A Single-Phase Phosphor NaLa9 (GeO4)6O2: Tm3+, Dy3+ for Near Ultraviolet-White LED and Field-Emission Display

Single-phase white-light-emitting phosphors NaLa9(1-x-y) (GeO4)(6)O-2: xTm(3+), yDy(3+) (NLGO: xTm(3+), yDy(3+)) have been synthesized by a traditional solid-state reaction method. The powder X-ray diffraction (XRD), photoluminescence (PL), PL excitation (PLE) spectra, fluorescence decay curves, chromaticity coordinates, correlated color temperature (CCT), and the cathodoluminescence (CL) properties of the obtained phosphors are measured and discussed in detail. It is discovered that the series samples could be color-tunable (from blue to yellow) by tuning the doping content of Dy3+ with a fixed Tm3+ content excited at 357 nm and white light (0.341, 0.324) could be obtained with the CCT of 5079 K. A NLGO: 0.01Tm(3+), 0.02Dy(3+) is studied carefully as representative. The main emissions of Tm3+ (453 nm, D-1(2)-F-3(4)) and Dy3+ (478 nm, F-4(9/2)-H-6(15/2;) 572 nm, F-4(9/2)-H-6(13/2)) make it emit white light with good thermal stability (67% of the initial till 523 K). The energy transfer from Tm3+ to Dy3+ is noticed and further research has been done to explain the enhancement of Dy3+ emission and the excellent thermal stability. It also keeps stable under continuous electron bombardment with high intensity. All of these indicate that it could be a suitable candidate for white-emitting phosphor applied for near ultraviolet-white light-emitting diode (NUV-WLED) and field-emission display (FED).