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Abstract: Tunable full color emissive LiSr3.99−x Dy0.01(BO3)3:xEu3+ (0≤x≤0.09) phosphors peaked at 481nm (blue), 574nm (yellow), 592nm (orange), and 617nm (red) were synthesized in air by high temperature solid-state reaction route. The as-synthesized phosphors were characterized by X-ray powder diffraction (XRD), photoluminescence excitation (PLE) and photoluminescence (PL) spectra. The PLE spectra in the range from 200 to 500nm include an Eu–O charge transfer band (CTB) and several 4f–4f transition peaks of Dy3+ and Eu3+, indicating its potential application in white light emitting diodes (LEDs). The effect of Eu3+ concentration on the emission intensity of LiSr3.99−x Dy0.01(BO3)3:xEu3+ phosphors was investigated in detail and the optical concentration is found to be x=0.005. The CIE chromaticity coordinates for LiSr3.99−x Dy0.01(BO3)3:xEu3+ phosphors are simulated. With an increase in Eu3+ ion concentration, the chromaticity color coordinates can be tuned efficiently from the border of greenish white region to its equal-energy white light point, and eventually to red region. All the results imply that the studied LiSr3.99−x Dy0.01(BO3)3:xEu3+ phosphors could be potentially used as white LEDs. [Copyright &y& Elsevier]

Abstract: The Ca3−x B2O6:xDy3+ (0.0≤ x ≤0.105) and Ca2.95−y Dy0.05B2O6:yLi+ (0≤ y ≤0.34) phosphors were synthesized at 1100°C in air by solid-state reaction route. The as-synthesized phosphors were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), photoluminescence excitation (PLE) and photoluminescence (PL) spectra. The PLE spectra show the excitation peaks from 300 to 400nm is due to the 4f–4f transitions of Dy3+. This mercury-free excitation is useful for solid state lighting and light-emitting diodes (LEDs). The emission of Dy3+ ions upon 350nm excitation is observed at 480nm (blue) due to the 4F9/2 → 6H15/2 transitions, 575nm (yellow) due to 4F9/2 → 6H13/2 transitions and a weak 660nm (red) due to 4F9/2 → 6H11/2 emissions, respectively. The optimal PL intensity of the Ca3−x B2O6:xDy3+ phosphors is found to be x =0.05. Moreover, the PL results from Ca2.95−y Dy0.05B2O6:yLi+ phosphors show that Dy3+ emissions can be enhanced with the increasing codopant Li+ content till y =0.22. By simulation of white light, the CIE of the investigated phosphors can be tuned by varying the content of Li+ ions, and the optimal CIE value (0.300, 0.298) is realized when the content of Li+ ions is y =0.22. All the results imply that the Ca2.95−y Dy0.05B2O6:yLi+ phosphors could be potentially used as white LEDs. [Copyright &y& Elsevier]