The effect of Sm3+ co-doping on the luminescence properties of Ca2.85 Li0.15(PO4)1.85(SO4)0.15:Dy3+ white-emitting phosphors

A novel white emitting phosphate-based phosphor Ca3-x,Li-x(PO4)(2-x),(SO4)(x):Dy3+, Sm3+ with high emission intensity and lower correlated color temperature were successfully synthesized via the sol-gel method. The structures of these prepared phosphors matched well with standard Ca-3(PO4)(2). The Dy3+-doped Ca3-x,Li-x(PO4)(2-x),(SO4)(x) phosphors showed white luminescence via the combination of blue (487 nm) and yellow (578 nm) emissions, which were attributed to the F-4(9/2) -> H-6(15/2) and F-4(9/)2 -> H-6(13/2) electron transitions of Dy3+, respectively. The synthesized phosphor exhibited a significant enhancement in luminescence intensity at the optimum value of x = 0.15. With the incorporation of Sm3+, a warm white emission with lower correlated color temperature (4281 K) was achieved in Dy3+/Sm3+ co-doped samples. The obtained external quantum efficiency reached 21.7% in the optimized phosphor. The improved performance was strongly associated with red emission supplemented by Sm3+, and it demonstrated the existence of efficient energy transfer between the Dy3+ and Sm3+ ions (F-4(9/2) -> (4)G(7/2) and F-4(9/2) -> (4)G(5/2)). Overall, the investigation carried out by us has revealed that the luminescence properties of Ca-3(PO4)(2) phosphor can be significantly improved through Li+/S6+ partial substitution and Dy3+/Sm3+ co-doping. (C) 2019 Elsevier B.V. All rights reserved.