The luminescence properties of Eu2+ doped Na2CaMg(PO4)2 phosphor

Applied Physics A (Impact Factor: 1.7). 06/2010; 99(4):859-863. DOI: 10.1007/s00339-010-5614-3


The blue-emitting phosphors of Eu2+-doped Na2CaMg(PO4)2 were prepared by high-temperature solid-state reaction. The crystal phase formation was confirmed by X-ray powder diffraction
measurement. The luminescence properties were investigated by photoluminescence excitation and emission spectra. The phosphor
exhibited the blue luminescence due to the 4f65d1→4f7 transition of Eu2+ ions under the excitation of near UV light. The influence of temperature on the luminescence intensities and decay lifetimes
of Eu2+ was investigated. An unusual increase of the decay lifetimes of the 4f65d emission of Eu2+ ion is observed in Na2CaMg(PO4)2 from 10 K to room temperature. The thermal stability of the luminescence of Eu2+-doped Na2CaMg(PO4)2 was discussed.

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    ABSTRACT: Mn2+-doped phosphates Na2CaMg1−xMnx(PO4)2 (x = 0.05–1.0) were prepared by conventional solid-state reaction. X-ray powder diffraction (XRD), the emission and excitation spectra, and decay measurements were employed to characterize the synthesized phosphors. The XRD patterns show that Na2CaMg1−xMnx(PO4)2 (x = 0.05–0.3) forms the single low temperature monoclinic phase α-Na2CaMg(PO4)2 with the crystal group of P21/c (No.14). The heavily Mn2+-doped Na2CaMg1−xMnx(PO4)2 (x = 0.6–1.0) crystallizes in the single high-temperature trigonal phase of β-Na2CaMg(PO4)2 with space-groupPm1 (No. 164). The members with x = 0.3–0.5 form a series of solid solutions containing two distinct phases, α- and β-Na2CaMg(PO4)2. The dependence of luminescence spectra on the Mn2+-doping concentration in Na2CaMg1−xMnx(PO4)2 (x = 0.05–1.0) was investigated. The great red-shift of Mn2+ emission with increasing Mn2+-concentration in Na2CaMg(PO4)2 were observed. The results are discussed in relation with the detailed crystal structure and the spectral analyses. The CIE coordinates and the luminescence decay (lifetimes) of Mn2+ ions were discussed in order to further investigate the potential applications.
    No preview · Article · Oct 2011 · Journal of Materials Chemistry
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    ABSTRACT: Rietveld refinements of X-ray powder diffraction data and vibrational spectroscopy have confirmed the crystal structure of Na2MMgP2O8 (M: Ba, Sr, Ca) prepared by a standard solid state reaction. They have glaserite-type layered structure. Na2MMgP2O8 has a trigonal P3̄ form for M=Ba, and monoclinic P21/c forms for M=Sr and Ca. The observed structural transition is analogous to the corresponding layered orthosilicate M3MgSi2O8.Eu2+-doped Na2MMgP2O8 exhibits an intense blue to violet emission under ultraviolet excitation, based on 5d–4f electron transition of Eu2+ ions. The emission character is very sensitive to the structural transition induced by M2+ and the subsequent site symmetry changes.
    No preview · Article · Dec 2011 · Journal of Solid State Chemistry
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    ABSTRACT: A new phosphate Na2SrMg(PO4)2 has been synthesized and investigated by X-ray diffraction, DTA, 31P NMR spectroscopy and photoluminescence measurements. This compound crystallizes in the space group P21/a of the monoclinic system with the cell parameters: a = 9.158(1) Å, b = 5.267(1) Å, c = 13.498 (1) Å, β = 90.01(1)° and four formula units per cell. Its structure is closely related to that of the mineral glaserite K3Na(SO4)2 and thus it can be described by the general formula XY2M(TO4)2. The X, Y, M and T sites are fully occupied by Sr2+, Na+, Mg2+ and P5+ cations, respectively. The anionic framework is consisted by the stacking along the [001] direction of two kinds of alternating [MgP2O84−]∞ mixed layers parallel to the (a, b) plane and resulting from a corner-sharing between MgO6 octahedra and PO4 tetrahedra. The Sr2+ cations are located within the interlayer space, while those Na+ are found in large cavities bounded to the layers. The DTA analysis showed a congruent melting of this compound at 1374 K. The 31P NMR spectroscopy confirmed the presence of two distinct phosphors sites in the structure. Optical studies were performed on the Na2SrMg(PO4)2 compound doped with Eu3+ and Eu2+. The trivalent europium was used as a local probe, replacing strontium and sodium, what gives complementary and consistent results to the crystallographic analyses. The divalent europium was used to analyze preliminary the potentiality for this compound to be integrated as phosphor in Light Emitting Diode (LED).
    No preview · Article · Nov 2012 · Materials Chemistry and Physics
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