Energy transfer and luminescence properties of BaSr2Gd1-xMx(PO4)3 (M = Dy, Tm, Eu) phosphors for warm white UV LEDs

Novel single-phased white-light-emitting and color tunable BaSr2Gd(PO4)(3):Dy3+, Tm3+, Eu3+ phosphors were synthesized by solid-state reaction method and characterized with power X-ray diffraction (XRD), photo-luminescence excitation (PLE), photoluminescence (PL) and PL delay spectral measurement. Under the excitation of ultraviolet, dual energy transfer, namely, Dy3+ to Tm3+ and Dy3+ to Eu3+, exists in the system of BaSr2Gd(PO4)(3):Dy3+,Tm3+,Eu3+. The emission color of these phosphors can be accurately changed from greenish blue to blue via ET of Dy3+ to Tm3+ and from yellowish green to yellow via ET of Dy3+ to Eu3+. Under the excitation at 388 nm, BaSr2Gd0.91(PO4)(3):0.04Dy(3+),0.03Eu(3+),0.02 Tm3+ phosphor showed bright a white light with chromatic coordinate of (0.329,0.349). The as-prepared phosphors have a great potential as a credible candidate for near ultra-violet excited white light emitting phosphor.