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RVO4: Ln3+ (R=La, Gd; Ln=Sm, Er, Ho, Yb/Er) microcrystals were successfully synthesized by a facile and rapid sol-gel method using glycine as the chelating agent. The crystalline structure, morphology and luminescence properties of obtained products were investigated in detail. The peaks of X-ray diffraction (XRD) patterns were well-indexed to the standard RVO4 patterns, indicating that the Ln3+ ions were well doped into the crystalline lattices and had not changed the crystalline structure. The luminescence properties of the samples are systematically studied. The typical peaks of the emission spectra were sharp and intense, revealing energy was transferred efficiently from VO4 3- to Ln3+ after excitation. The schematic diagram for energy transfer between the host matrix and doped lanthanide ions were also discussed. The chromaticity coordinates of RVO4: Ln3+ microcrystals were calculated. This work reveals that the rare-earth vanadates are potential candidates as excellent host matrices of phosphors.  相似文献   

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β-NaYF4:Ln3+ (Ln = Eu, Tb, Yb/Er, Yb/Tm) hexagonal microrods have been successfully synthesized through a facile molten salt method without any surfactant. X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy, high-resolution transmission electron microscopy, and photoluminescence spectra were used to characterize the samples. It is found that at a preferred reaction temperature of 400 °C, the structure of β-NaYF4 can gradually transform from microtubes to microrods as reaction time extends from 0.5 to 4 h. Furthermore, as the molar ratio of NaF:RE3+ (RE represents the total amount of Y3+ and the doped rare earth elements such as Eu3+, Tb3+, Yb3+/Er3+, or Yb3+/Tm3+) increased, the phase of sample transforms from YF3 into NaYF4. Under the excitation of 395 nm ultraviolet light, β-NaYF4:5 %Eu3+ shows the emission lines of Eu3+ corresponding to 5D0-3 → 7F J (J = 1–4) transitions from 400 to 700 nm, resulting in red down-conversion (DC) light emission. When doped with 5 % Tb3+ ions, the strong DC fluorescence corresponding to 5D4 → 7F J (J = 6, 5, 4, 3) transitions with 5D4 → 7F J (green emission at 544 nm) being the most prominent group that has been observed. Moreover, upon 980 nm laser diode excitation, the Yb3+/Er3+- and Yb3+,Tm3+- co-doped β-NaYF4 samples exhibit bright yellow and blue upconversion (UC) luminescence, respectively, by two- or three-photon UC process. The luminescence mechanisms for the doped lanthanide ions were thoroughly analyzed.  相似文献   

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BiPO4:Ce3+ and BiPO4:(Ce3+, Tb3+) powders were synthesized by the method of precipitation. The X-ray diffraction patterns show that BiPO4:Ce3+ and BiPO4:(Ce3+, Tb3+) samples have pure hexagonal phases. The transmission electron microscopy results show that the synthesized samples are nanoparticles. Ethylene glycol plays an important role in the formation of nanoparticles. The excitation spectrum of BiPO4:Ce3+ sample shows the transition from the ground 2 F 5/2 state to the excited 5d states of the Ce3+ ions. The emission spectrum exhibits a strong band centered at 352 nm originating from the 5d → 4f transitions of the Ce3+ ions. The emission spectrum of the BiPO4:(Ce3+, Tb3+) sample contains both a weak emission band of the Ce3+ ions and strong green emission bands of the Tb3+ ions. The excitation and emission spectra show that there are energy transfers between Ce3+ and Tb3+ ions in the BiPO4:(Ce3+, Tb3+) sample. The energy transfers between Ce3+ and Tb3+ ions improve the emission efficiency of BiPO4:(Ce3+, Tb3+) sample.  相似文献   

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Ln-doped Sb2Te3 (Ln: Lu3+, Er3+, Ho3+) nanomaterials were synthesised by a co-reduction method in hydrothermal condition. Powder X-ray diffraction (XRD) patterns indicate that the LnxSb2?xTe3 crystals (Ln = Lu3+, x = 0.00–0.06; Er3+ and Ho3+ x = 0.00–0.04) are isostructural with Sb2Te3. The cell parameter a decreases for LnxSb2?xTe3 compounds upon increasing the dopant content (x), while c increases. Scanning electron microscopy and transmission electron microscopy images show that doping of Lu3+ and Ho3+ ions in the lattice of Sb2Te3 results in spherical nanoparticles while that in Er3+ leads to hexagonal nanoplates, respectively. The electrical conductivity of Ln-doped Sb2Te3 is higher than that of pure Sb2Te3 and increases with temperature. By increasing the concentration of Ln3+ ions, the absorption spectrum of Sb2Te3 shows red shifts and some intensity changes. In addition to the characteristic red emission peaks of Sb2Te3, emission spectra of doped materials show other emission bands originating from ff transitions of the Ho3+ ions.  相似文献   

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LnBaFeCoO5 + δ (Ln = Nd, Sm, Gd) layered oxides have been synthesized and their crystal structure, thermal stability, thermal expansion, electrical conductivity, thermoelectric power, and magnetic susceptibility have been studied. The oxides have a tetragonal structure (sp. gr. P4/mmm) with unit-cell parameters a = 0.3909(2) nm and c = 0.7695(6) nm for Ln = Nd (δ = 0.65), a = 0.3908(3) nm and c = 0.7662(6) nm for Ln = Sm (δ = 0.37), and a = 0.3908(2) nm and c = 0.7613(6) nm for Ln = Gd (δ = 0.37). The LnBaFeCoO5 + δ compounds are antiferromagnetic p-type semiconductors. With decreasing Ln3+ ionic radius, their electrical conductivity and linear thermal expansion coefficient decrease and their thermoelectric power and antiferromagnetic ordering temperature increase. Near 518–653 K, the linear thermal expansion coefficient of the LnBaFeCoO5 + δ oxides increases from (12.9–16.6) × 10?6 to (19.3–26.5) × 10?6 K?1, which is due to the release of weakly bound oxygen from the oxides. We have determined parameters of charge transport in the [Fe(Co)O2] layers in the crystal structure of the LnBaFeCoO5 + δ phases.  相似文献   

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Xiong  F. B.  Luo  X.  Yang  W. B.  Yang  Y.  Lin  H. F.  Meng  X. G.  Ma  E.  Zhu  W. Z. 《Journal of Materials Science: Materials in Electronics》2022,33(5):2619-2630
Journal of Materials Science: Materials in Electronics - Efficiently red-emitting Pr3+-doped LnNbO4 (Ln?=?La, Gd, and Y) phosphors have been successfully prepared by the traditional...  相似文献   

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Rare earth cerium oxides (Ln2Ce2O7, Ln = La, Nd, Sm, and Gd) with cubic-fluorite structure were prepared by hydrothermal method using cetyltrimethyl ammonium bromide as surfactant. X-ray diffraction (XRD), thermogravimetric analysis/differential scanning calorimetry (TG/DSC), Raman spectroscopy, and field emission scanning electron microscopy (FESEM) were utilized to characterize the phase structure, thermal decomposition, and morphology of the products, respectively. Qualitative analyses indicate that the as-prepared products are fluorite-type structures. The lattice parameter and average crystallite size of the products are closely related to the ionic radii. The activation energy of crystal growth shows an increasing trend with the decrease in ionic radii. The sintering behavior of compacted body was also investigated, revealing that the sintering-resistance properties of Ln2Ce2O7 are descending as the order of La2Ce2O7, Nd2Ce2O7, Sm2Ce2O7, and Gd2Ce2O7.  相似文献   

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Ln0.6Sr0.4Co0.8Fe0.2O3 – (Ln = La, Pr, Nd, Sm) solid solutions are prepared by a procedure which makes it possible to markedly reduce the synthesis temperature and duration. X-ray diffraction, microstructural analysis, and density measurements are used to optimize conditions for the fabrication of dense substituted-cobaltite ceramics.  相似文献   

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Erbium doped β-Ga(2)O(3) nanowires and microwires have been obtained by a vapour-solid process from an initial mixture of Ga(2)O(3) and Er(2)O(3) powders. X-ray diffraction (XRD) analysis reveals the presence of erbium gallium garnet as well as β-Ga(2)O(3) phases in the microwires. Scanning electron microscopy (SEM) images show that the larger microwires have a nearly rectangular cross-section. Transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) analysis show good crystal quality of the β-Ga(2)O(3) nanowires. The nanostructures have been studied by means of the cathodoluminescence technique in the scanning electron microscope. Er intraionic blue, green and red emission lines are observed in luminescence spectra even at room temperature, which confirms the optical activity of the rare earth ions in?the grown structures. Mapping of the main 555?nm emission intensity shows a non-homogeneous distribution of Er ions in the microstructures.  相似文献   

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By introducing Ti vacancies in advance for charge compensation, single cubic perveskite rare-earth doped strontium titanate ceramics with the formula Re 0.02Sr0.98Ti0.995O3 (Re–STO, Re = Pr, Nd, Gd) were prepared via solid-state reaction method. All Re–STO ceramics sintered at 1,410 °C in air for 3 h showed a similar dense microstructure with the grain size lower than 10 μm. The room temperature dielectric constant ε r of Re–STO ceramics was higher than 3,000 (@ 1 kHz) and changed <8 % within the applied bias electric field. Especially, the room temperature dielectric loss tanδ of Re–STO ceramics was lower than 0.02 (@ 1 kHz), and the average breakdown strength E b surpassed 14 kV/mm, demonstrating that Re–STO ceramics could be very promising for high-voltage capacitor applications. The temperature stability of the ε r of Re–STO ceramics was evaluated in a temperature range of ?50 to 200 °C. Meanwhile, the energy storage density of Re–STO ceramics was investigated as a function of the applied bias electric field.  相似文献   

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Radiochemistry - The interaction of synthetic skupite UO3·2.25H2O with aqueous solutions of La, Ce, Pr, Nd, Sm, Eu,Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu nitrates under hydrothermal conditions at a...  相似文献   

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Polycrystalline LnTiTaO6 (Ln = Ce, Pr, Sm) compounds were prepared in the solid state ceramic route. The powders were calcined between 1250 °C and 1300 °C and sintered between 1480 °C and 1520 °C. The materials were characterized by XRD and SEM. The dielectric properties were measured in the frequency range 1 kHz–5 MHz. The absorption spectra and photoluminescence spectra of the samples were analysed. The materials are useful as gain media in micro lasers because of the optical absorption and photoluminescence.  相似文献   

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Lattice effect on magnetic and electrical transport properties of Ln2/3Pb1/3MnO3 (Ln=La, Pr, Nd) films prepared by RF magnetron sputtering technique were investigated. With the decrease of the average ions radius 〈rA〉, the structure of Ln2/3Pb1/3MnO3 (Ln=La, Pr, Nd) targets transit from the rhombohedral phase to the orthorhombic phase, and the Curie temperature reduces rapidly with the decrease of 〈rA〉. The electrical properties show that films are the metallic state which can be fitted to the formula: ρ(T)=ρ0 + ρ1T^2 + ρ2T^4.5 at low temperatures. The temperature range of the ferromagnetic metallic state becomes narrow with the decrease of 〈rA〉. The phenomenon can be explained by the lattice effect.  相似文献   

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The synthesis of BaLn2(1?x)ZnO5:2xTb3+ (Ln = Y, Gd) nanophosphors using solution combustion method with an aim to study the effect of sintering temperature and Tb3+ ions concentration on the luminescent properties has been investigated. Under UV excitation, BaY2(1?x)ZnO5 and BaGd2(1?x)ZnO5 nanoparticles exhibit apparent characteristic green emission from 5D4 state to 7F6?3 states of Tb3+ ions with the strongest at 544 nm. Luminescence concentration quenching could be observed when the Tb3+ ions contents were more than 4 mol% in both nanophosphors. The luminescence decay curves suggest monoexponential behavior of both nanophosphors. X-ray diffraction results confirmed the single-phased orthorhombic structure of both powders belonging to space group Pbnm. TEM analysis indicates the spherical morphology of nanoparticles with average grain size in the range of 85–95 nm. BaY2(1?x)Tb2x ZnO5 and BaGd2(1?x)Tb2x ZnO5 nanophosphors may have potential applications in field emission displays based on their uniform shape, low-cost synthetic route, and diverse luminescent properties.  相似文献   

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Investigation of the oxygen-deficient 112-type ordered oxides of the type LnBaCoMnO5+δ (Ln = Nd, Eu) evidences certain unusual magnetic behavior at low temperatures, compared to the LnBaCo2O5+δ cobaltites. The ordered NdBaCoMnO5.9 depicts a clear paramagnetic to antiferromagnetic type transition around 220 K, whereas for EuBaCoMnO5.7 one observes an unusual magnetic behavior below 177 K which consists of ferromagnetic regions embedded in an antiferromagnetic matrix. The existence of two sorts of crystallographic sites for Co/Mn and their mixed valence states favor the ferromagnetic interaction, whereas antiferromagnetism originates from the Co3+–O–Co3+ and Mn4+–O–Mn4+ interactions. Unlike the parent compounds, the present Mn-substituted phases do not exhibit prominent magnetoresistance effects in the temperature range 75–400 K.  相似文献   

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Er3+ and Pr3+ codoped fluorotellurite glasses has been synthesized. The PL spectrum revealed that the intensity of Er3+ characteristic emission was enhanced as Pr3+ concentration increased. Due to small mismatch between the energy level of Er3+: 4F7/2 and Pr3+: 3P0 resonant energy was possibly transferred between them. While Pr3+ concentration kept increasing, both Pr3+ and Er3+ concentration quenching occurred. These glasses with the controllable CIE coordinates might be a potential candidate for the widely application such as solid state multicolor display.  相似文献   

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