The luminescence properties of CaZnOS: Bi3+, Sm3+, Li+ phosphors with tunable emissions and energy transfer for white emission

Abstract A series of CaZnOS: Bi 3+ , Sm 3+ , Li + phosphors are prepared by solid-state reaction method at high temperature in H 2 /N 2 atmosphere. The site occupation of activators and luminescence properties, as well as energy transfer mechanism were investigated in detail. The Ca 2+ positions are occupied by the Bi 3+ and Sm 3+ ions according to the XRD Rietveld refinement. Under the excitation at 366 nm, the CaZnOS: Bi 3+ , Sm 3+ , Li + phosphors show an intense broad emitting band peaking at 490 nm owing to the 3 P 1,0 → 1 S 0 transition of Bi 3+ , and four red emitting bands within the wavelength range of 550–750 nm which can be assigned to the 4 G 5/2 → 6 H J ( J  = 5/2, 7/2, 9/2 and 11/2) transition of Sm 3+ . The emission color changes from blue-green to orange-red, and the decay time drastically decreased with increasing Sm 3+ concentration, attributing to the energy transfer from Bi 3+ to Sm 3+ . In addition, the co-doped phosphor exhibits better thermal quenching property compared with single activated samples. A cold-white LED was fabricated by using single CaZnOS: Bi 3+ , Sm 3+ , Li + as the wavelength conversion phosphor combined with a UV LED chip, and the obtained LED exhibits the high Ra (88.9) and CCT (8836 K).