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Following the rapid growth of lightning technology, the development of red-emitting phosphors is effective for improving color temperature and color rendering index for w-LEDs devices. Herein, a single phased garnet phosphor with cation and polyhedron substitution modification was firstly prepared. For Mg 3 Gd 2 Ge 3 O 12 : Bi3+, Eu3+, the intensity has been remarkably improved by about 16% compared to the one without Bi3+ sensitization. The energy transfer mechanism is identified in this work. Based on cation and polyhedron substitution strategies, novel phosphors with different compositions were obtained and further modified the PL properties. With Lu3+ substitution, the bond lengths between Bi3+ ion and anion ligands are decreased and the site symmetry has been strengthened, which leads to a 21 nm blue shift when Lu3+ totally replaced Gd3+ ions. In addition, Lu3+ and [SiO 4 ] substitution strategies both effectively increased symmetric rigid structure, which leads to a significant improvement in thermal stability, indicating the samples own great potential in optical applications This work provides a new insight to synthesis red-emitting phosphors for warm white-LEDs. [ABSTRACT FROM AUTHOR]

Rare earth doped luminescent sensing materials as non-contact thermometers have attracted extensive research interests due to their wide applications in areas like military, medical care, aerospace, etc. How to expand the working temperature range and improve the sensitivity has become the focus. In this work, we synthesized a series of apatite-structured luminescent temperature sensors M 2 La 7.9 Ce 0.1 (SiO 4) 6 O 2 (M = Ca, Sr, Ba) via isomorphic substitution. By monitoring the differential changes of emission intensities from Ce3+ at the 7-coordinate and 9-coordinate site respectively when temperature varies, the real-time temperature can be determined. These materials were proven to possess the maximum absolute sensitivity up to 0.825 × 10−3 K−1, 2.63 × 10−3 K−1 and 4.33 × 10−3 K−1, respectively. Meanwhile interesting regular patterns were observed for their temperature sensitivities with the substitution of Ca, Sr and Ba. Furthermore, through studying the temperature sensitivity of Ba 2 La 8 (SiO 4) 6 O 2 : x Ce3+ samples with different concentrations, it was found that when the Ce3+ content was at the optimal doping concentration of 0.7, the absolute sensitivity of the sample reached 14.64 × 10−3 K−1 at 573 K. This finding has opened up a new avenue for designing fluorescent temperature sensors. Synopsis: In this work, Ce3+ were doped into a series of phosphor-structured matrices containing two cationic sites (7-coordinated Ce1 and 9-coordinated Ce2 sites) via the solid-state high-temperature method. Due to the different temperature dependencies of luminescence intensities between the two Ce3+ sites, their intensity ratio could be used for temperature calibration. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract A set of Eu3+, Dy3+ and Tb3+ doped novel scheelite-type LiCaGd(WO 4) 3 (LCGW)-based phosphors was prepared via a conventional solid-state reaction method. The X-ray diffraction (XRD), transmission electron microscopy (TEM) analysis, characteristics of luminescence, PL thermostability, decay lifetimes, as well as CIE coordination were investigated to characterize the as-prepared samples in detail. The XRD analysis indicated that the Eu3+, Dy3+ and Tb3+ ions were incorporated into the LCGW host lattice. Under the ultraviolet radiation, the characteristic emission lines of Eu3+ (5D 0 –7F 2), Dy3+ (4F 9/2 –6H 13/2) and Tb3+ (5D 4 –7F 5) ions were observed. The Eu3+ and Tb3+ single-doped LCGW fluorescent powders showed bright red and green emissions, respectively, without concentration quenching. As well as the Dy3+ doped LCGW phosphors radiate a strong yellow light at optimal Dy3+ concentration 0.08 mol. The efficient energy transfer phenomenon was observed for the Eu3+/Dy3+ and Tb3+/Dy3+ ions. The emission color of the LCGW: x Tb3+/0.08Dy3+ samples was tuned from yellow (0.4074, 0.4727) to green (0.3604, 0.5521) via adjusting the Tb3+ concentration. The emission color of LCGW: y Eu3+/0.08Dy3+ can be tuned from yellow (0.491, 0.3856) to red (0.5694, 0.3512) by variation of the Eu3+/Dy3+ ratio. Additionally, the thermal stability of the luminescence in the LCGW phosphors doped by Eu3+, Tb3+, Dy3+ ions was studied. The results verified that the LCGW:Ln3+ (Ln = Tb, Eu, Dy) phosphors are promising for applications in white LEDs. [ABSTRACT FROM AUTHOR]

In this study, La 2 (MoO 4) 3 doped with Eu3+ was synthesized by the high-temperature solid-state method. The phase composition of the Eu3+-doped La 2 (MoO 4) 3 sample was confirmed by X-ray powder diffraction (XRD) analysis, and the microstructure was observed via the scanning electron microscopy (SEM). Under the excitation at 211 nm, the room temperature emission spectra of Eu3+ in the samples with different doping levels were recorded. In addition, the prepared La 2 (MoO 4) 3 : x Eu3+ (x = 0–0.25) phosphors were color tunable. A non-contact optical thermometer with high sensitivity and high-temperature resolution was fabricated based on the different thermal quenching behaviors of the Mo–O group and Eu3+ center. The fluorescence intensity ratio (FIR), temperature resolution (ΔT), maximum absolute and relative sensor sensitivity (Sa and Sr) of La 2 (MoO 4) 3 :Eu3+ were calculated according to different thermal quenching effects between room temperature (298K) and 573K of Eu3+ and Mo–O group. These results show that La 2 (MoO 4) 3 :Eu3+ has excellent sensitivity and temperature resolution, good reversibility and reliability, as Sa = 0.0525 K-1, Sr = 0.3724. % K−1, ΔT = 0.0806 K and the FIR error was only 0.62%. Therefore, the Eu3+-doped La 2 (MoO 4) 3 is a promising candidate material for high performance non-contact optical thermometers. [ABSTRACT FROM AUTHOR]

Tb 3+ -Sm 3+ co-doped Sr 9 Gd(PO 4 ) 5 (SiO 4 )F 2 (SGPSF) phosphors were prepared through a solid-state reaction, and their luminescence properties as well as energy transfer mechanism have been investigated in detail. The SGPSF:Tb 3+ , Sm 3+ phosphors system could be efficiently excited at wavelengths ranging from 200 to 500 nm, which is well matched with the spectra of near ultraviolet chips. The emission of SGPSF:Tb 3+ , Sm 3+ phosphor covers the entire visible region with sharp peaks in the blue, green, and red regions. The emission color of SGPSF:Tb 3+ , Sm 3+ could be adjusted from green (0.275, 0.378) to red (0.519, 0.295) by controlling the doping content of Sm 3+ /Tb 3+ . [ABSTRACT FROM AUTHOR]

In this paper, a series of novel luminescent Sr 10− x (SiO 4 ) 3 (SO 4 ) 3 O: x Eu 2+ phosphors with apatite structure were synthesized by a high temperature solid-state reaction. The phase structure, photoluminescence (PL) properties, as well as the PL thermal stability were investigated. Sr 9.92 (SiO 4 ) 3 (SO 4 ) 3 O:0.08Eu 2+ phosphor exhibits better thermal quenching resistance, retaining the luminance of 66.55% at 150 °C compared with that at 25 °C. The quenching concentration of Eu 2+ in Sr 10 (SiO 4 ) 3 (SO 4 ) 3 O was about 0.08 (mol) with the dipole–quadrupole interaction. The Sr 10− x (SiO 4 ) 3 (SO 4 ) 3 O: x Eu 2+ phosphors exhibited a broad-band green emission at 538 nm upon excitation at 396 nm. The results indicate that Sr 10− x (SiO 4 ) 3 (SO 4 ) 3 O: x Eu 2+ phosphors have potential applications as near UV-convertible phosphors for white-light UV LEDs. [ABSTRACT FROM AUTHOR]

In this paper, a series of novel luminescent Sr 1− x Al 12 O 19 : x Eu 2+ phosphors were synthesized by a high temperature solid-state reaction. The phase structure, photoluminescence (PL) properties, as well as the decay curves were investigated. The quenching concentration of Eu 2+ in SrAl 12 O 19 was about 0.15 (mol). Upon excitation at 378 nm, the composition-optimized Sr 0.85 Al 12 O 19 :0.15Eu 2+ exhibited strong broad-band green emission at 530 nm with the CIE chromaticity (0.2917, 0.5736). The results indicate that Sr 1− x Al 12 O 19 : x Eu 2+ phosphors have potential applications as green-emitting phosphors for UV-pumped white-light LEDs. [ABSTRACT FROM AUTHOR]