Luminescence and energy transfer of a color tunable phosphor: Dy3+-, Tm3+-, and Eu3+-coactivated KSr4(BO3)3 for warm white UV LEDs

Abstract

A series of Dy 3+ -, Tm 3+ -, Eu 3+ -coactivated KSr 4 (BO 3 ) 3 phosphors were synthesized via a standard solidstate reaction under normal ambient air, and the emission colors could be tuned from blue to yellow and then to red, including almost all the white light region, through tuning the energy transfer. It was discovered that the energy is transferred from Tm 3+ to Dy 3+ by: directly observing overlap of the excitation spectrum of Dy 3+ and the emission spectrum of Tm 3+ ; the systematic relative decline and growth of emission bands of Tm 3+ and Dy 3+ , respectively; and faster decay times of the blue emissions from energy donors. The resonance-type energy transfer from Tm 3+ to Dy 3+ was demonstrated to be via the dipole-quadrupole mechanism and the critical distance of energy transfer was calculated to be 20.7 A. Rietveld refinements of the crystal structures of the products obtained from powder X-ray diffraction (XRD) elucidated a preferable occupancy in the crystal unit for the doped rare-earth cations, which well explained the formation of the Tm 3+ -Dy 3+ close pair. By utilizing the principle of energy transfer, we have demonstrated that with appropriate tuning of activator content, KSr 4 (BO 3 ) 3 :Dy 3+ ,Tm 3+ ,Eu 3+ phosphors exhibit great potential for use as single-component phosphors for warm white ultraviolet light-emitting diodes (UV LEDs).

Controlled synthesis of different multilayer architectures of GdBO3:Eu3+ phosphors and shape-dependent luminescence properties

“…12, the emission intensity increases with Eu 3+ substitution up to 0.25 and then decreases for additional concentrations of Eu 3+ . Given that luminescence quenching is caused by the energy transfer within the same rare earth ions, the critical distance between the doped ions can be calculated by the concentration quenching method using the following equation [8]:…”

“…And three-dimensional (3D) nano-/micro-materials have been explored for a new generation of advanced devices such as supercapacitors, fuel cells, and sensors [6]. Many methods have been used for the preparation of nano-/micro-structures, including hydrothermal synthesis [7], solid-state reaction [8], templatedirected synthesis [9], sol-gel method [10], catalytic growth [11], electrospinning process [12], sonochemistry-assisted microwave synthesis [13], co-precipitation [14], etc. Among all synthetic methods, the hydrothermal synthetic method has showed an extraordinary ability in the controllable fabrication of inorganic nano-/micro-structures.…”

White light emission materials of self‐assembled rare earth molybdates NaRe(MoO4)2 micro‐particles: the controllable synthesis, growth mechanism and luminescent properties

“…It was reported that Tm 3+ could be used in company with Dy 3+ to produce the white emissions [26,45]. This is because that the blue emissions ascribed to 1 figure 11A-left), the strong peak at 352 nm is ascribed to f-f transition of 3 H 6 → 1 D 2 , and the charge transfer band (CTB) cannot be observed at 250 ß300 nm, indicating that the energy transfer from MoO 4 2− to Tm 3+ ions does not take place.…”

Energy transfer mechanism and luminescence properties of color tunable LaPO4:Tm,Eu phosphor

“…Although the energy transfer behavior between Tm 3+ and Eu 3+ ions for LiYF 4 [12], KSr 4 (BO 3 ) 3 [13], zinc phosphate [14], and fluorozirconate [15] was presented, it was not discussed in-depth for phosphate phosphors. Therefore, in this study, the energy transfer mechanism, luminescence properties, crystallinity and color tunability of the LaPO 4 :Tm,Eu phosphor were investigated.…”