Xinyu Ye

Structure and luminescence properties of Sm 3+ doped Y 2 MoO 6 phosphor under near ultraviolet light excitation

Abstract A series of Sm 3+ doped Y 2 MoO 6 were prepared through high temperature solid state reaction technique. Their phase structures, morphologies and luminescence properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectrometry. The most intense absorption of Y 2 MoO 6 host occurred at 367 nm. Energy transfer from host lattice to Sm 3+ ions could be observed, and the schematic diagram of energy transfer was constructed. The critical energy transfer distance and energy transfer mechanism between Sm 3+ ions were discussed in detail. Considering the high color purity and appropriate emission intensity, Sm 3+ doped Y 2 MoO 6 could be a promising phosphor under near ultraviolet light excitation.

Photoluminescence enhancement of YAG:Ce3+ phosphor prepared by co-precipitation-rheological phase method

Abstract YAG:Ce 3+ phosphor was prepared by a novel co-precipitation-rheological phase method. The resulting YAG:Ce 3+ phosphor was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescent emission spectra. By using acetic acid as solvent, YAG:Ce 3+ powder with small particle size (≤2 μm) was obtained at a relatively lower sintering temperature of 1400 °C. With the content of acetic acid increasing, small particles dissolved and disappeared, but larger particles grew up and changed its shape from spherical to partially rectangular. Meanwhile, the emission intensity of the sample prepared by co-precipitation-rheological phase method was about 43% higher than that of the sample prepared by co-precipitation method. It was assumed that the significant improvement of luminescence was mainly because the rheological phase presented a better diffusion environment, and therefore, a better homogeneity of activators of Ce 3+ .

Synthesis mechanism of Sm2Fe17 alloy produced in reduction-diffusion process

Sm2Fe17 alloy was the precursor of Sm2Fe17Nx magnetic materials. Reduction-diffusion (R/D) method was a new preparation process for the Sm2Fe17 alloy, and had been widely employed as a new preparation method for rare earth-transition metal intermetallic compounds. In this text, thermodynamics and kinetics for the synthesis of the Sm2Fe17 alloy by reduction-diffusion (R/D) method in the Ca-Sm2O3-Fe system were analyzed. The related synthesis mechanism of this reaction was investigated in detail by means of scanning electron microscope (SEM). The results showed that the thickness of the Sm2Fe17 alloy layer versus the reaction time could be fit by the parabola law, and its growth model was determined to be: (L0-L)2=43.848 t, the diffusion of Sm into Fe proceeded with the formation of the Sm2Fe17 phase from the very beginning of the reaction, and rich samarium phases, such as SmFe2 and SmFe3, were not formed, and the rate-determining step of the R/D reaction was found to be the peritectic reaction between liquid samarium and solid iron.

Re-determination of the crystal structure of Ca2Y8Si6O26 and study on the luminescent properties of Ca2Y8Si6O26:Tb3+

Abstract The crystal structure of silicate oxyapatite Ca2Y8Si6O26 was indexed as hexagonal, space group P63/m, α=0.93515 nm, c=0.67872 nm, α=β=90°, γ=120°, V=0.5138692 nm3. Three strong peaks located at 32.079°, 32.595°, and 50.104° with d=2.7903, 2.74649, 1.8194 was in accordance with (211), (112), and (213) planes. The optimum concentration of Tb3+ in Ca2Y8Si6O26 to yield highest photoluminescence intensity was 10 mol.% of Y3+. The corresponding excitation spectrum consisted of an intense broad band from 220 to 260 nm. The photoluminescence measurements showed that the green emission originated from 5D4−7F5 was predominant in the measured range with strong doublet lines at 543 and 549 nm.

Single-phase full-color Ba3Lu2(SiO4)3:Eu2+ phosphor for white-light emitting diodes

Abstract We developed a new silicate-based full-color phosphor Ba 3 Lu 2 (SiO 4 ) 3 :Eu 2+ through solid state reaction. The host crystal structure was isostructural with Ca 3 Y 2 (SiO 4 ) 3 instead of garnet-type. The phosphor absorbed near-ultraviolet light from 250 to 400 nm, which was very suitable for a color converter of white LED that used UV-LED as the primary light source. The photoluminescence peak wavelength of Ba 3 Lu 2 (SiO 4 ) 3 :Eu 2+ was about 461 nm and a shoulder peak was around 522 nm, which resulted from the 5d-4f transition of the Eu 2+ . The optimum concentration of Eu 2+ was 3.45 mol.% of Ba 2+ content in Ba 3 Lu 2 (SiO 4 ) 3 host. It is a promising candidate for application in white LED as a white light converter.

Characterization and photoluminescence of Lu2O3-Eu3+ nano-phosphor prepared by modified solution combustion method

Abstract Nanoscale Lu 2 O 3 :Eu 3+ phosphor was prepared by a modified solution combustion method using urea and acrylamide monomer. The particle sizes and photoluminescent properties of nano-phosphor were closely related to the molar ratio of urea-to-RE nitrates and acrylamide monomer-to-RE nitrates. The as-prepared samples with the sizes of 9.6-11.6 nm were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive spectrometer. Lu 2 O 3 :Eu 3+ nano-phosphor that depicted high photoluminescence in the size around 10 nm was reported. Compared with the sample prepared by solid state reaction, the photoluminescence of sample was increased sufficiently to be 45.1%. The emission spectra of the samples presented the typical emission from 5 D 0 level to 7 F J ( J =0, 1, 2, 3, 4) level of the Eu 3+ ion.

A modified solution combustion method to superfine Gd2O3:Eu3+ phosphor: preparation, phase transformation and optical properties

Abstract Cubic and monoclinic Gd 2 O 3 :Eu 3+ phosphors in the range of nano-scale and submicron-scale were prepared by a modified solution combustion method. Coexistence of cubic and monoclinic phases was found in the highest luminescent sample synthesized at 600 °C. In relation to commercial sample, the relative luminescence intensity was 49.8%. The shape of emission spectrum of the sample thus changed and the charge-transfer-state band of excitation spectrum slightly shift toward higher energies. With increasing the annealing temperature, phase transformation and correlative optical properties of Gd 2 O 3 :Eu 3+ phosphors were studied. It was found that the samples were dominated by cubic structure and monoclinic structure at temperatures below and above 900 °C.

Influence of synthetic temperature and heating time on the luminescence behavior of M5(PO4)3Cl:Eu2+,Mn2+ (M=Ca, Sr) phosphors

Abstract To further understand the energy loss mechanism of the “charge transfer process” that was proposed in our previous work on Eu 2+ -Mn 2+ co-doped phosphors, the influence of synthetic temperature and heating time on the photoluminescence (PL) behavior of M 5 (PO 4 ) 3 Cl:Eu 2+ ,Mn 2+ (M=Ca, Sr) phosphors was investigated by analyzing their PL spectra and decay curves. For the Ca phase, an increase in the synthetic temperature resulted in an increase in the loss from the “charge transfer process” since more Eu 2+ ions were involved in the Eu 2+ -Mn 2+ clusters. This was contrary to the thermodynamic expectation. To solve this contradiction, we proposed that the formation of Eu 2+ -Mn 2+ clusters was kinetically blocked at lower synthetic temperatures. With an increase in heating time for the phosphors synthesized at lower temperature (such as 1100 °C) the PL intensity decreased, which supported the above assertion.

Experimental study and thermodynamic calculation of Lu2O3-SiO2 binary system

Abstract As a binary system of BaO-Lu 2 O 3 -SiO 2 ternary system, Lu 2 O 3 -SiO 2 system was optimized and calculated by CALPHAD approach based on available phase diagram and relevant thermodynamic data of RE 2 O 3 -SiO 2 (RE=Lu, Yb, Y) binary systems as well as our experimental data of Lu 2 O 3 -SiO 2 system obtained by quenching experiment. The Gibbs free energy of high temperature solution was described by an ionic two-sublattice model as (Lu 3+ ) P (O 2– , SiO 2 0 ) Q . The calculated phase diagram below 1873 K was in good agreement with experimental data at 1573, 1773 and 1873 K. The calculated Gibbs energies of two intermediate phases Lu 2 SiO 5 and Lu 2 Si 2 O 7 , the activity of Lu 2 O 3 and SiO 2 and specific heat capacities of intermediate phases agreed well with experimental results of Y 2 O 3 -SiO 2 system. This tentative study will offer help for the research of single-phase phosphor and related metallurgical slags, refractories, high-temperature superconductivity material systems.