Optical characterization of Sm3+ and Dy3+:ZnO-PbO-B2O3 glasses

Here, we present the results of the analysis of Sm(3+) or Dy(3+) (0.5 mol%) ions doped heavy metal oxide (HMO)-based zinc lead borate (ZLB) glasses. Optical measurements such as absorption, emission spectra, lifetimes, XRD, DSC profiles have been carried out. The emission spectrum of Sm(3+):ZLB has shown the emission transitions of (4)G(5/2)-->(6)H(5/2) (563 nm), (4)G(5/2)-->(6)H(7/2) (598 nm), (4)G(5/2)-->(6)H(9/2) (646 nm), (4)G(5/2)-->(6)H(11/2) (708 nm) with lambda(exc): 401 nm ((6)H(5/2)-->(4)F(7/2)). In the case of the Dy(3+):ZLB glass, emission transitions of (4)F(9/2)-->(6)H(15/2) (485 nm), (4)F(9/2)-->(6)H(13/2) (575 nm) and (4)F(9/2)-->(6)H(11/2) (664 nm) with lambda(exi): 447 nm ((6)H(15/2)-->(4)I(15/2)) have been identified. Energy level schemes relating to the emission mechanisms involved in Sm(3+) and Dy(3+) glasses have been given.     

Luminescence properties of Dy3+ or/and Sm3+ doped LiLa(WO4)2 phosphors and energy transfer from Dy3+ to Sm3+

The Dy³⁺ or/and Sm³⁺ doped LiLa(WO₄)₂ phosphors are synthesized by a facile solid state reaction method. The phase and luminescence properties of the phosphors are investigated. The powder X-ray diffraction (XRD) results show that the phosphor has a tetragonal phase crystal structure. The quenching concentration of single doped Dy³⁺ and Sm³⁺ in the LiLa(WO₄)₂ are determined to be 6% and 3%, respectively. Under the excitation of 404 nm, warm white light is obtained in the co-doped phosphors. With the concentration of Sm³⁺ increasing, the correlated color temperature (CCT) gradually decreases from 3090 to 2453 K. Two kinds of energy transfer may exist at the same time. The overlap between the emission spectrum of Dy³⁺ and the excitation spectrum of Sm³⁺ reveals that the energy of Dy³⁺ can transfer to Sm³⁺ via radiation. Another way of energy transfer, that is non-radiative energy transfer, is attributed to the excited state of Dy³⁺ (⁴F_9/2) slightly higher than that of Sm³⁺ (⁴I_19/2). The calculation results show that non-radiative energy transfer process from Dy³⁺ to Sm³⁺ ions is predominated by quadrupole–quadrupole interaction.     

Sr2SiO4∶Dy3+材料制备及发光特性

采用高温固相法制备了Sr2SiO4∶Dy3+发光材料. 在365 nm紫外光激发下, 测得Sr2SiO4∶Dy3+材料的发射光谱为一个多峰宽谱, 主峰分别为486, 575和665 nm; 监测575 nm的发射峰, 所得材料的激发光谱为一个多峰宽谱, 主峰分别为331, 361, 371, 397, 435, 461和478 nm. 研究了Dy3+掺杂浓度对Sr2SiO4∶Dy3+材料发射光谱强度的影响. 研究结果显示, 随着Dy3+浓度的增大, 黄、蓝发射峰比值(Y/B)也逐渐增大; 随着Dy3+浓度的增大, 575 nm发射峰强度先增大后减小. 加入电荷补偿剂Li+, Na+和K+均提高了Sr2SiO4∶Dy3+材料的发射光谱强度, 其中以Li+的情况最为明显.     

Monodisperse and core-shell-structured SiO2@YBO3:Eu3+ spherical particles: synthesis and characterization

Y0.9Eu0.1BO3 phosphor layers were deposited on monodisperse SiO2 particles of different sizes (300, 570, 900, and 1200 nm) via a sol-gel process, resulting in the formation of core-shell-structured SiO2@Y0.9Eu0.1BO3 particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL), and cathodoluminescence (CL) spectra as well as lifetimes were employed to characterize the resulting composite particles. The results of XRD, FE-SEM, and TEM indicate that the 800 degrees C annealed sample consists of crystalline YBO3 shells and amorphous SiO2 cores, in spherical shape with a narrow size distribution. Under UV (240 nm) and VUV (172 nm) light or electron beam (1-6 kV) excitation, these particles show the characteristic 5D0-7F1-4 orange-red emission lines of Eu3+ with a quantum yield ranging from 36% (one-layer Y0.9Eu0.1BO3 on SiO2) to 54% (four-layer Y0.9Eu0.1BO3 on SiO2). The luminescence properties (emission intensity and color coordinates) of Eu3+ ions in the core-shell particles can be tuned by the coating number of Y0.9Eu0.1BO3 layers and SiO2 core particle size to some extent, pointing out the great potential for these particles applied in displaying and lightening fields.     

Preparation of Sr2CeO4:Eu3+,Dy3+ white luminescence phosphor particles and thin films by using an emulsion liquid membrane system

Sr(2)CeO(4) and Sr(2)CeO(4):Eu(3+),Dy(3+) phosphor particles and thin films were prepared by using an emulsion liquid membrane (ELM, water-in-oil-in-water (W/O/W) emulsion) system, containing VA-10 (2-methyl-2-ethylheptanoic acid) as extractant (cation carrier). A two-step extraction enabled efficient extraction for Sr(3+) and rare earth ions, and the resulting precursor metal oxalate particles produced in the internal water phase of the ELM system were about 60 nm in diameter. Calcination of the oxalate particles in air gave submicrometer-sized Sr(2)CeO(4) and Sr(2)CeO(4):Eu(3+),Dy(3+) particles, which showed blue and white luminescence, respectively, by UV excitation. Blue and white luminescence phosphor thin films were also prepared by soaking alumina substrates into the W/O emulsion containing precursor oxalate particles, followed by calcination in air.     

Preferential suppression of high-energy upconverted emissions of Tm3+ by Dy3+ ions in Tm3+/Dy3+/Yb3+-doped LiYF4 colloidal nanocrystals

The intensity of high energy UV and blue upconverted emissions of Tm(3+) ions in Tm(3+)/Yb(3+) co-doped LiYF(4) colloidal nanocrystals was selectively reduced compared to the NIR emission at 802 nm. This was achieved by doping a small amount of Dy(3+) ions into the host matrix.     

Efficient X-ray generation of Sm2+ in nanocrystalline BaFCl/Sm3+: a photoluminescent X-ray storage phosphor

Efficient X-ray generation of relatively stable Sm2+ centers is observed in nanocrystalline Sm3+-activated BaFCl, as prepared by a one-step wet chemical reaction. The conversion efficiency is approximately 50,000 times higher than that in microcrystalline BaFCl/Sm3+ prepared at 900 degrees C. The Sm2+ centers, and hence the radiation dose, can be directly monitored by the narrow photoexcited 5DJ-7FJ f-f luminescence lines. The relatively high efficiency of Sm2+ generation appears to be directly linked to the particle size.     

Synthesis and characterization of novel blue emitting Na2CaSiO4:Ce3+ phosphor

The blue phosphors Na_(2?x)Ca_(1?x)SiO₄:xCe³⁺ were synthesized by the sol–gel method and their luminescence characteristics were investigated for the first time. Structural information about prepared samples is obtained by analyzing the XRD patterns and SEM micrographs. The photoluminescence (PL) excitation spectra indicate that the Na_(2?x)Ca_(1?x)SiO₄:xCe³⁺ phosphors can be effectively excited by ultraviolet (360 nm) light. The PL emission spectra exhibit tunable blue broadband emission with the dominant wavelength of 427–447 nm under excitation of 360 nm by controlling the doping concentration of Ce³⁺. The concentration quenching effect for Ce³⁺ was found at the optimum doping concentration of 4 mol%. The Commission Internationale de l’Eclairage 1931 chromaticity coordinates of Na_1.96Ca_0.96SiO₄:0.04Ce³⁺ are (0.1447, 0.0787), which are better color purity compared to the commercial Eu²⁺-doped BaMgAl₁₀O₁₇ phosphor. Na_1.96Ca_0.96SiO₄:0.04Ce³⁺ composition shows intense blue emission (peak wavelength, 439 nm) with relative intensity versus commercial BaMgAl₁₀O₁₇:Eu²⁺ blue phosphor (Nichia) 65 and 158 % under 254 and 365 nm excitation, respectively. All the results indicate that Na_(2?x)Ca_(1?x)SiO₄:xCe³⁺ phosphors are potential candidate as a blue emitting phosphor for UV-converting white light-emitting diodes.     

溶胶凝胶模板法制备SiO2:Sm3+纳米阵列材料

采用溶胶凝胶模板法制备了不同Sm3+掺量的SiO2:Sm3+纳米阵列材料,通过SEM、EDS、FTIR等对材料的形貌和结构进行测试表征.FTIR分析表明Sm3+进入SiO2网络结构形成了Si-O-Sm键.SEM、EDS分析显示Sm3+掺量的增大促使阵列由纳米管向纳米线的转变.此外,腐蚀清洗等后处理工艺对保持纳米阵列的形貌至关重要.最后,讨论了溶胶凝胶模板法制备SiO2;Sm3+纳米阵列的机理.     

Synthesis and optical properties of Gd2O3:Pr3+ phosphor particles

Spherical-shaped Gd₂O₃:Pr³⁺ phosphor particles were prepared with different concentrations of Pr³⁺ using the urea homogeneous precipitation method. The resulting Gd₂O₃:Pr³⁺ phosphor particles were characterized by X-ray diffraction, field emission scanning electron microscope, and photoluminescence spectroscopy. The effects of the Pr³⁺ doping concentration on the luminescent properties of Gd₂O₃:Pr³⁺ phosphors were investigated. Photoluminescence measurements revealed the Gd₂O₃:1?% Pr³⁺ phosphor particles to have the strongest emission. The luminescence properties of Gd₂O₃:Pr³⁺ particles are strongly affected by the phosphor crystallinity and X-ray diffraction measurements confirmed that the crystallinity of Gd₂O₃ cubic structure could be enhanced by increasing the firing temperature. The luminescent Gd₂O₃:Pr³⁺ phosphor particles have potential applications in areas, such as optical display systems, lamps and etc.     

Reddish-orange,neutral and warm white emissions in Eu3+, Dy3+ and Dy3+/Eu3+ doped CdO-GeO2-TeO2 glasses

Eu³⁺, Dy³⁺ and Dy³⁺/Eu³⁺ doped CdO-GeO₂-TeO₂ glasses were prepared using the melt-quenching process and analyzed by X-diffraction, Raman spectroscopy, excitation and emission spectra, and emission decay time profiles. The lack of X ray diffraction peaks revealed that all samples are amorphous. Vibrational modes associated with TeOTe and GeOGe related bonds and molecular oxygen were detected by Raman spectroscopy. The luminescence characteristics were studied upon excitations that correspond with the emission of InGaN (370–420 nm) based LEDs. The Eu³⁺ singly doped glass displayed reddish-orange global emission, with x = 0.601 and y = 0.349 CIE1931 chromaticity coordinates, upon 393 nm excitation. Neutral emission with x = 0.373 and y = 0.412 CIE1931 chromaticity coordinates and correlated color temperature (CCT) of 4400 K, was achieved in the Dy³⁺ singly doped glass excited at 388 nm. The Dy³⁺/Eu³⁺ co-doped glass exhibited warm, neutral and soft warm white emissions with CCT values of 3435, 4153 and 2740 K, under excitations at 382, 388 and 393 nm, respectively, depending mainly on the Dy³⁺ and Eu³⁺ relative excitation. The Dy³⁺ excitation bands observed in the Dy³⁺/Eu³⁺ glass by monitoring the 611 nm Eu³⁺ emission, suggest that Dy³⁺ → Eu³⁺ energy transfer takes place, despite the fact that the Dy³⁺ emission decays in the Dy³⁺ and Dy³⁺/Eu³⁺ doped glass, remain without changes. The shortening of Eu³⁺ decay in presence of Dy³⁺ was attributed to an Eu³⁺ → Dy³⁺ non-radiative energy transfer process, which according with the Inokuti-Hirayama model might be dominated through an electric quadrupole-quadrupole interaction, with efficiency and probability of 5.5% and 51.6 s⁻¹, respectively.     

Precipitation preparation and luminescence of phosphor YAl3 (BO3)4 : Eu3+

以化学沉淀法制备单相的铕离子掺杂硼铝酸盐红色荧光粉YAl3(BO3)4:Eu3+,考察了焙烧温度、掺铕量等因素对材料性能的影响,用X射线衍射、扫描电镜、激发光谱和发射光谱对荧光粉的结构、形貌和发光性能进行了表征.以尿素为沉淀剂,900℃焙烧沉淀前驱体可得到单相荧光粉YAl3 (BO3)4:Eu3+,反应温度比传统高温固相法降低了300℃;沉淀法制备的荧光粉粒径分布范围小,无团聚现象,粒径约300 nm.掺铕量为10％(物质的量比)时发光强度最大.在260 nm的紫外光激发下,Eu3+的5D0→7F2的电偶极跃迁最强,发射光为618nm的红光.     

Preparation, characterization and photoluminescence properties of BaB2O4: Eu3+ red phosphor

A new red emitting BaB2O4: Eu3+ phosphor was synthesized by solid-state reaction method. X-ray powder diffraction (XRD) analysis confirmed the monoclinic formation of BaB2O4. Field-emission scanning electron-microscopy (FE-SEM) observation indicated that the microstructure of the phosphor consisted of irregular grains with heavy agglomerate phenomena. Upon excitation with 394 nm light, the BaB2O4: Eu3+ phosphor shows bright red emissions with the highest photoluminescence (PL) intensity at 611 nm due to 5D0→7F2 transitions of Eu3+ ions. The CIE chromaticity coordinates are calculated from the emission spectrum to be x=0.64, y=0.35. The effects of the Eu3+ concentration on the PL were investigated. The results showed that the optimum concentration of Eu3+ in BaB2O4 host is 6 mol% and the dipole-dipole interaction plays the major role in the mechanism of concentration quenching of Eu3+ in BaB2O4: Eu3+ phosphor. The effect of charge compensation on the emission intensity was also studied. The charge compensations of Li+, Na+ and K+ anions all increased the luminescent intensity of BaB2O4: Eu3+. K+ anion gave the best improvement to enhance the intensity of the emission, indicating K+ is the optimal charge compensator. All properties show that this phosphor could serve as a potential candidate for application as a red phosphor for NUV chip LED.     

Improved water resistance of SrAl2O4: Eu2+, Dy3+ phosphor directly achieved in a water-containing medium

In this paper, a heterogeneous precipitation method utilizing urea hydrolysis was adopted to coat a SiO₂ layer on the surface of SrAl₂O₄:Eu²⁺, Dy³⁺ long persistence phosphors. To avoid phosphor hydrolysis in a water-containing coating medium, the hydrolysis and polymerization reactions of tetraethyl orthosilicate (TEOS) were concerned and carried out. The crystal phases, surface morphologies, hydrolysis stability and water resistance on afterglow properties of coated phosphors were investigated. Scanning electron microscopy, energy dispersive spectrum analysis, transmission electron microscope and Fourier transform infrared spectrum results confirmed that a continuous, uniform and compact SiO₂ coating layer was successfully obtained on the phosphors surface. A theoretical coating amount of 5% or higher was found to be good for hydrolysis stability. Photoluminescence results revealed the coated phosphors showed much better water resistance on afterglow properties than the uncoated phosphor. We also discussed and proposed the hydrolysis restriction mechanism of SrAl₂O₄:Eu²⁺, Dy³⁺ in the water-containing coating medium.     

The electrical conductivity of Dy3+/Sc3+ co-doped CeO2 solid electrolytes

Journal of Solid State Electrochemistry - The Dy3+ single doped and Dy3+/Sc3+ co-doped CeO2 electrolyte powders were successfully synthesized by a sol–gel method followed by calcination at...     

Co~(2+)/Dy~(3+)掺杂纳米立方Fe_3O_4的热还原制备及磁靶向滞留性能

采用热还原沉淀法制备了一系列Co~(2+)/Dy~(3+)掺杂的纳米立方MxFe3-xO4磁性颗粒.利用X射线衍射仪、透射电子显微镜和振动样品磁强计研究了不同含量掺杂离子对MxFe3-xO4晶体结构、形貌及磁性的影响.研究发现,掺杂未改变母体的对称性,但母体形貌逐渐从立方体向球体过渡;Co~(2+)和Dy~(3+)的掺杂对于铁氧体磁学性质的影响明显不同,当Co~(2+)实际掺杂量为0.44和Dy~(3+)实际掺杂量为0.05时,MxFe3-xO4立方磁性粒子的饱和磁化强度(Ms)达到最大值,分别为76.65和70.21 A·m2·kg-1.与超顺磁性Fe_3O_4球体相比,高磁性掺杂Fe_3O_4立方体在体外模拟磁流体磁靶向定位实验中显示出较高的滞留率.     

Sm3Cl[SiO4]2: Ein chlorarmes Chloridorthosilicat des Samariums

Sm₃Cl[SiO₄]₂: A Chlorine‐poor Chloride Orthosilicate of Samarium Pale yellow, plate‐like single crystals of Sm₃Cl[SiO₄]₂ (orthorhombic, Pnma; a = 701.74(8), b = 1800.8(2), c = 626.63(7) pm; Z = 4) are obtained upon the reaction of SmCl₃, Sm₂O₃ and SiO₂ (”︁Kieselgel”︁”︁) in 1 : 4 : 6 molar ratios, most advantageously in the presence of substantial amounts of NaCl as fluxing agent, after seven days at 850 °C in evacuated silica ampoules. The B‐type crystal structure (isotypic with e. g. Yb₃Cl[SiO₄]₂) contains discrete orthosilicate tetrahedra [SiO₄]^4– which form anionic double layers ({(Sm1)₂[SiO₄]₂}^2–) with (Sm1)³⁺. These are alternatingly sheethed along [010] with cationic monolayers ({(Sm2)Cl}²⁺) consisting of (Sm2)³⁺ and Cl^–. Both crystallographically independent Sm³⁺ cations exhibit coordination numbers of eight (Sm1: 1 Cl + 7 O; Sm2: 2 Cl + 6 O) with respect to the involved electronegative particles.     

Spectroscopic investigation of La7Ta3W4O30:Sm3+ orange-red phosphor for white LEDs

The novel orange-red light emitting La₇Ta₃W₄O₃₀:xSm³⁺ (x = 0.005–0.20) phosphors were synthesized via the solid-state reaction method. The crystal structure, photoluminescence (PL) properties, optimum concentration, color purity, decay life, and thermal stability of the samples were systematically studied. Under the excitation of 404 nm, La₇Ta₃W₄O₃₀:Sm³⁺ emits intense orange-red light at 597 nm. The PL spectra of La₇Ta₃W₄O₃₀:Sm³⁺ phosphors are ascribed to the ⁴G_5/2 to ⁶H_J (J = 5/2, 7/2, 9/2, and 11/2) transitions of Sm³⁺ ions. The concentration quenching occurs at the doping level of 1 mol%. The quenching temperature is higher than 500 K. Finally, a white LED (w-LED) with the Commission Internationale de L'Eclairage (CIE) chromaticity coordinates of (0.312, 0.296) and good color rendering index (Ra) of 86 was fabricated. As a consequence, all the results suggest that the orange-red phosphors La₇Ta₃W₄O₃₀:Sm³⁺ have potential applications in w-LEDs structures.     

Preparation and luminescence properties of green-light-emitting afterglow phosphor Ca8Mg(SiO4)4Cl2:Eu2+

Green-light-emitting long-lasting phosphorescence phosphor, Eu²⁺ activated calcium magnesium chlorosilicate Ca₈Mg(SiO₄)₄Cl₂, has been prepared by a modified solid-state reaction method using Ca₂SiO₄:Eu²⁺ as a precursor. Its properties have been discussed and analyzed utilizing XRD, photoluminescence, excited-state decay curve and long-lasting phosphorescence decay curve. Upon UV light excitation, the emission spectrum of Ca₈Mg(SiO₄)₄Cl₂:Eu²⁺ phosphor is composed of two separate bands centered at 425 nm and 505 nm, respectively. Furthermore, after irradiation by a 320-nm UV light for 3 min, the 2% Eu²⁺-doped Ca₈Mg(SiO₄)₄Cl₂ phosphor emits intense green-light-emitting afterglow from the 4f⁶5d¹→4f⁷ transition of Eu²⁺, and its afterglow can be seen with the naked eye in the dark clearly for more than 3 h after removal of the excitation source. The disappearance of the high-energy 425 nm band in the afterglow emission spectrum is explained by its different crystallographic sites. The afterglow decay curve of the Eu²⁺-doped Ca₈Mg(SiO₄)₄Cl₂ phosphor contains a fast decay component and another slow decay one. The possible mechanism of this long-lasting phosphorescence phosphor is also discussed based on the experimental results.     

Energy Transfer from Ce3+ to Tb3+/Dy3+/Mn2+ in Ca9Ga(PO4)7 Phosphors: Synthesis,Structure and Tunable Multicolor Luminescent Properties

A series of Ca₉Ga(PO₄)₇:Ce³⁺/Tb³⁺/Dy³⁺/Mn²⁺ phosphors with tunable color, in which Ce³⁺ acts as the sensitizer, was synthesized. Energy transfer (ET) from Ce³⁺ to Tb³⁺/Dy³⁺/Mn²⁺ was investigated in detail. Tb³⁺/Dy³⁺/Mn²⁺ single-doped Ca₉Ga(PO₄)₇ can exhibit green, yellow, and red emission, respectively. Incorporating Ce³⁺ into a Tb³⁺/Dy³⁺/Mn²⁺ single-doped Ca₉Ga(PO₄)₇ phosphor can remarkably promote the luminous efficiency of the Tb³⁺/Dy³⁺/Mn²⁺ ions. This enhancement originates from an efficient ET from Ce³⁺ to Tb³⁺/Dy³⁺/Mn²⁺. The ET was validated by luminescence spectra, decay dynamics, and schematic energy levels. Moreover, the intensity ratio of red emission of Mn²⁺ to violet emission of Ce³⁺ was analyzed based on energy-transfer and lifetime measurements. In Ce³⁺-Tb³⁺, Ce³⁺-Dy³⁺, and Ce³⁺-Mn²⁺ doped Ca₉Ga(PO₄)₇, the emitting color changed from violet to green, yellow, and red, respectively, which indicates the potential use of this new tunable phosphor in UV light-emitting diodes.