Tunable multicolor luminescence and energy transfer mechanism in Eu3+/Dy3+ co-doped Ca2Sb2O7 phosphor under UV excitation

A series of Ca(2-x-y)Sb2O7:xDy(3+),yEu(3+) phosphors with tunable multicolor luminescence were synthesized via solid-state reaction method. The XRD, EDX and HR-TEM analysis confirmed the phase purity and the crystallinity of the samples. Under ultraviolet (UV) excitation, Ca(2-x-y)Sb2O7:xDy(3+),yEu(3+) phosphors exhibit characteristic emission bands of both Dy3+ and Eu3+ ions, along with an intense blue emission band of the host. The emission peaks at 575 and 660 nm correspond to F-4(9)/2 -> H-6(13/2) and F-4(9)/2 -> H-6(11/2) transitions of Dy3+ ions, and the peaks at 528 and 612 nm originate from D-5(1)-> F-7(1) and D-5(0) -> F-7(2) transitions of Eu3+ ions, respectively. There exists efficient energy (ET) transfer from host to Eu3+/Dy3+ ions, as well as from Dy3+ to Eu3+ ions. The decay lifetime of host and Eu3+/Dy3+ emissions were calculated to be in the microsecond range. By properly modulating the concentration of Eu3+/Dy3+ ions, the CIE chromaticity coordinates of the samples vary from (0.144, 0.097) to (0.446, 0.312). Hence, multicolor emission which can be tuned from blue to bluish-white and eventually to reddish-white can be obtained in the warm CCT region. The results indicate that Ca2Sb2O7:Dy3+,Eu3+ phosphor could be a promising candidate for UV excited WLEDs and multicolor displays.