Structure, energy transfer, and luminescence properties of NaLaMgWO 6 : Tb 3+ ,Eu 3+ phosphors for solid-state lighting

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Structure, energy transfer, and luminescence properties of ­NaLaMgWO6: ­Tb3+,Eu3+ phosphors for solid‑state lighting Guifang Li1   · Yu Wang1 · Yunge Wei1 · Xiaohui Wang1 Received: 10 September 2019 / Accepted: 16 January 2020 / Published online: 3 February 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020

Abstract Novel ­NaLaMgWO6:Tb3+,Eu3+ phosphors with tunable color emissions were prepared by a solid-state reaction. The crystal structure, composition, and luminescent properties of the obtained phosphors were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), and fluorescence spectrophotometer. The results reveal that N ­ aLaMgWO6 crystal­ u3+ single-doped phosphors show the lizes in a monoclinic double perovskite structure with C2/m space group. T ­ b3+ and E intense green and red emissions at 545 and 617 nm, corresponding to the 5D4 → 7F5 transition of ­Tb3+ and the 5D0 → 7F2 transition of ­Eu3+, respectively, while for T ­ b3+ and ­Eu3+ co-doped phosphors, a tunable emission color from green to red is 3+ obtained by variation of the ratio of ­Eu to ­Tb3+. The emission spectra and luminescence decay lifetimes verify the occurrence of energy transfer from T ­ b3+ to E ­ u3+ in N ­ aLaMgWO6: ­Tb3+, ­Eu3+ phosphor, and the energy transfer mechanism is dominated by the dipole–quadrupole interaction. Furthermore, the thermal stability of ­NaLaMgWO6:Tb3+, ­Eu3+ phosphor was discussed from 305 to 515 K. The results exhibit the phosphors possess excellent thermal stability, and the activation energy is calculated to be 0.302 eV.

1 Introduction Phosphor-converted white light emitting diodes (pc-LEDs) have been used in numerous fields, such as indoor and outdoor lighting, screen display, and safety warning, because of their environmental friendliness, long lifetime, high brightness, and reliability. Nowadays, the most common way to achieve white LEDs is to combine a blue LED chip (InGaN) with yellow-emitting phosphors ­(Y3Al5O12:Ce3+) [1, 2]. However, the deficiency of red-emitting component leads to poor color-rendering index and low stability of color temperature that restrict its applications. To circumvent these drawbacks, ultraviolet (UV) LED chips can be combined with tricolor (blue, green, and red) phosphors to obtain high-quality white LEDs. Nevertheless, they still suffer from some problems, such as low luminous efficiency and poor color stability because of the strong reabsorption of blue light by the red and green phosphors. Using single-phase phosphors with tunable emission can effectively avoid the above problems [3, 4]. Therefore, it is important and urgent * Guifang Li [email protected] 1



School of Advanced Materials and Nano Technology, Xidian University, Xi’an 710071, China

to explore single-phase tunable color phosphors with high luminescent efficiency under UV. On the basis of energy transfer from the sensitizer to the activator, the combination of multiple activator ions in single-phase host is assumed to be a feasible method to realize tun

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