Color Tuning from Greenish-Yellow to Orange-Red in Thermal-Stable KBaY(MoO4)3:Dy3+, Eu3+ Phosphors via Energy Transfer for UV W-LEDs

In this report, a series of tunable-emitting KBaY(MoO4)(3):Dy3+, Eu3+ (KBYMO:Dy3+, Eu3+) phosphors were synthesized via a Pechini-type sol-gel reaction approach. XRD and Rietveld refinement results confirm the pure phase of as-prepared materials. Upon 351 nm excitation, the optimal sample KBYMO:0.05Dy(3+) shows its two main characteristic emission bands around 488 and 573 nm, which correspond to Dy3+ transitions F-4(9/2) -> H-6(15/2) and F-4(9/2) -> H-6(13/2), respectively, in addition to a weak band around 660 nm originating from Dy3+ F-4(9/2) -> H-6(11/2) transition. In the excitation spectrum monitored at 573 nm, it is worth noting that there are two excitation peaks at 365 and 453 nm, matching with commercial LED chips. With the addition of Eu3+ into KBYMO:0.05Dy(3+), the energy transfer from Dy3+ to Eu3+ is elucidated, resulting in the tunable emission color from greenish-yellow to orange-red with increasing Eu3+ content upon a 365 nm UV lamp excitation, which can be proved by analyzing the profiles of the excitation and emission spectra of Dr(3+), Eu3+ codoped KBYMO and the decay times of Dy3+. The energy-transfer mechanism is determined to be a quadrupole-quadrupole interaction according to Dexter theory and Reisfield's approximation. Moreover, the temperature- dependent luminescence property of representative KBYMO:0.05Dy(3+), 0.10Eu(3+) is evaluated, which presents an emission intensity maintenance of 82.8% at 423 K relative to room temperature 298 K, showing its good performance. These results indicate that the as-prepared KBYMO:Dy3+, Eu3+ phosphors may be a candidate component applied in UV w-LEDs.