Luminescent properties of Eu2+ in BaCdP2O7: Eu2+ phosphor: Experimental and theoretical analysis. (February 2018) - Wu, Zhan-Chao
Abstract: The luminescent properties of Eu 2+ ions are strongly influenced by their occupied position in host. In this paper, the luminescent properties of Eu 2+ in BaCdP2 O7 : Eu 2+ phosphor were studied from experimental and theoretical aspects. BaCdP2 O7 : x Eu 2+ (0.01 ≤ x ≤ 0.06) phosphors, synthesized by a solid-state reaction method under CO atmosphere, exhibited a strong asymmetric blue-green emission at 445 nm. X-ray powder diffraction (XRD) characterization and the Rietveld structural refinements for BaCdP2 O7 show that there are a 9-coordinated Ba 2+ lattice site and a 6-coordinated Cd 2+ lattice site in BaCdP2 O7 compound. The emission spectrum can be fitted well by two Gaussian peaks at 436 nm and 487 nm, implying that both Ba 2+ and Cd 2+ lattice sites may be occupied by Eu 2+ ions. The calculation using the empirical Van Uitert equation further qualitatively reveals that Eu 2+ occupies both Ba 2+ and Cd 2+ sites, and then emits blue (436 nm) and green (487 nm) light, respectively. Furthermore, above results are also confirmed by the results of the periodic density-functional theory (DFT) and activation energy ( E a ) calculations. Namely, our simulations and experiments simultaneously provide the proof that Eu 2+ can replace both Ba 2+ and Cd 2+ to be a blue-green phosphor. In addition, concentration quenching mechanism, temperature-dependent luminescence and CIE chromaticity coordinate of the BaCdP2 O7 : Eu 2+ phosphors were also investigated in this work. All the results indicate that BaCdP2 O7 : Eu 2+ phosphor is a potential blue-green phosphor for near ultraviolet-based white-emitting diodes (WLEDs). Graphical abstract: Highlights: The occupied position of Eu 2+ in BaCdP2 O7 lattice was systematically studied. The results of simulations and experiments indicate that Eu 2+ can replace both Ba 2+ and Cd 2+ . Quadrupole-quadrupole interaction is the concentration quenching mechanism of Eu 2+ ions. The BaCdP2 O7 : Eu 2+ phosphor shows good thermal stability.