Sol–gel synthesis and luminescence property of Sr₄Al₂O₇:Re3⁺,R⁺ (Re = Eu and Dy; R = Li, Na and K) phosphors for white LEDs

Abstract

Sr Al O :Eu and Sr Al O :Dy phosphors with alkali metal substitution were prepared using a sol-gel method. The effects of a charge compensator R on the structure and luminescence of Sr Al O :Re ,R (Re = Eu and Dy; R = Li, Na and K) phosphors were investigated in detail. Upon heating to 1400°C, the structure of the prepared samples was that of the standard phase of Sr Al O . Under ultraviolet excitation, all Sr Al O :Eu ,R samples exhibited several narrow emission peaks ranging from 550 to 700 nm due to the 4f → 4f transition of Eu ions. All Sr Al O :Dy ,R phosphors showed two emission peaks at 492 and 582 nm, due to the F → H and F → H transitions of Dy ions, respectively. The luminescence intensity of Sr Al O :Re ,R (Re = Eu and Dy; R = Li, Na and K) phosphors improved markedly upon the addition of charge compensators, promoting their application in white light-emitting diodes with a near-ultraviolet chip.

Enhanced Red Emission of Na5Lu9F32: Eu3+ Single Crystal by Introducing of GdF3

“…All absorption lines are well corresponding to the electronic configuration of 4f (Eu 3 + ) and charge transfer band (CTB). [14,15] The 394 nm absorption band is assigned to the transition of Eu 3 + : 7 F 0 ! 5 L 6 , while the absorption band in the range of 200-275 nm is triggered by Eu 3 + -F À charge transfer.…”