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The near‐infrared (NIR) persistent luminescence (PersL) materials have attracted widespread attention owing to the unique self‐sustained light with good penetrability. Currently, most of the reported NIR PersL materials are activated by Cr3+. Considering the potential toxicity of chromium ions, there is an urgent requirement to explore the Cr3+‐free NIR phosphors. Herein, a novel NIR phosphor Sr2LuSbO6:Fe3+ (SLSO:Fe3+) is prepared and its luminescence properties are systematically studied. The Fe3+‐activated Sr2LuSbO6 exhibits a long‐wavelength NIR emission band centered at 890 nm with a 110 nm full‐width at half maximum (FWHM), and its PersL can last over 18 h. The phosphor shows excellent PersL stability even after being dispersed in solutions of different environments for 7 days. Furthermore, the PersL emitted by the phosphor can penetrate the 2 cm thickness beef, evidencing its good NIR PersL penetration property. This work provides a novel NIR PersL materials based on Fe3+ luminescence for technological applications and also contributes to accelerate the development of new‐generation Fe3+‐doped NIR PersL phosphor toward versatile applications. [ABSTRACT FROM AUTHOR]

In this work, we prepared a new orange-red phosphor Li2La1−xTiTaO7:xSm3+ (abbreviated as LLTT:Sm3+) for white light-emitting diodes (w-LEDs). Its crystal structure, microstructure, photoluminescence characteristics, luminescence lifetime and thermal quenching properties were studied in depth. The LLTT:Sm3+ phosphor shows four intense emission peaks at 563, 597, 643, and 706 nm when excited at 407 nm. Thermal quenching is caused by the dipole–quadrupole (d–q) interaction of Sm3+ ions, and the optimum doping concentration of Sm3+ is x = 0.05. Meanwhile, the LLTT:0.05Sm3+ phosphor has a high overall quantum yield (QY = 59.65%) and almost no thermal quenching. The emission intensity at 423 K is 101.5% of the initial value at 298 K, while the CIE chromaticity coordinates barely change as the temperature rises. The fabricated white LED device exhibits excellent CRI and CCT values of 90.4 and 5043 K, respectively. These findings demonstrate that the LLTT:Sm3+ phosphor has promise in w-LED applications. [ABSTRACT FROM AUTHOR]

Cr3+-activated phosphors with high quantum efficiency show excellent promise in the field of near-infrared (NIR) phosphor converted light-emitting diodes (pc-LEDs). Here, we design an annealing program for Cr3+-doped phosphors containing variable valence elements that cannot be prepared in a reducing atmosphere to enhance their luminescence efficiency and thermal stability. A novel phosphor, Li2Mg3SnO6:Cr3+, developed by this annealing design, containing variable valence element Sn, exhibits higher quantum efficiency and better thermal stability than the one prepared by the conventional solid-state reaction. The Li2Mg3SnO6:0.03Cr3+ sample exhibits broadband NIR emission with a full width at half-maximum (FWHM) of 201 nm. After annealing, the internal quantum efficiency (IQE) and external quantum efficiency (EQE) of the Li2Mg3SnO6:0.03Cr3+ sample are enhanced from 48.5% to 84.7% and from 22.7% to 32.6%, respectively, and the thermal quenching temperature at which the luminescence intensity of the phosphor reduces to half of its initial value is promoted from ∼400 K to ∼425 K. The luminescence intensity of the optimized Li2Mg3SnO6:0.03Cr3+ sample at 425 K (∼152 °C) remains 49.2% of its initial intensity at 300 K. A NIR pc-LED is fabricated by combining the optimized Li2Mg3SnO6:0.03Cr3+ sample with a blue LED (455 nm blue chip), and the NIR radiant fluxes of 3.676 mW (at 10 mA) and 29.21 mW (at 100 mA), as well as a maximum NIR photoelectric efficiency of 14.2%, are obtained. The results show that this novel phosphor has great application potential in NIR pc-LEDs, and the annealing design exhibits huge potential for improving the optical properties of Cr3+-activated phosphors. [ABSTRACT FROM AUTHOR]

Phosphors have attracted significant interest as potential optical temperature sensors in recent years. In our work, a new blue-light stimulated KSr6Sc(SiO4)4:Eu2+ phosphor with decorative kröhnkite-like octahedral tetrahedral chains was successfully synthesized. Multiple site occupancy occurred in KSr6Sc(SiO4)4:Eu2+ and induced a yellow-orange emission band with a peak at 571 nm and an FWHM of 91 nm. Gaussian fitting and time-resolved photoluminescence mapping were combined to analyze the occupation of Eu2+ in five Sr2+ sites. In the meantime, the site occupation preference, energy transfer process, and thermal quenching mechanism of Eu2+ emission centers have been comprehensively examined. Under 450 nm excitation, the optimal sample possesses an acceptable quantum efficiency (EQE = 17.3%) and a high sensitivity between luminescence properties and temperature variation ranging from 200 to 475 K. The optimal sample's relative sensor sensitivity achieves a maximum value of 3.53% K−1 at 475 K. The phosphor KSr6Sc(SiO4)4:0.07Eu2+ presents the potentiality as an optical thermometer. [ABSTRACT FROM AUTHOR]

In this work, a series of novel, broadband, cyan-green emitting Ba3LuGa2O7.5:Bi3+ phosphors are prepared to bridge the cyan gap through a simple high-temperature solid-state reaction method. Their crystal structures, morphologies, luminescent properties, temperature-dependent emission spectra, temperature-dependent lifetime decay curves and quantum efficiencies were investigated in detail. Upon 351 nm excitation, the phosphor presents cyan-green emission with the main peak located at 500 nm, corresponding to the 3P1–1S0 transition of Bi3+ ions. The emission intensity of BLGO:0.02Bi3+ phosphors is greatly enhanced when introducing a suitable flux. The value of external quantum efficiency is advanced from 9.43% to 30.93%. According to the luminescence intensity and thermal quenching properties of the phosphor, the potential applications of BLGO:Bi3+ in the two fields of WLEDs and optical temperature sensing were explored. Since the excitation band of the phosphor can match well with that of the near-ultraviolet chip, combined with commercial phosphors, the BLGO:0.02Bi3+ phosphor is employed to obtain a full-spectrum WLED device with a higher color rendering index (CRI, Ra = 93.5), and a lower correlated color temperature (CCT, 4523 K). In the temperature range of 293 to 498 K, the relative sensitivities Sr and S are calculated to reach the maximum value of 2.05% K−1 and 2.21% K−1, respectively. These results indicated that the prepared BLGO:Bi3+ phosphors have potential application prospects as full-spectrum WLEDs and in temperature sensing. [ABSTRACT FROM AUTHOR]

A series of novel non-gallate near-infrared (NIR) Mg2InSbO6:Cr3+ phosphors were successfully prepared using the solid-state reaction method. With the strong crystal field, double-perovskite oxide Mg2InSbO6:Cr3+ under ultraviolet (UV) excitation exhibits intense NIR emission centered at 698 nm with an internal quantum efficiency of 70.8%. Apart from photoluminescence, NIR persistent luminescence can also be detected from the Mg2InSbO6:Cr3+ phosphor. The persistent luminescence from the optimized sample Mg2InSbO6:0.3 mol% Cr3+ can still be recognized after ceasing the 365 nm UV excitation for 24 h with the aid of a night-vision instrument. These phosphors can be photostimulated by NIR light rapidly to enhance the NIR signal. The persistent luminescence of Mg2InSbO6:Cr3+ can penetrate beef of 4 cm thickness, which suggests its great potential in biological imaging application. Based on the results of persistent luminescence and thermoluminescence, a feasible afterglow mechanism of the Mg2InSbO6:Cr3+ phosphor is proposed and discussed. The present work might provide a new perspective for developing novel NIR phosphors with high quantum efficiency and considerable persistent luminescence duration. [ABSTRACT FROM AUTHOR]

Bi3+ has gained increasing attention due to its abundant reserves, adjustable luminous colour and high chemical stability, therefore, Bi3+-activated luminescent materials have already been extensively applied in various fields. Herein, a novel blue-emitting CaNaSb2O6F:Bi3+ (CNSOF:Bi3+) phosphor with a pyrochlore-type structure with the space group Fd3¯m (277) was successfully synthesized. It exhibits a broad absorption band in the n-UV region (290–390 nm) and an ideal blue emission band centered at 441 nm. Interestingly, the wide emission peak of CNSOF:Bi3+ shows strongly temperature-dependent fluorescence properties and good thermal degradation resistance in the cycle temperature range from 298 K to 473 K, and the relative sensitivity is calculated to reach the maximum value of 2.34% K−1 at 423 K. Besides, the phosphor is different from a traditional optical temperature sensing material which shows the emission peak of trivalent rare earth ions. The wide emission peak makes the instrument insensitive to the peak shift, which dramatically reduces the requirement of the instrument, and the emission peak does not shift with the temperature to enhance the measurement stability, thus saving the cost. These results indicate that the CNSOF:Bi3+ blue emitting phosphor has potential applications in temperature sensing. [ABSTRACT FROM AUTHOR]