Key Words:Density functional theory;Activation energy - Cadmium compounds - Emission spectroscopy - Europium - Light emission - Luminescence - Phosphors - Photoluminescence - Quenching - Solid state reactions - X ray powder diffraction;Activation energies (Ea) - Blue-green emissions - Concentration quenching - Luminescent property - Periodic density functional theory - Solid state reaction method - Structural refinement - Temperature dependent
Abstract:The luminescent properties of Eu²⁺ions are strongly influenced by their occupied position in host. In this paper, the luminescent properties of Eu²⁺in BaCdP<inf>2</inf>O<inf>7</inf>: Eu²⁺phosphor were studied from experimental and theoretical aspects. BaCdP<inf>2</inf>O<inf>7</inf>: xEu²⁺(0.01 &le; x &le; 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 BaCdP<inf>2</inf>O<inf>7</inf>show that there are a 9-coordinated Ba²⁺lattice site and a 6-coordinated Cd²⁺lattice site in BaCdP<inf>2</inf>O<inf>7</inf>compound. The emission spectrum can be fitted well by two Gaussian peaks at 436 nm and 487 nm, implying that both Ba²⁺and Cd²⁺lattice sites may be occupied by Eu²⁺ions. The calculation using the empirical Van Uitert equation further qualitatively reveals that Eu²⁺occupies both Ba²⁺and Cd²⁺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<inf>a</inf>) calculations. Namely, our simulations and experiments simultaneously provide the proof that Eu²⁺can replace both Ba²⁺and Cd²⁺to be a blue-green phosphor. In addition, concentration quenching mechanism, temperature-dependent luminescence and CIE chromaticity coordinate of the BaCdP<inf>2</inf>O<inf>7</inf>: Eu²⁺phosphors were also investigated in this work. All the results indicate that BaCdP<inf>2</inf>O<inf>7</inf>: Eu²⁺phosphor is a potential blue-green phosphor for near ultraviolet-based white-emitting diodes (WLEDs). &copy; 2017 Elsevier Ltd
Volume:149
Issue:
Translation or Not:no