title: Emerging cool white light emission from Dy(3+) doped single phase alkaline earth niobate phosphors for indoor lighting applications.
abstract: Single-phase cool white-light emitting BaNb2O6:Dy(3+) phosphors have been synthesized via a conventional solid-state reaction method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) observations and spectrofluorophotometric measurements. XRD and Rietveld structural refinement studies confirm that all the samples exhibit pure orthorhombic structure [space group -C2221(20)]. SEM observations reveal the dense particle packaging with irregular morphology in a micron range. The as-prepared phosphors exhibit blue (482 nm) and yellow (574 nm) emissions under 349, 364, 386 and 399 nm excitations corresponding to (4)F9/2→(6)HJ (J = 15/2, 13/2) transitions of Dy(3+) ions. The energy transfer mechanism between Dy(3+) ions has been studied in detail and the luminescence decay lifetime for the (4)F9/2 level was found to be around 146.07 μs for the optimized phosphor composition. The calculated Commission Internationale de L'Eclairage (CIE) chromaticity coordinates for the optimized phosphor are (x = 0.322, y = 0.339), which are close to the National Television Standard Committee (NTSC) (x = 0.310, y = 0.316) coordinates. The values of CIE chromaticity coordinates and correlated color temperature (CCT) of 5907 K endorse cool white-light emission from the phosphor. The study reveals that BaNb2O6:Dy(3+) phosphor could be a potential candidate for near ultra-violet (NUV) excited white-LED applications.
authors.affiliation: Luminescent Materials Research Lab, Department of Applied Physics, Delhi Technological University, Delhi 110 042, India. jayaphysics@yahoo.com.
authors.forename: Amit K
authors.initials: AK
authors.lastname: Vishwakarma
authors.forename: Kaushal
authors.initials: K
authors.lastname: Jha
authors.forename: M
authors.initials: M
authors.lastname: Jayasimhadri
authors.forename: B
authors.initials: B
authors.lastname: Sivaiah
authors.forename: Bhasker
authors.initials: B
authors.lastname: Gahtori
authors.forename: D
authors.initials: D
authors.lastname: Haranath