National Engineering Research Center for Ionic Rare Earth

Ganzhou, China

National Engineering Research Center for Ionic Rare Earth

Ganzhou, China

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Ye X.,Jiangxi University of Science and Technology | Ye X.,National Engineering Research Center for Ionic Rare Earth | Luo Y.,Jiangxi University of Science and Technology | Liu S.,Jiangxi University of Science and Technology | And 2 more authors.
Journal of Alloys and Compounds | Year: 2017

A series of novel Er3+ doped and Er3+/Yb3+ co-doped Ba3Lu4O9 phosphors were synthesized by a simple high-temperature solid-state reaction method. The crystal structure and morphology of the samples were identified by XRD and SEM analysis. Under 980 nm laser diode excitation, the green (at 537 nm and 560 nm) and red (at 660 nm) UC emission were observed, which could be attributed to the (2H11/2, 4S3/2)→4I15/2 and 4F9/2 → 4I15/2 transitions, respectively. The UC luminescence can be finely tuned from green to dark-yellow light to some extent by increasing Yb3+ doping concentration. The sintering temperature and doping concentration of Ba3Lu4-x-yO9: x Er3+, y Yb3+ were optimized to x = 0.1 and y = 0.6 at 1550 °C. The emission intensity ratio of Green/Red keeps declining monotonically with increasing Er3+ or Yb3+ concentration, which is due to the cross-relaxation effect and cooperative energy transfer between the two neighboring Er3+ ions-as well as back energy transfer from Er3+ to Yb3+ ions. Based on the pump-power dependence and UC luminescence decay curves, the energy level diagram and the possible energy transfer mechanism of Er3+ doped as well as Er3+/Yb3+ co-doped system were investigated in detail. In addition, according to the energy gap law, the possibilities of non-radiative transition between parts of energy levels of Er3+ ions were calculated. © 2017 Elsevier B.V.


Wu D.,National Engineering Research Center for Ionic Rare Earth | Wu D.,Ganzhou Nonferrous Metallurgy Research Institute | Ye X.-Y.,National Engineering Research Center for Ionic Rare Earth | Ye X.-Y.,Jiangxi University of Science and Technology | And 9 more authors.
Key Engineering Materials | Year: 2017

Sc0.88-xLu0.05VO4:Eu3+ 0.07,Bi3+ x(0≤x≤0.05) red phosphors were synthesized by solid state reaction at 1200°C for 3h. The structure, morphology and luminescence spectra of samples are investigated by X-ray diffraction (XRD), Scanning electron microscope (SEM) and fluorescence spectrophotometer, respectively. The samples doped with Eu3+, Lu3+ and Bi3+ maintain the body-centered tetragonal structure of ScVO4 and the morphology remains essentially unchanged with slight agglomeration. The excitation spectrum of Sc0.88-xLu0.05VO4:Eu3+ 0.07,Bi3+ x emerged redshift and the excitation intensity increase within the near UV excitation(360-400nm). The optimum doping concentration of Bi3+ is 0.02(x value), and the maximum emission intensity of Sc0.86Lu0.05VO4:Eu3+ 0.07,Bi3+ 0.02 is higher than 88 % in comparison with Sc0.88Lu0.05VO4:Eu3+ 0.07 under 365 nm excitation. Decay curve of 5D0 state for as-prepared samples fits the single order exponential behavior, the lifetime of 5D0 increase first and then decrease with the increase of Bi3+ doping concentration. The internal quantum efficiency is up to 74.08% under 365nm excitation; When the temperature raises to 200°C the emission intensity maintains 79% of that in the room temperature. Sc0.86Lu0.05VO4:Eu3+ 0.07,Bi3+ 0.02 phosphor show high internal quantum efficiency and thermal stability, which is suitable for the UV-pumped white LED as red phosphor. © 2017 Trans Tech Publications.


Luo Y.,Jiangxi University of Science and Technology | Jiang J.-Q.,Jiangxi University of Science and Technology | Hou D.-J.,Jiangxi University of Science and Technology | You W.-X.,Jiangxi University of Science and Technology | And 2 more authors.
Faguang Xuebao/Chinese Journal of Luminescence | Year: 2015

Na2TiF6: Mn4+ red phosphors with different Mn4+ doping mole fraction were synthesized by the co-precipitation method. Structure, morphology, photoluminescence excitation and emission spectra as well as decay curve of Na2TiF6: Mn4+ phosphors were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR) and fluorescence spectrometer. As-prepared Na2TiF6: Mn4+ phosphors have hexagonal structures. Under 460 nm excitation, intense red emissions corresponding to 2Eg-4A2 transitions of Mn4+ are observed. The optimum doping mole fraction of Mn4+ is 4.77% and the quantum efficiency is 74% for this phosphor. The chromaticity coordinates of the Na2TiF6: Mn4+ phosphors are (0.681, 0.317). Decay curve of 2Eg state for as-prepared Na2TiF6: Mn4+ sample fits the second order exponential behavior, and the average lifetime is 3.148 ms. © 2015, SCIENCE PRESS. All right reserved.


Ye X.,Jiangxi University of Science and Technology | Ye X.,National Engineering Research Center for Ionic Rare Earth | Huang X.,Jiangxi University of Science and Technology | Hou D.,Jiangxi University of Science and Technology | And 6 more authors.
Physica B: Condensed Matter | Year: 2016

Bi3+, PO43- and BO33- doped Sc0.73Y0.2VO4:Eu0.073+ phosphors were synthesized by solid state reaction at 1200 °C. The structure, morphology and luminescence properties were investigated. The synthesized phosphors show narrow particle distribution with average size around 2 μm. Under 365 nm excitation, integrate emission intensity increases after doping with Bi3+, PO43- and BO33-. The optimal doping concentrations are 1%, 20%, 10% for Bi3+, PO43- and BO33-, respectively. The thermal stability is greatly improved, especially for BO33- doped sample, whose intensity is about 92% of its original intensity even at 200 °C. © 2016 Elsevier B.V. All rights reserved.


Lan Q.,Jiangxi University of Science and Technology | Lan Q.,National Engineering Research Center for Ionic Rare Earth | Huang Z.,Jiangxi University of Science and Technology | Xie F.,Jiangxi University of Science and Technology | And 2 more authors.
Zhongguo Xitu Xuebao/Journal of the Chinese Rare Earth Society | Year: 2015

Fe3+ has an intensive tendency of hydrolysis and is easy to form complexes with other ions, therefore the solvent extraction system containing Fe3+ is very complex. Using P204 or N235 to remove Fe3+ in rare earth extraction system, the organic phase with Fe3+ was stripped by hydrochloric acid, its stripping rate was low, and it had a deep influence on the ability of the extraction agents. In extraction system of P507-N235 hydrochloric acid, the Fe3+ in low acidity and the complex of FeCl4- formed in high acidity were extracted by p507 and N235, respectively, and the extraction rate could reach 99% and was hard to stripping. The removal of Fe3+ from the organic phase was investigated by using a complexing method consisting of oxalic acid and EDTA. The results showed that the stripping rate of Fe3+ was too low by using complexing method of oxalic acid, therefore the oxalic acid couldn't be used for the removal of Fe3+. At temperature of 25 ℃, stripping time of 14 min, feed phase proportion of 1∶1, the stripping rate of Fe3+ could reach 97.51% by using complexing method of EDTA, and the concentration of Fe3+ in organic phase could decrease to 0.002 g·L-1 after a four-stage cross-flow stripping. ©, 2015, Chinese Rare Earth Society. All right reserved.


Ye X.,Jiangxi University of Science and Technology | Ye X.,National Engineering Research Center for Ionic Rare Earth | Li Q.,Jiangxi University of Science and Technology | Wu D.,Jiangxi University of Science and Technology | And 2 more authors.
Kuei Suan Jen Hsueh Pao/Journal of the Chinese Ceramic Society | Year: 2015

As an important binary system of BaO-Lu2O3-SiO2 ternary system, BaO-SiO2 system was assessed via the thermodynamic calculation by the CALPHAD method based on experimental phase diagram and the relevant thermodynamic data. The Gibbs energy of high temperature solution was determined by an ionic two-sublattice model as (Ba2+)P(O2-,SiO4 4-, SiO2 0)Q. The calculated Gibbs energies of seven intermediate phases (i.e., Ba2SiO4, BaSi2O5, BaSiO3, Ba2Si3O8, Ba3Si5O13, Ba3SiO5, and Ba5Si8O21) are in reasonable agreement with the experimental data. In the SiO2-rich part, the optimized liquidus is in agreement with the experimental data and the calculated activities of SiO2 reproduce the experimental results within the error limits. The calculated activities of BaO differ from the experimental data in range of 50% (mole fraction) to 80% BaO, which may be caused by the experimental error. The liquid Gibbs energy of mixing was also calculated. The obtained self-consistent phase diagram and thermodynamic data can be used for single-phase phosphor research and related metallurgical systems. © 2015, Chinese Ceramic Society. All right reserved.


Ye X.-Y.,Jiangxi University of Science and Technology | Ye X.-Y.,National Engineering Research Center for Ionic Rare Earth | Li Q.,Jiangxi University of Science and Technology | Luo Y.,Jiangxi University of Science and Technology | And 2 more authors.
Materials Science Forum | Year: 2016

Only one intermediate compound Ba3Lu4O9 was identified at 1373, 1573 and 1773K in the BaO-Lu2O3system in present work.Based on the available experimental phase diagram and relevant thermodynamic data, BaO-Lu2O3 binary system was optimized and calculated by using CALPHAD method. The Gibbs free energy of high temperature solution was described by an ionic two-sublattice model as (Ba2+,Lu3+)P(O2-)Q. The calculated phase diagram, Gibbs energy of intermediate phaseBa3Lu4O9and Gibbs energy of mixing agree well with experimental results within error limits. The study will offer theoretical basis for further research of the phosphor matrix system of BaO-Lu2O3-SiO2, but also provide new idea for the phase diagram and thermodynamic research on related metallurgical slags, refractories, high-temperature superconductivity material systems. © 2016 Trans Tech Publications, Switzerland.


Wu D.,Jiangxi University of Science and Technology | Wu D.,National Engineering Research Center for Ionic Rare Earth | Ye X.,Jiangxi University of Science and Technology | Ye X.,National Engineering Research Center for Ionic Rare Earth | And 4 more authors.
Xiyou Jinshu/Chinese Journal of Rare Metals | Year: 2016

(Sc,Y)(V1-xBx)O4-x:Eu3+ (0≤x≤0.5) phosphors were synthesized by solid state reaction at 1200℃ for 3 h. Luminescence properties, structure and morphology of samples were investigated by fluorescence spectrophotometer, X-ray diffraction(XRD) and scanning electron microscope(SEM), respectively. The results showed the main emission peak was located at 620 nm under the UV excitation of 365 nm, which was due to 5D0→7F2 transitions of Eu3+. The luminescence intensity was 1.6 times relative to Sc0.73Y0.2VO4:Eu0.07 3+ phosphors when the x=0.1. There were a strong broad absorption band and a weak emission band with peak at 337 and 396 nm, respectively, when monitored at 620 nm. The samples doped with boron maintained the body-centered tetragonal structure of (Sc,Y)VO4:Eu3+ and the morphology essentially unchanged. The particles showed uniform distribution without visible aggregation. The internal quantum efficiency was 2 times higher when excited at 397 nm and the relative luminous intensity maintained 92% as the temperature was raised to 200℃. The samples showed high internal quantum efficiency and low thermal quenching, which was suitable for the UV-pumped white light emitting diode(LED) as red phosphor. © Editorial Office of Chinese Journal of Rare Metals. All right reserved.


Huang X.,Jiangxi University of Science and Technology | Li Q.,Jiangxi University of Science and Technology | Yang M.,Jiangxi University of Science and Technology | Luo Y.,Jiangxi University of Science and Technology | And 4 more authors.
Zhongguo Xitu Xuebao/Journal of the Chinese Rare Earth Society | Year: 2016

With the development of rare-earth materials, neodymium oxide with large particles has been widely used in high technology field. Study on the decomposition of neodymium oxalate to neodymium oxide benefits the preparation of neodymium oxide with excellent performance. The thermal decomposition of neodymium oxalate with large particles was investigated by TG/DTG/DTA in the present study. The activation energy E was calculated with Ozawa equation and Starink equation, as well as the reaction mechanism function deduced by Coats-Redfern integral method. At a heating rate of 10℃·min-1, neodymium oxalate lost water of hydration from room temperature to 397℃; anhydrous neodymium oxalate decomposed to Nd2O2CO3 between 397 and 584℃; Nd2O2CO3 decomposed to Nd2O3 in the temperature range between 584 and 770℃. The TG/DTG/DTA curves moved to the high-temperature sides with increasing the heating rate. The higher the heating rate, the higher corresponding temperature to reach the same mass loss rate was. With the maximum heating rate applied, the mass loss rate in the DTG curve was obviously higher, the peak area in the DTA curve was larger as well as the absolute value of enthalpy under the same temperature was bigger. From anhydrous neodymium oxalate to Nd2O2CO3, the decomposition energy was 130.10~187.8 kJ·mol-1. And the reaction was in accordance with the three-dimensional diffusion model. From Nd2O2CO3 to Nd2O3, the decomposition energy was 57.40~81.83 kJ·mol-1. © 2016, Editorial Office of Journal of the Chinese Society of Rare Earths. All right reserved.

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