和ZnO基质弱而宽的可见发射.分析了稀土Eu3 激发态5D0→7F1,5D0→7F3和5D0→7F2特征发射机制.给出了Eu3 离子特征发射的峰值强度随掺Eu3 浓度增加而增强的变化关系,证实了纳米ZnO基质与稀土Eu3 离子之间存在能量传递.比较了Eu3 离子5D0→7Fl磁偶极跃迁(MD)与5D0→7F2电偶极跃迁(ED)的相对强度,证实了在ZnO纳米晶基质中大多数Eu3 占据了对称性较低的格位.     

Investigation on the improvement of red phosphorescence in CaTiO3:Pr3+ nanoparticles

Red phosphorescence in nanosized CaTiO₃:Pr³⁺ phosphors has been investigated by measuring the spectra of emission and excitation, as well as the charging and decay processes. The emission intensity and the persistent time have been improved. More energy traps have been observed in nanoparticles compared to the bulk powders. The integral emission intensity from the nanoparticles is remarkably greater than that from the bulk. A phosphorescence recombination mechanism through tunneling in nanoparticles is discussed.     

Photon conversion in Bi(3+)/Pr(3+)-codoped CaTiO(3)

The luminescence properties of CaTiO(3) both singly and doubly doped with Bi(3+) and Pr(3+) have been measured in different experimental conditions in order to investigate the de-excitation processes active in these materials and in particular to understand the mechanism responsible for the significant increment of the red emission observed in the codoped system upon near-ultraviolet (NUV) excitation. The steady state spectra and the decay profiles have been analyzed in the light of the possible interactions between active ions and host lattice. The general model applied to the analysis of the temporal profiles of the emission allows us to assess which are the main mechanisms involved in the Bi(3+) → Pr(3+) sensitization process.     

Zn,Cd对CaTiO3：Pr3+的发光性质的影响

采用高温固相反应合成CaTiO₃:Pr³⁺、Zn₂TiO₄、Ca_0.7Zn_0.3-xCd_xTiO₃:Pr³⁺(x=0.01,0.03,0.05,0.07,0.09,0.1)红色系列粉末状发光材料。经X射线衍射检测其结构,CaTiO₃结构为正交晶系,其结果与JCPDS标准卡(42-423)相符。Zn₂TiO₄结构属立方晶系,结果与JCPDS标准卡(25-1164)一致。Ca_0.7Zn_0.3-xCd_xTiO₃:Pr³⁺(x=0.01,0.03,0.05,0.07,0.09,0.1)由两种物相组成,一种为CaTiO₃,另一种为Zn₂TiO₄。检测了材料的激发光谱和发射光谱。发现,在CaTiO₃:Pr³⁺中加入适量Zn可形成Zn₂TiO₄相,使材料的激发光谱在324nm附近的吸收增强。少量Cd可进入Zn₂TiO₄晶格,增强激发光谱在324nm附近的吸收,同时提高发射光谱的强度;但过量的Cd的加入会导致发射光谱强度下降。     

场发射显示器用蓝色YVO_4∶Tm~(3+)纳米荧光粉的制备及性能研究

采用溶剂热法成功地制备出了YVO4∶Tm3+纳米荧光粉,并用X射线衍射仪(XRD)、透射电子显微镜(TEM)、紫外分析仪、紫外可见(UV-Vis)吸收光谱和光致发光(PL)光谱对YVO4∶Tm3+纳米荧光粉进行测试和表征。实验结果表明,YVO4∶Tm3+纳米荧光粉可发出明亮的蓝光,色纯度和发光强度都很高,而且具有良好的热稳定性。因此,YVO4∶Tm3+纳米荧光粉是一种十分适用于场发射显示器的荧光粉。     

Upconversion emission in CaTiO3:Er3+ nanocrystals

CaTiO₃:Er³⁺ (5%) nanocrystals were obtained by sol–gel method under acidic conditions. The sizes of nanocrystals were 40 nm. Strong green anti-Stokes emission was observed after excitation of the ⁴I_9/2 and ⁴I_11/2 level. The emission is due to excited state absorption (ESA) and energy transfer upconversion (ETU).     

Electronic and ionic conductivity in CaTiO3

The present work describes the electrical conductivity of undoped CaTiO₃ in terms of the electrical conductivity components corresponding to electrons, electron holes and ionic charge carriers in the temperature range 973 K — 1323 K and under controlled oxygen partial pressure (10 Pa — 72 kPa). These data are considered in terms of the transference numbers of the respective charge carriers. It appears that the ionic conductivity component assumes maximum at the n-p transition when the ionic transfer number reaches 50% of the total conductivity value at 1323 K. The present study also includes the determination of the activation energy of the conductivity component related to ions (162.1 kJ/mol), electrons (134.2 kJ/mol) and electron holes (86.2 kJ/mol). The data obtained in this work indicate that undoped CaTiO₃ exhibits a substantial level of ionic conduction that cannot be ignored in a quantitative analysis of electrical conductivity data.     

The H atom in CaTiO 3 : Structure and electronic properties

In the present work we explore the effects that an H impurity produces upon the geometry and electronic structure of the CaTiO 3 crystal considering the cubic and orthorhombic crystallographic lattices of the material. A quantum-chemical method based on the Hartree-Fock formalism and the periodic large-unit-cell model is used throughout the work. The analysis of the results shows that the interstitial H impurity binds to one of the O atoms forming the so-called O-H group. At equilibrium, the O-H distances are found to be equal to 0.89 and 1.04 Å for cubic and orthorhombic lattices respectively. Atomic displacements and relaxation energies are analysed comparing the obtained results in the cubic lattice with those in the orthorhombic lattice. In the cubic phase the computed relaxation energy of vicinity of the O-H group is found to be equal to 1.1 eV and the atomic displacements generally obey the Coulomb law. So, the negatively charged O atoms move outwards from the defective region by about 0.09 Å while the positively charged Ti and Ca atoms move towards the defective region by about 0.05 and 0.01 Å respectively. A similar effect is observed in the orthorhombic lattice of CaTiO 3 doped with an H atom. It is necessary to mention that different O positions in the orthorhombic structure are considered for the O-H bond creation. The computed relaxation energies of the atomic displacements in this structure are found to be equal to 2.3 and 2.1 eV depending on the crystallographic type of the bonding O atom.     

先兆型铁电体CaTiO3的第一性原理研究

在广义梯度近似 (GGA)下利用全电势线性化的缀加平面波法 (FPLAPW )计算了钛酸钙 (CaTiO3 )的电子结构 .将实验测得的晶胞体积记为V0 ,计算中所用的晶胞体积记为V .当V/V0 =1.0时 ,Ti离子位移为零相应于总能量低能态 ,钛酸钙不会发生铁电相变 .但如果其体积膨胀 10 % ,则Ti离子的位移将导致能量极小值 .这意味着在立方钛酸钙中有发生铁电相变的趋势 ,表明在钛酸钙中存在着体积诱发的铁电相变 ,即钛酸钙为先兆型铁电体 .态密度在V/V0 =1.1时 ,Tid电子和O(2 ) p电子之间存在强烈的轨道杂化 ,这种杂化是出现铁电性的必要条件 .电场梯度的结果也表明了这一点 .     

Temperature-dependent segregation of Pr3+ impurity ions in Y2SiO5:Pr3+ and YPO4:Pr3+ nanocrystals

Stationary and time-resolved spectroscopic methods are used to show that the impurity ions in Y₂SiO₅:Pr³⁺ and YPO₄:Pr³⁺ nanocrystals are distributed nonuniformly. This nonuniform distribution is found to be caused by the temperature-dependent segregation of Pr³⁺ ions near the surface of a nanocrystal. The motion of the activator ions from the bulk of a nanocrystal to the near-surface layer is traced when the activator concentration and the heat-treatment parameters are varied over wide ranges, and the main parameters of this effect (impurity redistribution intensity and time, diffusion coefficient) are estimated.