Molybdate based phosphors have efficient absorption in the ultraviolet (UV) region and can be used for UV-pumped light emitting. A series of NaGd0.5Tb0.5−xEux(MoO4)2 (0 ≤ x ≤ 0.5) multicolor tunable phosphors were prepared via a conventional solid-state reaction method. The as-prepared samples were well characterized by x-ray diffraction patterns, Fourier transform infrared spectroscopy, scanning electronic microscope, electron energy-dispersive spectroscopy, UV–vis diffused reflectance, photoluminescent spectra, decay curve and temperature-dependent photoluminescence spectra. The results indicate that the NaGd0.5Tb0.5−xEux(MoO4)2 (0 ≤ x ≤ 0.5) phosphors exhibit a good crystallinity and form a continuous solid solution with scheelite structure. Under UV excitation, NaGd0.5Tb0.5−xEux(MoO4)2 (0 ≤ x ≤ 0.5) phosphors exhibit characteristic emissions of Tb3+ (5D4 → 7FJ, J = 6, 5, 4, 3) and Eu3+ (5D0 → 7FJ, J = 0, 1, 2, 3, 4). The host NaGd(MoO4)2 has excellent energy transfer efficiency for rare earth ions, and the energy transfer from Tb3+ ions to Eu3+ ions is efficient, which can be confirmed by the decay curve. The energy transfer (ET) process between Tb3+ and Eu3+ was demonstrated to a reasonable type via a dipole–dipole interaction with ET efficiency of about nearly 95%. Moreover, the temperature-dependent luminescence properties indicated that the phosphors possessed good thermal stability. Interestingly, the luminescence color of NaGd0.5Tb0.5−xEux(MoO4)2 phosphors can be easily tuned from green to green-yellow, yellow, orange-yellow and ultimately to red by simply adjusting the related concentrations of Tb3+ and Eu3+ under a single wavelength excitation, which might have potential applications in the fields of as multi-color display and illumination.
NaGd0.5Tb0.5−xEux(MoO4)2 phosphors solid-state synthesis multicolor tunable luminescence properties energy transfer
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This work was supported by the National Science Foundation of China (NSFC, No. 51551202), the
Scientific Research Fund of Sichuan Provincial Education Department of Sichuan Province (Nos. 15ZA0363, 18ZA0408) and the Applied Basic Research Fund of Science and Technology Department of Sichuan Province (No. 2015JY0274).