Structure and luminescent properties of Dy3+ activated NaLa9(SiO4)6O2 yellow-emitting phosphors for application in white LEDs
Résumé
A series of NaLa9-xDyx(SiO4)6O2 (NLSO:xDy, x = 0 – 0.3) apatite
phosphors were synthesized by solid-state reaction at 1100 °C. Their crystal
structure, morphology and particle size distribution, electronic structure, Raman
spectra, as well as concentration- and temperature-dependent luminescent
properties were investigated for the first time. The crystal structure is refined by the
Rietveld method. Undoped NLSO is hexagonal (space group P63/m – C2
6h) with
lattice constants a = b = 9.6917(3) Å and c = 7.1836(4) Å. Dy3+ ions substitute for the
La3+ ones in two types of sites. The first-principle calculations for undoped NLSO
reveal an indirect bandgap of 5.06 eV. The photoluminescence properties were
investigated in detail through the measurements of the emission spectra and
luminescence decay curves. The NLSO:0.2Dy phosphor exhibited the typical Dy3+
emission corresponding to 4F9/2 →6HJ transitions, among which the hypersensitive
electric-dipole transition 4F9/2→6H13/2 (571 nm) dominates in the spectrum leading to
yellow emission color with CIE chromaticity coordinates of (0.469, 0.495) and a
correlated color temperature of 3150 K. The concentration quenching mechanism
for Dy3+ ions was investigated. Excellent thermal stability was found for this new
apatite phosphor. The obtained results indicated that NLSO:xDy apatites are
promising as potential yellow emitting phosphors for applications in w-LEDs.
Domaines
Optique [physics.optics]
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