Effects of Ti4+- and W6+-substitution on photoluminescence properties of Sr2GdSbO6:Mn4+ phosphor for plant cultivation

Abstract A novel double perovskite Ti4+ and W6+ modified Sr2GdSbO6 (SGSO):Mn4+ far-red phosphor was prepared by traditional solid state reaction method. The samples were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence spectra (PL), decay life, temperature-dependent emission spectra and internal quantum efficiency (IQE). Due to the 2E→4A2 transition of Mn4+ ions, the emission band centered at 667 nm was observed in the range of 600–780 nm, which matched the absorption spectra required for plant growth. The excitation spectra consist of four excitation bands, peaking at 276, 305, 358 and 506 nm in the range of 220–600 nm, respectively, which indicates that SGSO:Mn4+ phosphors can be excited by ultraviolet, near-ultraviolet and blue light emitting diode (LED) chips. The optimum doping concentration of Mn4+ is determined to 0.4 mol% and the concentration quenching mechanism is the dipole-quadrupole interaction of Mn4+ activator. The effect of co-doping Ti4+ and W6+ ions on the luminescent properties of SGSO:Mn4+ was studied. The PL intensity of SGSO:0.004Mn4+, 0.004Ti4+ and SGSO:0.004Mn4+, 0.004 W6+ are 1.65 and 2.07 times than that of SGSO:0.004Mn4+ phosphor. Impressively, all samples possess excellent thermal stability (I423K/I298K>70%). The results illustrate that Ti4+ and W6+ can significantly improve the luminescent properties and thermal stability of SGSO:Mn4+. Finally, a kind of LED device was fabricated by combining 365 nm ultraviolet LED chip with far-red light emitting SGSO:0.004Mn4+, 0.004 W6+ phosphors and BaMgAl10O17:Eu2+ blue phosphor. Because the emission band of SGSO:0.004Mn4+, 0.004 W6+ matches well with the absorption band of plant pigment PR, under the excitation of near ultraviolet (UV) to blue light, SGSO:0.004Mn4+, 0.004 W6+ phosphors have potential application prospects in indoor plant cultivation.