ABSTRACT
Single-phase CaSr2(PO4)2:Sm3+,Li+ phosphors were prepared via a high-temperature solid-state method under air. The powder X-ray diffraction patterns, scanning electron microscopy images, photoluminescence spectra, and concentration-dependent emission spectra were measured to characterize the as-prepared phosphors and luminescence decay curves. The results showed that the CaSr2(PO4)2:Sm3+,Li+ phosphors exhibited red luminescence, and the emission spectra of the phosphors consisted of four sharp peaks at around 565, 601 (the strongest one), 647 and 707 nm. The optimum doping concentration of Sm3+ ions was 0.09 (mol concentration), and the mechanism of energy transfer among Sm3+ ions was defined to be quadrupole-quadrupole (q-q) interactions using Dexter's theory. The Blasse concentration quenching method was used to determine the critical distance R c for energy transfer among Sm3+ as 10.99 Å. The results indicate that the as-prepared phosphors have good thermal stability with an activation energy of 0.773 eV via temperature-dependent emission spectra. Therefore, CaSr2-2x (PO4)2:xSm3+,xLi+ materials can be used as red-emitting phosphors for UV-pumped white-light emitting diodes.
ABSTRACT
In recent years, compounds with a cryolite structure have become excellent hosts for luminescent materials. In this paper, Tb3+ doped and Tb3+/Eu3+ co-doped K3LuF6 phosphors were prepared via a high temperature solid phase sintering method. The XRD, SEM, as well as photoluminescence excitation (PLE) and emission (PL) spectra were measured to investigate the structure and luminescence properties of the as-prepared samples. In the Tb3+/Eu3+ co-doped K3LuF6 samples, both characteristic emission spectra of Tb3+ and Eu3+ could be observed and the emission color of the K3LuF6:0.12Tb3+,xEu3+ phosphors could be adjusted from green to yellowish pink and the corresponding CIE values could be regulated from (0.2781, 0.5407) in the green area to (0.4331, 0.3556) in the yellowish pink area by controlling the concentration ratio of Eu3+/Tb3+. In addition, the energy transfer mechanism in Tb3+/Eu3+ co-doped K3LuF6 was calculated to be a quadrupole-quadrupole interaction from Tb3+ to Eu3+ based on the Dexter's equation.
ABSTRACT
The Ba2La2.85-x Tb0.15Eu x (SiO4)3F (BLSOF:0.15Tb3+, xEu3+) multicolor phosphors with apatite structure were synthesized via the solid-state pathway. The crystal structure and luminescence properties of the phosphors were investigated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), Rietveld refinement, photoluminescence excitation (PLE) and photoluminescence (PL). The luminescence performance of the phosphor was optimum when the concentration of Tb3+ was set to be 0.15 mol and the concentration of Eu3+ was set to be 0.22 mol. Under the accurate excitation of 373 nm near ultraviolet (n-UV) light, the emitting color of the phosphors can be tuned from green to red with increasing Eu3+/Tb3+ ratio. It was further proved that the quadrupole-quadrupole (q-q) interaction is responsible for the energy transfer (ET) in the BLSOF:0.15Tb3+, 0.22Eu3+ phosphor. Owing to the excellent thermal quenching luminescence property, the BLSOF:0.15Tb3+, xEu3+ phosphor can be applied in n-UV white light emitting diodes (w-LEDs) and serve as the warm part of warm white light.
ABSTRACT
In this study, we investigated the structure, luminescence properties and morphology of La6Ba4(SiO4)6F2:Dy3+ in detail using X-ray diffraction (XRD), photoluminescence spectroscopy, scanning electron microscopy (SEM) and decay kinetics measurements. The results indicate that La6Ba4(SiO4)6F2:Dy3+ was well crystallized, and its structure is of apatite-type and belongs to the hexagonal system. The prepared samples exhibit two intense characteristic bands in the blue (484 nm) and yellow (579 nm) spectral ranges corresponding to the Dy3+ transitions 4F9/2 â 6H15/2 and 4F9/2 â 6H13/2, respectively. These dominant photoluminescence bands are accompanied by a weak red band (670 nm) due to the 4F9/2 â 6H11/2 transition. The emission color of La6Ba4(SiO4)6F2:Dy3+ phosphors are found to fall in the white light region. The Dy3+ optimal dopant concentration in the La6Ba4(SiO4)6F2 host was found to be 0.12 (mol). In addition, the phosphors have high thermal stability. Hence, La6Ba4(SiO4)6F2:Dy3+ may have an application in white light-emitting diodes.
