Red phosphors in MgAl2Si2O8 doping with Mn4+, Gd3+ and Lu3+ and host-sensitized luminescence properties

Mn⁴⁺ doped and Gd³⁺, Lu³⁺ co-doped MgAl₂Si₂O₈-based phosphors were first of all synthesized by solid state reaction at about 1300.0 °C. They were characterized by thermogravimetry, differential thermal analysis, X-ray powder diffraction, photoluminescence, and scanning electron microscopy. The luminescence mechanism of the phosphors which showed broad red emission bands in the range of 610–715 nm and had a different maximum intensity when activated by UV illumination was discussed. Such a red emission can be attributed to the intrinsic ²E → ⁴A₂ transitions of Mn⁴⁺.     

Photo and Thermo‐luminescence Properties of Mn4+, Ce4+ and Sm3+ in MgAl2Si2O8 Phosphor

Mn⁴⁺, Ce⁴⁺ and Sm³⁺ doped MgAl₂Si₂O₈‐based phosphors were synthesized at 1300 °C by solid state reaction and characterized by thermogravimetry (TG), differential thermal analysis (DTA), X‐ray powder diffraction (XRD), photoluminescence (PL), thermoluminescence (TL) and scanning electron microscopy (SEM). The phosphors showed broad red emission bands in the range of 610–715 nm and different maximum intensity when activated by UV illumination. Such a red emission can be attributed to the intrinsic ²E→⁴A₂ transitions of Mn⁴⁺.     

Mn4+-, Tb3+,4+-, and Er3+-activated red phosphors in the MgAl2Si2O8 system

Mn⁴⁺ doped and Tb^3+,4+, Er³⁺ co-doped MgAl₂Si₂O₈-based phosphors were prepared by conventional solid-state synthesis at 1,300 °C. They were characterized by thermogravimetry, differential thermal analysis, X-ray powder diffraction, photoluminescence, and scanning electron microscopy. The luminescence mechanism of the phosphors, which showed broad red emission bands in the range of 600–715 nm and had different maximum intensities when activated by UV illumination, was discussed. Such a red emission can be attributed to the intrinsic ²E → ⁴A₂ transitions of Mn⁴⁺.     

Investigation of Luminescence Properties of Eu3+, Dy3+ and Gd3+ Doped MgAl2Si2O8 Red‐emitting Phosphors

Rare‐earth‐doped aluminosilicates of alkaline earth MgAl₂Si₂O₈: Eu³⁺, Dy³⁺ and MgAl₂Si₂O₈: Eu³⁺, Gd³⁺ were synthesized by the solid state reaction method at 1300 ^oC. The phosphors were characterized by X‐ray powder diffraction (XRD), photoluminescence (PL), thermoluminescence (TL) and scanning electron microscopy (SEM). X‐ray powder diffraction studies show that the phosphors were crystallized in the triclinic crystal system. The phosphors show characteristic broad band phosphorescence of Eu³⁺. This broad band phosphorescence has red emission bands in the range of 580–705 nm corresponding to ⁵D₀ → ⁷F_j (j:0,2,3,4) transitions of Eu³⁺.     

尖晶石型四氧化三锰中 Mn2+、Mn3+、Mn4+的测定方法和离子分布的研究

采用选择性溶解法和计算法结合的方法,测定了四氧化三锰中Ｍｎ＾２＋、Ｍｎ＾３＋、Ｍｎ＾４＋的含量,求出了四氧化三锰中的锰氧摩尔比和三种不同价态的锰离子在尖晶石中的离子分布式,进而确定其结构。分析结果与ＸＲＤ谱图吻合。     

Eu2+和Pb2+离子在Sr4Si3O8Cl4中发光的研究

本文研究了Sr₄Si₃O₈Cl₄基质的物理化学性质和以Eu^<2+、Ph²⁺离子为激活剂的荧光体的发射光谱、激发光谱、反射光谱及激活剂浓度对发光性能的影响。     

A new emission band of Eu2+ and its efficient energy transfer to Mn2+ in Sr2Mg3P4O15:Mn2+, Eu2+

Eu(2+) singly and Eu(2+), Mn(2+) co-doped Sr(2)Mg(3)P(4)O(15) exhibit not only the well known blue emission band of Eu(2+) peaking at 448 nm but also a new band at 399 nm in violet. They are attributed to Eu(2+) on different Sr(2+) sites. The Eu(2+) for the violet band can transfer energy to the red emitting Mn(2+) more efficiently than Eu(2+) for the blue band. The new Eu(2+) band could enable Sr(2)Mg(3)P(4)O(15):Mn(2+), Eu(2+) to be a promising phosphor for enriching the red component of white LEDs.     

Tuning the photoinduced O2-evolving reactivity of Mn4O47+, Mn4O46+, and Mn4O3(OH)6+ manganese-oxo cubane complexes

The manganese-oxo "cubane" core complex Mn(4)O(4)L(1)(6) (1, L(1) = Ph(2)PO(2-)), a partial model of the photosynthetic water oxidation site, was shown previously to undergo photodissociation in the gas phase by releasing one phosphinate anion, an O(2) molecule, and the intact butterfly core cation (Mn(4)O(2)L(1)(5+)). Herein, we investigate the photochemistry and electronic structure of a series of manganese-oxo cubane complexes: [Mn(4)O(4)L(2)(6)] (2), 1(+)(ClO(4-)), 2(+)(ClO(4-)), and Mn(4)O(3)(OH)L(1)(6) (1H). We report the atomic structure of [Mn(4)O(4)L(2)(6)](ClO(4)), 2(+)(ClO(4-)) [L(2) = (4-MeOPh)(2)PO(2-)]. UV photoexcitation of a charge-transfer band dissociates one phosphinate, two core oxygen atoms, and the Mn(4)O(2)L(5)(+) butterfly as the dominant (or exclusive) photoreaction of all cubane derivatives in the gas phase, with relative yields: 1H > 2 > 1 > 2(+) > 1(+). The photodissociation yield increases upon (1) reducing the core oxidation state by hydrogenation of a corner oxo (1H), (2) increasing the electron donation from the phosphinate ligand (L(2)), and (3) reducing the net charge from +1 to 0. The experimental Mn-O bond lengths and Mn-O bond strengths and the calculated ligand binding energy explain these trends in terms of weaker binding of phosphinate L(2) versus L(1) by 14.7 kcal/mol and stronger Mn-(mu(3)-O)(core) bonds in the oxidized complexes 2(+) and 1(+) versus 2 and 1. The calculated electronic structure accounts for these trends in terms of the binding energy and antibonding Mn-O(core) and Mn-O'(ligand) character of the degenerate highest occupied molecular orbital (HOMO), including (1) energetic destabilization of the HOMO of 2 relative to 1 by 0.75 eV and (2) depopulation of the antibonding HOMO and increased ionic binding in 1(+) and 2(+) versus 1 and 2.     

Ce3+、Tb3+离子及Ce3+-Tb3+离子对在Sr4Si3O8Cl4基质中发光的研究

研究了Ce³⁺、Tb³⁺、离子及Ce³⁺-Tb³⁺离子对在Sr₄Si₃O₈Cl₄基质中的发射光谱和激发光谱。初步讨论了Ce³⁺、Tb³⁺离子之间发光敏化的机理。     

Sorption of microamounts of Ce3+, Pm3+, Eu3+, Gd3+ and Yb3+ on aluminium hydroxide

The sorption of microamounts of trivalent lanthanides (Ln³⁺) on freshly precipitated Al(OH)₃ has been measured in dependence on pH and the time of sorption. Also, the influence of organic complexing ligands and inorganic electrolytes on the sorption process has been investigated. The mechanism of sorption is discussed. Freshly precipitated Al(OH)₃ can be used for the preconcentration of microamounts of trivalent lanthanides. However, the preconcentration is not quantitative in the presence of high concentrations of complexing ligands (citrate and similar) which form strong complexes with Ln³⁺ ions.     

Eu3+- and Ho3+-doped Ba3Al2O6- and MgAl2O4-type phosphors and their photoluminescent properties

Journal of Thermal Analysis and Calorimetry - The aluminate hosts were basically activated with the Eu3+- and Ho3+-ions which were prepared by solid-state reaction in this study. The DTA/TG results...     

On the phosphorescence mechanism in SrAl2O4:Eu2+ and its codoped derivatives

The mechanism of phosphorescence in SrAl₂O₄:Eu,Dy material is discussed on the basis of a thermo-activated release of electrons trapped at oxygen vacancy sites. The depths and concentration of the electron traps are strongly affected by codoping with trivalent lanthanide cations Ln³⁺. This finding is rationalized by comparing the ionization potentials of the dopant cation Eu²⁺, the codopant cation Ln³⁺ and the substituted cation Sr²⁺. Such a use of ionization potentials provides a practical guide with which the variation of the phosphorescent decay time in the codoped derivatives of SrAl₂O₄:Eu is predicted.     

沸石中组装SrAl2O4:Eu2+,Dy3+的可调发光现象

首先用溶胶-凝胶法制备符合SrAl2O4：Eu^2 ,Dy^3 化学组成的溶胶,然后通过机械研磨、水热反应和微波加热反应三种不同的组装方法和微波还原扩散法使其进入主体ZSM-5沸石的孔道中。主客体材料的荧光光谱出现显著蓝移,余辉光谱出现400nm和517nm两个发射峰,两个余辉峰的相对发射强度随组装方法和组装浓度的改变而具有可调性,呈现有规律的变化。分析其原因是由于发光材料进入沸石的纳米级孔洞引起的。     

SrAl2O4∶Eu2+，Dy3+纳米长余辉发光材料的制备与表征

采用溶胶-凝胶法制备了SrAl₂O₄∶Eu²⁺，Dy³⁺ 纳米长余辉发光材料，研究了pH值、反应温度和络合剂等对溶胶-凝胶形成的影响，研究了灼烧温度对SrAl₂O₄∶Eu²⁺，Dy³⁺ 晶相、颗粒尺度和发光性能的影响。利用XRD, SEM，光谱分析等手段对产物进行了结构和性能分析。实验结果表明，在800 ℃时SrAl₂O₄晶相开始形成但没有发光，而在1 100 ℃烧结的样品则具有很好的发光性能。样品平均晶粒尺寸随灼烧温度升高而增加，平均晶粒尺寸为20～40 nm。样品的激发光谱是峰值在240，330，378和425 nm的连续宽带谱，发光光谱是峰值在523nm的宽带谱，与SrAl₂O₄∶Eu²⁺，Dy³⁺ 粗晶材料相比，发光光谱发生了“红移”现象。样品的热释光峰值位于157 ℃，与SrAl₂O₄∶Eu²⁺，Dy³⁺ 粗晶材料相比，峰值向低温移动了13℃。     

SrAl2O4∶Eu2+，Dy3+晶格点缺陷的形成及其在发光材料中的作用

采用高温固相法合成了具有不同点缺陷的SrAl₂O₄∶Eu²⁺，Dy³⁺发光粉。通过余辉衰减特性、激发光谱与热致发光性能测试，研究了晶格点缺陷在发光材料中的作用。结果表明，Dy_Sr^·对长余辉发光性能有很大的影响，可以作为具有合适深度的电子陷阱；氧离子空位(V_O^··)不能作为具有合适深度的电子陷阱，但可增加电子陷阱Dy^{3+相似文献}   

Facile synthesis and multicolor luminescent properties of uniform Lu2O3:Ln (Ln=Eu3+, Tb3+, Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+) nanospheres

Multicolor Lu(2)O(3):Ln (Ln=Eu(3+), Tb(3+), Yb(3+)/Er(3+), Yb(3+)/Tm(3+), and Yb(3+)/Ho(3+)) nanocrystals (NCs) with uniform spherical morphology were prepared through a facile urea-assisted homogeneous precipitation method followed by a subsequent calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectrum (EDS), Fourier transformed infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), and photoluminescence (PL) spectra as well as kinetic decays were employed to characterize these samples. The XRD results reveal that the as-prepared nanospheres can be well indexed to cubic Lu(2)O(3) phase with high purity. The SEM images show the obtained Lu(2)O(3):Ln samples consist of regular nanospheres with the mean diameter of 95 nm. And the possible formation mechanism is also proposed. Upon ultraviolet (UV) excitation, Lu(2)O(3):Ln (Ln=Eu(3+) and Tb(3+)) NCs exhibit bright red (Eu(3+), (5)D(0)→(7)F(2)), and green (Tb(3+), (5)D(4)→(7)F(5)) down-conversion (DC) emissions. Under 980 nm NIR irradiation, Lu(2)O(3):Ln (Ln=Yb(3+)/Er(3+), Yb(3+)/Tm(3+), and Yb(3+)/Ho(3+)) NCs display the typical up-conversion (UC) emissions of green (Er(3+), (4)S(3/2),(2)H(11/2)→(4)I(15/2)), blue (Tm(3+), (1)G(4)→(3)H(6)) and yellow-green (Ho(3+), (5)F(4), (5)S(2)→(5)I(8)), respectively.     

Eu3+在Ba2TiSi2O8中的发光

红色荧光材料主要有(碱土)硫化物体系[1,2],(碱土)钛酸盐体系[3,4],氧化稀土体系[5],硅酸盐体系[6]以及其它氧化物体系如MO∶Eu~(3 )(M=Ca、Sr、Ba)[7],SrAl2O4∶Eu~(2 )[8]等。在这些体系中,主要以Eu3 做激活     

Thermoluminescence study of persistent luminescence materials: Eu2+- and R3+-doped calcium aluminates, CaAl2O4:Eu2+,R3+

Thermoluminescence properties of the Eu2+-, R3+-doped calcium aluminate materials, CaAl2O4:Eu2+,R3+, were studied above room temperature. The trap depths were estimated with the aid of the preheating and initial rise methods. The seemingly simple glow curve of CaAl2O4:Eu2+ peaking at ca. 80 degrees C was found to correspond to several traps. The Nd3+ and Tm3+ ions, which enhance most the intensity of the high-temperature TL peaks, form the most suitable traps for intense and long-lasting persistent luminescence, too. The location of the 4f and 5d ground levels of the R3+ and R2+ ions were deduced in relation to the band structure of CaAl2O4. No clear correlation was found between the trap depths and the R3+ or R2+ level locations. The traps may thus involve more complex mechanisms than the simple charge transfer to (or from) the R3+ ions. A new persistent luminescence mechanism presented is based on the photoionization of the electrons from Eu2+ to the conduction band followed by the electron trapping to an oxygen vacancy, which is aggregated with a calcium vacancy and a R3+ ion. The migration of the electron from one trap to another and also to the aggregated R3+ ion forming R2+ (or R3+-e-) is then occurring. The reverse process of a release of the electron from traps to Eu2+ will produce the persistent luminescence. The ability of the R3+ ions to trap electrons is probably based on the different reduction potentials and size of the R3+ ions. Hole trapping to a calcium vacancy and/or the R3+ ion may also occur. The mechanism presented can also explain why Na+, Sm3+, and Yb3+ suppress the persistent luminescence.