Electronic structure, energy transfer mechanism and thermal quenching behavior of K3YB6O12:Dy3+, Eu3+ phosphor

Rare-earth ions activated K3YB6O12:Dy3+, Eu3+ phosphors were successfully prepared by a high temperature solid state reaction. The electronic structure of K3YB6O12 was estimated by density functional theory. Under the excitation of ultraviolet light, K3YB6O12:Dy3+ presented two main emission bands with peaks at 487 nm and 576 rim, belonging to F-4(9/2) -> H-6(15/2) and F-4(9/2) -> H-6(13/2) transitions respectively. The variable emitting color was observed after co-doping with Eu3+ associated with the energy transfer between Dy3+ and Eu3+, which was confirmed by analyzing the photoluminescence spectra and the luminescence decay curves. Using the Dexter's theory and the Reisfeld's approximation, the energy transfer process from Dy3+ to Eu3+ can be explained by quadrupole-quadrupole interaction. Furthermore, the temperature dependent emission spectra of K3YB6O12: Dy3+, Eu3+ confirmed that the luminous intensity of 576 nm at 493 K was 78% of the initial value, suggesting the good emission thermal stability. It was worth noting that as the temperature increases, the emission intensity of Eu3+ hardly changed, which was different with that of Dy3+. Different thermal quenching phenomena of Dy3+ and Eu3+ were depicted in the coordinate graphics.