학술논문
Emission color tunability of dysprosium-activated YNbO4 –LuNbO4 -mixed phosphors
Document Type
Original Paper
Author
Source
Applied Physics A: Materials Science & Processing. 130(2)
Subject
Language
English
ISSN
0947-8396
1432-0630
1432-0630
Abstract
Herein, we demonstrate the photoluminescence properties of Dy3+ -activated YNbO4 , LuNbO4, and mixed Yx Lu1−x NbO4 :Dy3+ (x = 0.25, 0.5, 0.75) phosphors. For this purpose, five samples with a fixed Dy3+ concentration (2 mol%) were prepared by the solid-state reaction method. X-ray diffraction measurements showed that all phosphors crystallize in a monoclinic fergusonite-beta-(Y) structure with a C2/c space group. Scanning electron microscopy clearly shows that samples are composed of dense, well-developed micron-sized, cube-shaped grains with rounded edges. The photoluminescent emission spectra feature Dy3+ peaks at standard positions corresponding to transitions from the 4 F9/2 excited emitting level to the 6 HJ (J = 15/2; 13/2; 11/2 and 9/2) lower levels with two dominant emission bands placed in the blue (~ 479 nm, B) and yellow (~ 576 nm, Y) spectral region. It is observed that with Lu increase in the host lattice Y/B ratio decreases toward the desired ratio of unity to obtain white light. To evaluate the suitability of these phosphors for use in solid-state lighting, their photoluminescence emission was analyzed in detail by calculating CIE coordinates, correlated color temperature (CCT) and Delta u,v (DUV). It is shown that CIE chromaticity coordinates of all Dy3+ -activated Yx Lu1−x NbO4 samples (x = 0, 0.25, 0.5, 0.75, and 1) fall into the white portion of the diagram and that with the increase of Lu in the host lattice color becomes whiter. CCT values for all samples are in the cooler 4000–4500 K range with positive DUVs indicating that color points are placed above the black body curve. The average lifetime of 4 F9/2 level is calculated to be ~ 0.2 ms for all Dy3+ -activated Yx Lu1−x NbO4 samples, indicating that there is no influence of the Y-to-Lu ratio in the host niobate material on the luminescence kinetics.