Luminescence Properties Of Multi-molybdate Red Phosphors For White Leds

In the 21st, white light-emitting diodes (WLEDs), as the promising solid-state lighting sources to replace the conventional incandescent and fluorescent lamps, have attracted much attention due to their high reliability, long lifetime, low energy consumption and environment-friendly characteristics. The most effective approach to obtain WLED is phosphor - converted. However, the current red-emitting phosphor used for WLED reveals a rather low red emission under near-UV light excitation. Hence, it is necessary to search new red phosphors that can be efficiently excited around near-UV light.In this paper, a series of red phosphors containing (Na,M)₅Eu(MoO₄)₄ [M = Li, K], Na₅Eu(MoO₄)_4-xM_y [M = (PO₄)^3-,(SO₄)^2-,(ClO₃)^-], Na₅Eu(MoO₄)_4-x(PO₄)_xLi_x, Na₅Eu(MoO₄)_4-x(ClO₃)_xCl_x and LiGd_1-xEu_x(MoO₄)₂, LiGd_0.6-xY_xEu_0.4(MoO₄)₂ were prepared by conventional solid-state reaction. The influence of reaction conditions, doping concentration on the system structure and luminescence properties was investigated.In order to analyze the effects of different doped ions and different substrates on the characteristics of system, XRD, SEM, excitation and emission spectra were carried out. XRD proves that the different doping Na₅Eu(MoO₄)₄ system samples belong to a tetragonal scheelite-like structure. The different doping LiGd(MoO₄)₂ system samples pertain to a tetragonal scheelite-structure. Samples of the two systems are space group I41/a. SEM photographs show that the effective doping can improve the crystallization effect and modify the morphology of the samples. With near-UV 395 nm light, the excitation and emission spectra of all phosphors exhibit superior red emission to the commercial red phosphor Y2O2S: Eu³⁺.In this work, the influence of reaction conditions, doping concentration on the system structure and luminescence properties of Eu³⁺ doped molybdates were investigated, which expected to give the valuable reference to explore novel red phosphors for WLED.