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Fingerprints are widely studied due to their unique shape and lifelong properties. The latent fingerprint (LFP) visualization is critical in identifying crime scenes and personal information. At present, the powder dusting method for LFP detection is favored due to its environmental friendliness and nontoxicity. However, this method has low resolution, low sensitivity, and large background interference. To address these shortcomings, the red-emitting Sr 2 MgMoO 6 :xEu 3+ (x = 0-0.50) phosphors were synthesized using the solid-state reaction process. The products were systematically studied through the structural phase, luminescent property, decay curve, and color purity. Sr 2 MgMoO 6 :xEu 3+ phosphors were monitored at 596 nm and exhibited a commendable broad excitation band between 250 and 475 nm. This result indicated that the disadvantage of the poor absorption of commercial red phosphors (Y 2 O 2 S:Eu 3+ ) in the near-ultraviolet region was overcome. Under excitation at 393 nm, the synthesized Sr 2 MgMoO 6 :Eu 3+ phosphor exhibited intense red light at 596 and 616 nm, due to the 5 D 0  →  7 F 1 and 5 D 0  →  7 F 2 transitions of Eu 3+ ions. The optimal concentration for the Sr 2 MgMoO 6 :xEu 3+ phosphor was x = 20 mol%, and the concentration quenching effect was ascribed to the dipole-dipole interaction. The Commission International del'Eclairage (CIE) chromaticity coordinates of Sr 2 MgMoO 6 :Eu 3+ were (0.643, 0.356), and the color purity was 99.8%. Furthermore, the fluorescent LFP images developed by Sr 2 MgMoO 6 :0.20Eu 3+ phosphors were well visualized, and level 1-3 details were well identified with high resolution, contrast, sensitivity, and selectivity. The obtained results suggested that the Sr 2 MgMoO 6 :Eu 3+ phosphor can be applied for LFP detection., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

A sequence of reddish‐orange emitting NaSrBi(1−x)TeO6:xSm3+ phosphors were successfully composited by a favorable solid‐phase chemical process. The sintering temperature is optimized as 850°C. NaSrBiTeO6 (NSBTO):Sm3+ samples were assigned to the cubic double‐perovskite structure, exhibiting the space group of Fm3¯$\bar{3}$m (225). Photoluminescence emission spectra display the main peaks at 562, 598, 645, and 705 nm at 404 nm excitation. Among them, the most intense emission peak is at 645 nm. The concentration‐quenching mechanism of Sm3+ follows the interaction between electric dipoles and quadrupoles. The asymmetric ratio (I(4G5/2‐6H9/2)/I(4G5/2‐6H5/2) of NSBTO:2 mol%Sm3+ phosphor is extracted as 4.96. The optimum NSBTO:2 mol%Sm3+ phosphor has excellent thermal stability with a remained emission intensity riches 93.61% (420 K). After testing with high‐pressure water steam at various periods, the phosphor remains chemically stable for moisture resistance. For the NSBTO:2 mol%Sm3+ phosphor, the satisfactory color purity and low correlated color temperature (CCT) are obtained with 99.9% and 1494 K, respectively. The electroluminescence spectra of the prepared red light emitting diode (LED) are in conformity with the phytochrome absorption spectra of chlorophyll a, chlorophyll b, PFR, and PR. The white light‐emitting diode (w‐LED) is also perfectly packaged, obtaining an efficient color rendering index (Ra) of 92.12 and CCT of 5553 K. These exceeding optical properties certified that NaSrBi(1−x)TeO6:xSm3+ demonstrates promising prospects and can be efficiently applied in horticultural LED applications. [ABSTRACT FROM AUTHOR]

A series of novel yellow-emitting antimonate-based Mg2InSbO6:xDy3+ (x = 0.5, 1, 2, 10, 15, and 25 mol%) phosphors was firstly synthesized by a solid-state reaction. The crystal structure, X-ray diffraction (XRD), photoluminescence (PL) properties, and the thermal quenching behaviours of prepared Mg2InSbO6:Dy3+ samples were exhaustively studied. The Mg2InSbO6 lattice has a trigonal crystal system, which possesses the R 3 ¯ (#148) space group. The as-prepared Mg2InSbO6:Dy3+ phosphors show a bright yellow emission peak at 572 nm under near-ultraviolet (n-UV) 349 nm excitation, which is attributed to the 4F9/2–6H13/2 transition of Dy3+. The optimum product is Mg2InSbO6:10 mol% Dy3+ with the estimated Rc = 13.05 Å. The optimum sample Mg2InSbO6:10 mol% Dy3+ exhibits abnormal thermal quenching phenomenon. The emission intensity reaches a maximum at 420 K. The fluorescence lifetime of Mg2InSbO6:10 mol% Dy3+ phosphor is measured to be 0.416 ms. Besides, the CIE chromaticity coordinates of Mg2InSbO6:xDy3+ (x = 0.5–25 mol%) phosphors change slightly, which possess low correlated color temperature (CCT) and high color purity. All findings suggest that Mg2InSbO6:Dy3+ samples can serve as white emission candidates for white light-emitting diodes (w-LEDs). [ABSTRACT FROM AUTHOR]

Sm3+ ions activated BaBiNaTeO6 phosphors were produced by the conventional high temperature solid-state reaction. The structures and phase purity, morphology, and luminescence properties of prepared BaBiNaTeO6: xSm3+ (x = 0.05–0.50 mol) were examined by X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence (PL). The BaBiNaTeO6:Sm3+ phosphor shows that orange-red emission (646 nm) under 404 nm excitation, while the associated absorption peaks are in the ultraviolet (UV) and near-ultraviolet (NUV) area. The quenching concentration of BaBiNaTeO6:Sm3+ phosphor is approximately 15 mol% as optimum doping concentration. The Commission Internationale de L'Eclairage (CIE) coordinates of BaBiNaTeO6:0.15Sm3+ are calculated to be (0.604, 0.393). Therefore, Sm3+-doped BaBiNaTeO6 phosphors can be applied in white light-emitting diodes (w-LEDs). [ABSTRACT FROM AUTHOR]

In this study, a series of novel yellow-emitting borate LiGd6(BO3)3O5 phosphors doped with different concentrations of Dy3+ ions were successfully synthesized via a high-temperature solid-state reaction. The LiGd6(BO3)3O5 lattice had a monoclinic crystal system, which possessed the P21/c space group. Under the excitation of 351 nm, the three dominant peaks of the LiGd6(BO3)3O5:Dy3+ centered at 488 (4F9/2-6H15/2), 578 (4F9/2-6H13/2), and 668 nm (4F9/2-6H11/2). The optimal doping concentration of Dy3+ ions in the LiGd6(BO3)3O5: xDy3+ phosphors was x = 0.02 mol, and the concentration quenching effect was ascribed to the dipole–dipole interaction. The prepared LiGd6(BO3)3O5:Dy3+ phosphor showed excellent thermal stability with high quenching temperature (T0.5 > 500 K) and activation energy (Ea = 0.27 eV). Besides, the CIE chromaticity coordinates of LiGd6(BO3)3O5:xDy3+ phosphors changed slightly, which possessed low correlated color temperature (CCT). The results indicated the great potential of LiGd6(BO3)3O5: Dy3+ phosphor to apply in w-LEDs. [ABSTRACT FROM AUTHOR]

High‐efficiency and far‐red light phosphors based on Mn4+‐doped inorganic luminescence materials are beneficial to plant cultivation. However, Mn4+‐doped oxide phosphors have a common problem of low quantum efficiency. Alkali metal ion codoping can effectively improve the luminescence properties of Mn4+‐activated oxide phosphors. Herein, a series of Sr2InSbO6:Mn4+, M (SISO:Mn4+, M) (M = Li+, Na+, and K+) far‐red‐emitting phosphors codoped alkali metal ions were first synthesized. Density functional theory calculation indicated that SISO is a kind of indirect bandgap material with a bandgap of ∼1.60 eV. The SISO:Mn4+ samples showed a far‐red light at 698 nm upon 365 nm, which perfectly matched the absorption spectrum of the far‐red‐phytochrome (Pfr) of plants. The doping concentration of the SISO:Mn4+ samples was optimized to be 0.006 mol. The concentration quenching mechanism was defined as dipole–dipole interaction by combining the Dexter theory and the Inokuti–Hirayama model. Optimizing the sintering temperature and codoped with alkali metal ions (Li+, Na+, and K+) could improve the luminescent intensity of SISO:Mn4+. The optimum sintering temperature was 1300°C. The internal quantum efficiencies of SISO:0.006Mn4+ and SISO:0.006Mn4+, 0.006Li+ phosphors are 22.67% and 60.56%, respectively. SISO:Mn4+, Li+ phosphors‐based plant growth light‐emitting diodes (LEDs) demonstrate excellent optical stability and long lifetime. Thus, these phosphors are promising candidates for plant cultivation LEDs. [ABSTRACT FROM AUTHOR]

In this study, Sm3+‐doped double‐perovskite Mg2InSbO6 phosphors were synthesized via high‐temperature solid‐state reaction. Mg2InSbO6 belongs to the double‐perovskite family with a space group of R3¯ (No.148). The photoluminescence (PL) spectrum illustrates that Mg2InSbO6:0.05Sm3+ phosphor can emit intense orange‐red emission light at 607 nm due to the 4G5/2→6H7/2 transition. The optimum concentration of Mg2InSbO6:xSm3+ is confirmed to 0.05 mol. The asymmetric ratio (4G5/2→6H9/2/4G5/2→6H5/2) of Mg2InSbO6:0.05Sm3+ phosphor is 2.73. The quenching temperature exceeds 500 K, illustrating that Mg2InSbO6:Sm3+ sample has excellent heat resistance. The high color purity and correlated color temperature (CCT) of Mg2InSbO6:Sm3+ phosphors are obtained. Furthermore, a white light‐emitting diode (w‐LED) is successfully fabricated, possessing CCT of 6769 K and high color rendering index (Ra) of 89. Therefore, the orange‐red‐emitting Mg2InSbO6:Sm3+ phosphors exhibit great potential to apply in solid‐state lighting fields. [ABSTRACT FROM AUTHOR]

This work was the first to synthesize the yellow-emitting phosphor La7Ta3W4O30:Dy3+ via a high-temperature solid reaction. The structure of La7Ta3W4O30:Dy3+ is trigonal crystalline pertaining to the R-3 (No.148) space group. Under 388-nm excitation, the photoluminescence spectrum of the La7Ta3W4O30:0.10Dy3+ sample exhibited four sharp peaks, which were attributed to 4F9/2–6H15/2 (480 nm), 4F9/2–6H13/2 (573 nm), 4F9/2–6H11/2 (658 nm), and 4F9/2–6H9/2 (753 nm) transitions. The optimal doping content of Dy3+ was 10 mol%, and the critical transfer distance (Rc) of the energy transfer between Dy3+ reached 22 Å. The concentration quenching mechanism involved the dipole–dipole interaction. The quenching temperature was higher than 450 K. The fabricated white light-emitting diode (W-LED) possesses a high color rendering index (Ra = 88), good correlated color temperature (5710 K), and chromaticity coordinates (0.328, 0.335) that are close to those of standard white light (0.333, 0.333). Therefore, this prepared phosphor is a potential candidate for W-LED applications. [ABSTRACT FROM AUTHOR]

The novel orange-red light emitting La 7 Ta 3 W 4 O 30 : x Sm3+ (x = 0.005–0.20) phosphors were synthesized via the solid-state reaction method. The crystal structure, photoluminescence (PL) properties, optimum concentration, color purity, decay life, and thermal stability of the samples were systematically studied. Under the excitation of 404 nm, La 7 Ta 3 W 4 O 30 :Sm3+ emits intense orange-red light at 597 nm. The PL spectra of La 7 Ta 3 W 4 O 30 :Sm3+ phosphors are ascribed to the 4G 5/2 to 6H J (J = 5/2, 7/2, 9/2, and 11/2) transitions of Sm3+ ions. The concentration quenching occurs at the doping level of 1 mol%. The quenching temperature is higher than 500 K. Finally, a white LED (w-LED) with the Commission Internationale de L'Eclairage (CIE) chromaticity coordinates of (0.312, 0.296) and good color rendering index (Ra) of 86 was fabricated. As a consequence, all the results suggest that the orange-red phosphors La 7 Ta 3 W 4 O 30 :Sm3+ have potential applications in w-LEDs structures. [ABSTRACT FROM AUTHOR]

A novel tantalate red‐emitting phosphors NaCa1‐xEuxTiTaO6 (x = 0.02‐0.50) is synthesized via the traditional solid‐state reaction sintering. The photoluminescence properties, X‐ray diffraction (XRD), scanning electron microscopy (SEM), and thermal stability are characterized in detail. Photoluminescence spectra show strong red emission monitored at 614 nm at λex = 395 nm. The spectral properties exhibit excellent color purity and chromaticity coordinate (CIE) characteristics. White light‐emitting diodes (w‐LEDs) device are fabricated by the prepared phosphors and show high quality of color‐rendering index. The investigated results suggest that the Eu3+‐doped NaCaTiTaO6 phosphors can be as potential substitute red phosphors for w‐LEDs. [ABSTRACT FROM AUTHOR]

Novel color-tunable Ca5(PO4)3Br:Eu2+,Mn2+ single component phosphors have been firstly synthesized through high-temperature solid-state reaction. X-ray diffraction (XRD), scanning electron microscopy (SEM), decay curves, and photoluminescence (PL) including temperature-dependent PL properties were used to characterize the as-prepared samples. Ca5(PO4)3Br:Eu2+ phosphors can be efficiently excited in the range of 250–450 nm, and give intense blue emission centering at 461 nm. A tunable color from blue to white and then to red was generated when Mn2+ ions were co-doped into the Ca5(PO4)3Br:Eu2+, which is based on the energy transfer from Eu2+ to Mn2+ ions. The energy transfer is demonstrated to be a dipole–quadrupole mechanism. The temperature dependent luminescence properties of Ca5(PO4)3Br:Eu2+ and Ca5(PO4)3Br:Eu2+,Mn2+ phosphors have been studied in detail. Furthermore, the fabricated white LED showed the chromaticity coordinate (0.314, 0.285), color rendering index of 83, and correlated color temperature of 6248 K. All phenomena demonstrate that Ca5(PO4)3Br:Eu2+,Mn2+ is a very promising candidate for use as UV white light-emitting diode (WLED) phosphor. [ABSTRACT FROM AUTHOR]

Novel Eu3+-activated orthosilicate NaYSiO4:xEu3+ (x = 0.02, 0.05, and 0.20) red-emitting phosphors were developed for white light emitting diode applications. The X-ray diffraction (XRD), photoluminescence excitation and emission spectra, temperature-dependent curves were applied to characterize the samples. The red emission of the NaYSiO4:Eu3+ phosphor corresponding to 5D0→7F2 (614 nm) transition was observed under the excitation of 394 nm wavelength, which is suitable for UV LED chip. The quenching temperature for NaYSiO4:0.05Eu3+ was found to be over 500 K. The CIE chromaticity coordinates of NaYSiO4:0.05Eu3+ are very close to the National Television System Committee (NTSC) standard red. [ABSTRACT FROM AUTHOR]

Abstract: A new phosphor of the type Gd8(1−x)Eu8 xV2O17 (x=0–1.0) was synthesized through the solid‐state reaction ceramics method. A pure phase formation was verified by using X‐ray powder diffraction measurements. The luminescence of Gd8V2O17:Eu3+ was investigated through optical and laser excitation spectroscopy. The luminescence curves were investigated in the temperature region 10 to 300 K. Gd8V2O17 shows a self‐activated luminescence under excitation with UV‐ and near‐UV light. The spectra, the decay lifetimes, and the thermal stability of Gd8(1−x)Eu8 xV2O17 (x=0.005–1.0) strongly depend on both the Eu3+ concentration and the temperature. The tunable luminescence is realized by controlling the Eu3+‐doping level to adjust the host energy‐transfer efficiency from the VO43− groups to the Eu3+ activators. At low Eu3+ concentrations (<30 mol %), the intensity and lifetime show an unusual change with an increase of the temperature from 10–300 K, that is, the luminescence experiences a straightforward enhancement. The energy transfer from the VO43− group to the Eu3+ ions could be accelerated with an increase of the temperature resulting in an unusual enhancement of the Eu3+ luminescence and lifetime. However, the emission of the Eu3+ ions decreased for highly Eu‐doped samples (>30 mol %) with an increase of the temperature. The luminescence mechanism was discussed on the basis of the charge‐transfer band of the Eu3+ ions, the doping concentration, and the proposed microstructures in the lattices. [ABSTRACT FROM AUTHOR]

A series of novel silicate-based red-emitting K4Ca1−xSi3O9:xEu3+ (x = 0.01-0.30) phosphors were successfully synthesized via a high-temperature solid-state reaction method for the first time. The compounds were crystallized in the cubic structure with the space group Pa3¯. The photoluminescence spectrum of K4CaSi3O9:Eu3+ phosphor shows four peaks assigned to the 5D0-7FJ (J = 0, 1, 2, 3 and 4) transitions of Eu3+ upon 396 nm excitation. Judd-Ofelt intensity parameters and CIE were calculated from the photoluminescence data. The quenching temperature for K4CaSi3O9:0.30Eu3+ was estimated to be above 500 K. The superior thermal stability can be attributed to the rigid structure of the host. The good color saturation and high thermal stability indicate that K4CaSi3O9:Eu3+ phosphor is a potential candidate for light-emitting diodes. [ABSTRACT FROM AUTHOR]

NaCa 2-2x Eu 2x Si 4 O 10 F (x = 0.01, 0.03, 0.04, 0.05, 0.06) ceramic phosphors were synthesized via the traditional solid-state reaction method. The framework of NaCaSi 4 O 10 F constructed by the double chains of optically inert [Si 4 O 10 ] ensures its rigid lattice strength. The sample prepared in air atmosphere showed the red luminescence transitions of 5D 0 →7F J (J = 0–4). The coexistence of Eu3+ and Eu2+ centers was observed in the samples prepared in a reducing atmosphere, that is, there are two broad emission bands peaked at 420 nm (Eu I 2+) and 535 nm (Eu II 2+) corresponding to the 4f65 d1 → 4f7(8S 7/2) transitions of Eu2+ centers together with the characteristic 4f→4f luminescent lines (570–720 nm) from the Eu3+ centers. The number of Eu I 2+ center is overwhelming, which replace the 6-coordinated Ca2+ in octahedral CaO 5 F. The weak Eu II 2+ center occupies the 7-coordinating cation site in CaO 5 F 2 polyhedra. The temperature-dependent luminescence intensities of the Eu2+ and Eu3+ centers were investigated. Eu I 2+ has a good thermal stability on temperature quenching. Eu II 2+ was suggested to a metastable Eu3+ ion binding an electron released from cation vacancies V Ca ′′ in the close vicinity, i.e., (Eu3++e) ([Eu II 2+]*), which can show band luminescence. Therefore, Eu II 2+ centre has a low temperature quenching. This is a potential single candidate used for white lighting application by combining contributions from both Eu3+ and Eu2+ ions. • NaCa 2 Si 4 O 10 F can act as a host for RE activated phosphor. • NaCa 2 Si 4 O 10 F:Eu3+ shows pure red-luminescence from 5D 0.→7F J (J = 0–4) transitions. • Samples prepared in a reducing atmosphere shows coexistence of Eu2+ and Eu3+. • There is an interesting occupation of Eu2+ centers on Ca sites in NaCa 2 Si 4 O 10 F. • This is a single phosphor combining both Eu2+ and Eu3+ for white luminescence. [ABSTRACT FROM AUTHOR]

This work reports a new luminescence host, Yb3+-condensed fluorosilicate apatite Sr 4 Yb 6 (SiO 4) 6 F 2. Pure and Eu3+-doped Sr 4 Yb 6 (SiO 4) 6 F 2 dense ceramics were prepared via the solid-state reactions. The apatite-like structural features were confirmed via XRD Rietveld refinements. The optical absorption, down-conversion (DC) and up-conversion (UC) luminescence, and dynamic decays of Sr 4 Yb 6-6x Eu 6 x (SiO 4) 6 F 2 (x = 0, 0.01, 0.05, 0.1, 0.15) were investigated. In the DC with UV-light excitation, near-IR emission efficiency of Sr 4 Yb 6 (SiO 4) 6 F 2 can be greatly enhanced by Eu3+-doping via significant energy transfer from Eu3+ ions to Yb3+. The luminescence mechanisms were explained on the cross-relaxation (CR) processes between Eu3+ donors and Yb3+ acceptors. Up-conversion (UC) luminescence was detected via 974 nm excitation into 2F 7/2 states of Yb3+, which occurs in green cooperative luminescence (CL) from Yb-pairs and UC red emissions of Eu3+ ions. Unlike the case of DC luminescence under UV light, CL of Yb3+ decreases quickly with the increase of Eu3+ doping; meanwhile, the up-converted red luminescence of Eu3+ shows only a small increase. The energy transfer mechanism was discussed via cross-relaxation between Yb3+ and Eu3+ ions. • Luminescence was investigated in new Yb3+-condensed silicate apatite host. • Near-IR is greatly enhanced by Eu3+-doping via efficient energy transfer from Eu3+ to Yb3+. • Cooperative green emission of Yb3+ and up-converted red luminescence of Eu3+ are reported. • Cross-relaxation mechanism related to up-conversion was discussed. [ABSTRACT FROM AUTHOR]

A novel high thermal stability blue-emitting phosphor, Tm3+-doped Ca 9 NaGd 2/3 (PO 4) 7 in white light-emitting diodes (W-LEDs) has been fabricated via solid-state technique. The phase and optical properties were systemically investigated. The obtained phosphor presented an intense blue emission (centered at 456 nm) originated from the 1D 2 → 3F 4 transition of Tm3+ at λ ex = 360 nm. The energy transfer mechanism was judged as an electric multipole interaction with quenching concentration and critical distance in the Ca 9 NaGd 2/3 (PO 4) 7 host. Moreover, the emission intensity of synthesized phosphor maintained 97.5% of the value of room temperature at 420 K indicating excellent thermal stability. The results validated the Ca 9 NaGd 2/3 (PO 4) 7 :Tm3+ phosphor can be utilized excellent blue-emitting candidate for W-LEDs. [ABSTRACT FROM AUTHOR]

Eu3+-doped bismuth lanthanum tungstate BiLaWO 6 phosphors were synthesized for the first time by a conventional solid-state reaction at 1273 K. By powder X-ray diffraction (XRD), the crystal structure of the phosphor was verified, which revealed its single-phase structure. Under the 467 nm wavelength excitation, the Eu3+-doped BiLaWO 6 phosphor powders showed red emission (617 nm) that was ascribed to the 5D 0 → 7F 2 transitions of Eu3+. The effects of concentration on luminescence properties indicated that the optimal doping concentration was x = 0.50 mol. The thermal stability by the emission intensities at various temperatures was verified, and the activation energy (E a) was approximately 0.29 eV. The luminescence lifetime was analyzed by the decay curve. The chromaticity coordinates of BiLaWO 6 :0.50Eu3+ were x = 0.650, y = 0.347, which had a high color purity at 99.2%. The phosphors had potential application for white light-emitting diodes. A novel BiLaWO 6 :Eu3+ phosphor shows red emission at 617 nm under the 467 nm wavelength excitation and a high color purity at 99.2%. Unlabelled Image • BiLaWO 6 :Eu3+ phosphors can be firstly synthesized via solid-state reaction. • The phosphor emits bright red light at 467 nm excitation. • The phosphor possesses high color purity at 99.2%. [ABSTRACT FROM AUTHOR]

A novel single-phase trivalent europium activated red-emitting SrLaNaTeO 6 phosphor was first synthesized in a process of traditional high-temperature solid-state. The phase purity, morphology, and spectroscopy of the prepared phosphor were analyzed. Under 395 nm excitation, the photoluminescence (PL) spectra of the SrLaNaTeO 6 :Eu3+ products mainly contained five dominant sharp peaks. The intense red emission peak at 615 nm was the typical 5D 0 →7F 2 electric dipole transition of Eu3+. The optimum product of high quenching concentration was the SrLaNaTeO 6 :0.90Eu3+, which reached a high internal quantum efficiency (IQE) of 90.6%. The SrLaNaTeO 6 :0.90Eu3+ was estimated to have R c of 6.57 Å and possessed high color purity of 100.0%. The phosphors exhibited excellent thermal stability and high activation energy (E a = 0.29 eV). The prepared white light-emitting diode (WLED) had a high color rendering index (CRI) R a of 92 and a low correlated color temperature (CCT) of 5008 K. In conclusion, the phosphors have potential as red components for WLEDs. [ABSTRACT FROM AUTHOR]

In this work, trivalent europium (Eu3+) ion activated K2Sr(MoO4)2 red phosphors have been synthesized through high-temperature solid-state reaction method at 750 ℃. Detailed analysis was conducted on the phase purity, morphology, and luminescence properties of the synthesized phosphors. X-ray diffraction (XRD) confirmed the successful formation of K2Sr(MoO4)2:Eu3+ phosphors with pure phase with space group С2/c. The photoluminescence (PL) spectroscopy was used to record the excitation and emission spectrum of Eu3+ activated K2Sr(MoO4)2 phosphor. Under the excitation of 280 nm, the resultant samples exhibited the characteristic emissions of Eu3+ ions corresponding to the 5D0→7FJ transitions. The optimal doping concentration of Eu3+ ions was determined to be 35 mol%. Concentration quenching mechanism was identified as the interaction of near-neighbor ions. The chromaticity coordinates of K2Sr(MoO4)2:35 mol%Eu3+ were (0.659, 0.340) with a corresponding high color purity of 99.8%. The prepared K2Sr(MoO4)2:35 mol%Eu3+ phosphor had good thermal stability with temperature quenching temperature (T0.5 > 420 K) and high activation energy (Ea = 0.267 eV). The exhaustive findings from this study form the basis for advocating the application of these phosphors in light-emitting devices. [ABSTRACT FROM AUTHOR]

A series of novel Sr5YTi3Nb7O30: x Eu3+ (x = 0.05–0.40) red-emitting phosphors were firstly synthesized using the high-temperature solid-state method. The X-ray diffraction (XRD) patterns demonstrate that the phosphors are pure phase with the space group P 4 bm of tetragonal system. Under the 395 nm excitation wavelength, the red emission of Sr5YTi3Nb7O30:Eu3+ phosphor is considered to be dominated by the 5D 0 →7F 2 transition at 613 nm. The asymmetry ratios (R/O) of Sr5YTi3Nb7O30: x Eu3+ (x = 0.05–0.40) phosphors are identified as 2.64–2.78, which contribute to the high color purity (99.5%–99.8%). The phosphor has good thermal stability with 0.17 eV of activation energy. The Commission International de L'Eclairage (CIE) coordinates of the w-LED nearly overlap with the standard white light (0.333, 0.333), the R a is as high as 90. Meanwhile, the features of fingerprint are simultaneously distinguished at three levels on aluminum foil by Sr5YTi3Nb7O30:0.30Eu3+ phosphor. In addition, the latent fingerprint on various nonporous substrates (stainless steel, glass, and plastic surfaces) were identified. In summary, the phosphor is feasible to apply in the w-LEDs and latent fingerprint detection. [ABSTRACT FROM AUTHOR]

The Mn4+-doped Ca2MgTeO6 (CMTO) far-red emitting phosphors with double perovskite-type structure were successfully synthesized. Upon near-ultraviolet (n -UV, 300 nm) light excitation, the as-prepared phosphors showed far-red light at 700 nm attributed to the 2E g →4A 2g transition of Mn4+ ion. The doping concentration of the CMTO: x Mn4+ samples was optimized to be 0.8 mol%. The relevant mechanism of concentration quenching was demonstrated as the dipole-dipole interaction. Furthermore, solid solution and impurity doping strategies were adopted to improve the far-red emission of the luminescence-ignorable CMTO:Mn4+ phosphor. Series of Ca 2 MgTe (1− y) W y O 6 :0.8 mol%Mn4+ (y = 0–100 mol%) solid solution and Ca 2− z Ln z MgTe 0.6 W 0.4 O 6 :Mn4+ (Ln = La, Y, and Gd, z = 10 mol%) phosphors were synthesized through the above two strategies. The luminescence intensity of the optimal Ca 1.9 Gd 0.1 MgTe 0.6 W 0.4 O 6 :Mn4+ phosphor was 13.7 times that of the CMTO:Mn4+ phosphor and 2.51 times that of red commercial phosphor K 2 SiF 6 :Mn4+. Notably, both CMTO:Mn4+ and Ca 1.9 Gd 0.1 MgTe 0.6 W 0.4 O 6 :Mn4+ phosphors exhibited remarkable thermal stability compared with most Mn4+-doped phosphors. Finally, the highly efficient Ca 1.9 Gd 0.1 MgTe 0.6 W 0.4 O 6 :Mn4+ phosphor was successfully applied in fabricating the warm white light diode (w-LED). This working along both lines strategy exhibited great potential for luminescence optimization of Mn4+-doped oxide phosphors. [ABSTRACT FROM AUTHOR]

Novel apatite-type NaCa 3 Bi(PO 4) 3 F: x Sm3+ (0.01 ≤ x ≤ 0.30) orange-red-light phosphors were synthesized through the solid-state method at high temperature. The crystal structure, energy band structure, density of state, phase purity, particle morphology, photoluminescence properties, thermostability, and luminescence decay of the phosphors were comprehensively characterized. When λ ex = 404 nm, the optimal NaCa 3 Bi(PO 4) 3 F:0.05 S m3+ phosphor showed the orange-red emission (597 nm). The NaCa 3 Bi(PO 4) 3 F:Sm3+ phosphors exhibited abnormal thermal quenching properties as their emission intensity increased by about 2.57% from 300 to 380 K. Their intensity at 440 K was still 1.01-fold stronger than that at room temperature. The abnormal thermal quenching mechanisms were well explained via the coordinate configuration scheme. The thermal activation energy (E a) was calculated to be 0.79 eV. The color purity of all the phosphors reached 99.9%. Ultimately, a white light-emitting diode (w-LED) was fabricated based on the tri-color RGB method. The color rendering index and the chromaticity coordinates of the fabricated w-LED were 89 and (0.310, 0.319), respectively. Thus, these high thermostability NaCa 3 Bi(PO 4) 3 F:Sm3+ orange-red phosphors can be potentially used in w-LED applications. [ABSTRACT FROM AUTHOR]

In this study, novel deep-red-emitting Mg 2 InSbO 6 :Mn4+ phosphors were prepared through a high-temperature solid-state reaction. The as-prepared phosphors belong to the perovskite structure with the space group of R 3 ‾ (No.148). The calculated energy gap value of Mg 2 InSbO 6 is ~1.788 eV. Emission spectrum of the Mg 2 InSbO 6 :0.3%Mn4+ was obtained under 301 nm excitation, which centered 665 nm due to the 2E g →4A 2g transition. The optimum concentration of Mg 2 InSbO 6 : x Mn4+ is confirmed to 0.3% mol, and the concentration quenching effect is ascribed to the dipole–dipole interaction. The relative temperature-dependent PL spectra demonstrate that phosphors possess commendable repeatability and high activation energy. The chromaticity shift diagram shows the phosphors have good resistance of color drifting. The Mg 2 InSbO 6 :0.3%Mn4+ phosphor has a high color purity of 99.8%. Furthermore, a red light-emitting diode is fabricated with Mg 2 InSbO 6 :0.3%Mn4+ phosphor and a 365 nm near-ultraviolet chip. The emission spectrum of the red LED is perfectly overlapped with plant pigments (chlorophyll a and chlorophyll b) absorption spectrum. Thus, Mn4+-activated Mg 2 InSbO 6 :Mn4+ phosphors have the potential to apply in plant-cultivation LEDs. [ABSTRACT FROM AUTHOR]

In this study, novel garnet-type yafsoanite tellurate Ca 3 Zn 3 (TeO 6) 2 :Sm3+ phosphors are successfully synthesized using the traditional high-temperature solid-state reaction. The phase purity of the obtained phosphors is analyzed by X-ray diffraction and Rietveld refinement studies. Morphological variations are also observed with the different concentrations of Sm3+ ions substitution, which is analyzed using Scanning Electron Microscopy (SEM). The photoluminescent properties of the phosphors are systematically investigated. Results show that the samples display the strongest emission peak at 612 nm under the near-ultraviolet (n-UV) 409 nm excitation. This peak can be ascribed to the 4G 5/2 → 6H 7/2 transition of Sm3+. The Ca 3 Zn 3 (TeO 6) 2 :Sm3+ phosphor shows a high color purity, exhibits excellent thermal stability and good color drifting resistance. Furthermore, red and white light-emitting diodes have been successfully prepared. The white light-emitting diodes (w-LEDs) demonstrates a high color rendering index (CRI, R a) and low correlated color temperature (CCT). This study introduces a new orange-red-emitting phosphor and discusses its application in herb-growth w-LEDs. [ABSTRACT FROM AUTHOR]

A double-perovskite Sr 3 TeO 6 :Eu3+ red phosphor was successfully prepared and confirmed to be a single phase through X-ray diffraction. Under an optimal excitation wavelength (394 nm), the Sr 3 TeO 6 :Eu3+ phosphor emitted intense red light at 617 nm, which corresponded to 5D 0 →7F 2 transition. When the concentration of Eu3+ exceeded the optimal doping concentration (25 mol%), concentration quenching occurred because of the interactions among the nearest neighbor ions. The phosphor exhibited excellent thermal stability, and the E a value was 0.27 eV. In accordance with Judd–Ofelt theory, the low symmetry of Eu3+ ions was confirmed, and it resulted in a color purity of up to 99.5%–99.8%. Among the charge compensators (Li+, Na+, and K+), the Na+ ions had the best charge compensation effect. The luminescence intensity of Sr 3 TeO 6 :Eu3+, Na+ was approximately 2.06 times that of Sr 3 TeO 6 :Eu3+ and 2.25 times that of commercial phosphor (Y 2 O 3 :Eu3+). The fabricated red LED has the potential to be used for plant and herb cultivation. A white light–emitting diode (w–LED) was successfully prepared, and related parameters were established. The R a value of the prepared w–LED was as high as 91, and R 9 was 5.7 times that of a commercial w–LED. These characteristics indicate that phosphors have potential in the solid-state lighting field. [ABSTRACT FROM AUTHOR]

LaTiSbO 6 : x Eu3+ (x = 0∼)1.0) phosphor with a typical PbSb 2 O 6 -related structure was prepared through a facile solid-state ceramic routine, and morphology measurements and structural Rietveld refinements were conducted. Results show that LaTiSbO 6 : x Eu3+ (x = 0–0.4) phosphors formed a single trigonal phase (T-phase, space-group of P-31 m , No.162). The increase of Eu3+ doping (x = 0.5–0.6) can induce the formation of a second phase formation, that is, orthorhombic structure (O-phase) with space-group P nma (No. 62). Meanwhile, heavily doped LaTiSbO 6 : x Eu3+ (x = 0.6–1.0) was crystallized into a single orthorhombic structure (O-phase). LaTiSbO 6 had a direct transition and the band gap was 2.97 eV. The luminescence properties of LaTiSbO 6 : x Eu3+ (x = 0–1.0) were investigated at different doping levels. Eu3+-doping remarkably modified the band structure, resulting in the blue-shift of optical absorption, and the intrinsic blue emission of LaTiSbO 6 peaked at 465 nm. Doping concentration exerted interesting influences on the optical properties of the phosphors, such as narrowed band gap, tunable red-emitting, dominant blue excitation wavelength, and thermal stability of the luminescence. Eu3+ ion was applied as a spectroscopic probe for the investigation of the relationship between luminescence and crystal microstructure. Image 1 • LaSbTiO 6: x Eu3+ (x = 0–1.0) phosphors with typical PbSb 2 O 6 -type were developed. • Phase formation and band structure can be modified via on the doping levels. • The tunable red-emitting has a dependence on the doping levels. • LaSbTiO 6: x Eu3+ phosphor has extremely strong excitation in the blue wavelength region. • The phosphor presents a good stability on thermal quenching. [ABSTRACT FROM AUTHOR]

In the present work, a novel Eu3+-doped SrBi 2 Ta 2 O 9 red-emitting phosphor has been successfully synthesized by solid-state reaction. The X-ray diffraction (XRD) and luminescence properties of SrBi 2 Ta 2 O 9 have been investigated in detail. Under the excitation of λ = 395 nm and λ = 465 nm, the phosphor can emit bright red light at 615 nm due to 5D 0 →7F 2 transition. The optimal doping concentration and the thermal stability are investigated. Compared with reported commercial Y 2 O 2 S:Eu3+, Y 2 O 3 :Eu3+, the Commission International de L'Eclairage (CIE) coordinates of the red phosphor SrBi 2 Ta 2 O 9 :0.10Eu3+ are much closer to the standard of the National Television System Committee (NTSC). The value of color purity is 97%. The luminescence lifetime of SrBi 2 Ta 2 O 9 :Eu3+ is measured. Moreover, the white light emitting diode (w-LED) can be manufactured on the basis of InGaN. The chromaticity coordinates of combined w-LED are (0.327, 0.350), which approximates the equal energy point (0.333, 0.333). [ABSTRACT FROM AUTHOR]

Highlights • Ba 2 YAlO 5 :Eu3+ red-emitting phosphor was prepared. • The excitation spectrum matches well with near-UV LED chips. • The phosphor shows excellent thermal-stability. • The red-emitting LED was fabricated based on the InGaN chip. Abstract A series of novel Eu3+ activated aluminate Ba 2 Y 1− x Eu x AlO 5 (x = 0.02–0.40) red-emitting phosphors were synthesized through a high-temperature solid-state route at 1380 °C. The phosphors were well crystallized in the space group P 2 1 /c (No. 14). Their photoluminescence emission (PL) and excitation (PLE) spectra were investigated. The results indicate that the Ba 2 YAlO 5 :Eu3+ phosphor can be excited effectively under 394 nm irradiation, which is suitable for UV LED chip. The obtained Ba 2 YAlO 5 :Eu3+ phosphor shows four peaks, corresponding to the 5D 0 –7F J (J = 0, 1, 2, 3 and 4) transitions of Eu3+ upon 394 nm excitation. The optimal doping concentration of Eu3+ in Ba 2 YAlO 5 : x Eu3+ was determined at 30 mol%. By temperature dependent emission spectra, the quenching temperature for Ba 2 YAlO 5 :0.30Eu3+ was found to be over 500 K. And the CIE chromaticity coordinates of Ba 2 YAlO 5 :0.30Eu3+ are very close to the National Television System Committee (NTSC) standard red. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A novel single-phased Ca 9 LiGd 2/3 (PO 4) 7 : x Dy3+ phosphor was firstly synthesized. • Its structure, luminescent properties are well studied and characterized. • It was promising as a single-component white-light-emitting phosphor for w-LEDs. Abstract Novel single-phased white-light-emitting Ca 9 LiGd 2/3 (PO 4) 7 : x Dy3+ (x = 0.02, 0.05, 0.10, 0.15, 0.20, 0.25, and 0.30) β-Ca 3 (PO 4) 2 -type phosphate phosphors were synthesized. The phase structure, luminescence, and thermal stability of the phosphors were characterized by X-ray powder diffraction analysis, photoluminescence excitation and emission spectra, thermal quenching, and decay curves. XRD analysis confirmed the phase formation of Ca 9 LiGd 2/3 (PO 4) 7 :Dy3+ materials. Under the excitation of 352 nm, the emission of the Ca 9 LiGd 2/3 (PO 4) 7 :0.20Dy3+ sample centered at blue (488 nm) and yellow (580 nm), which corresponded to 4F 9/2 –6H 15/2 transition and 4F 9/2 –6H 13/2 transition. The optimum dopant concentration of Dy3+ ions was around 20 mol%, and the critical transfer distance of Dy3+ was calculated as 18 Å. The thermal-quenching temperature was above 500 K for Ca 9 LiGd 2/3 (PO 4) 7 :0.20Dy3+. The developed phosphor has a great potential as a single-component white-light-emitting phosphor for UV-light-emitting diodes. [ABSTRACT FROM AUTHOR]

A series of novel Eu 3+ -doped LiSrBiTeO 6 red-emitting phosphors were prepared by the solid-state reaction method for the first time. Its crystal structure and luminescence properties are investigated. X-ray powder diffraction patterns in combination with the Rietveld method reveal its single phase structure. The phosphor can be efficiently excited by 394 nm and 465 nm light and emits bright red luminescence at 616 nm corresponding to the electric dipole transition 5 D 0 – 7 F 2 . The optimal doping concentration of LiSrBi 1- x TeO 6 : x Eu 3+ is about 40 mol%. The thermal stability of the phosphor was tested by measuring their temperature-dependent emission intensities. The warm white light LEDs was fabricated based on the InGaN-chip. The chromaticity coordinates of fabricated w-LED are (0.344, 0.381). All results indicated that LiSrBiTeO 6 :Eu 3+ phosphors have potential application as red phosphors in white light emitting diodes. [ABSTRACT FROM AUTHOR]

Novel single-phased white-light-emitting Li 3 Gd 3 Te 2 O 12 : x Dy 3+ ( x  = 0.005, 0.01, 0.02, 0.05, 0.08, 0.10, and 0.15) garnet-type tellurate phosphors were firstly synthesized. The X-ray powder diffraction analysis, photoluminescence excitation and emission spectra, thermal quenching, and decay curves were applied to investigate the phase structure, luminescence, and thermal stability properties. Under the excitation of 351 nm, the emission of Li 3 Gd 3 Te 2 O 12 :0.02Dy 3+ sample centered at blue (488 nm) and yellow (580 nm), corresponding to 4 F 9/2 – 6 H 15/2 transition and 4 F 9/2 – 6 H 13/2 transition, respectively. The optimum dopant concentration of Dy 3+ ions in Li 3 Gd 3 Te 2 O 12 : x Dy 3+ was around 2 mol%. The thermal-quenching temperature was above 500 K for Li 3 Gd 3 Te 2 O 12 :0.02Dy 3+ . The tunable white light and correlated color temperature can be achieved in the present Li 3 Gd 3 Te 2 O 12 : x Dy 3+ phosphors by adjusting the yellow to blue intensity ratio based on the concentration of Dy 3+ ions. The fabricated warm white LED indicates the phosphor could be a single-component white light-emitting phosphor for UV light-emitting diodes. [ABSTRACT FROM AUTHOR]

Novel orange-red Sr 3 LaNb 3 O 12 (SLNO): x Sm3+ (0.01 ≤ x ≤ 0.03) phosphors are successfully prepared using the traditional solid-state method. The feasibility that the SLNO compounds can act as an appropriate host has been effectively demonstrated by unit cell structure and bandgap structure. The phase purity, particle size distribution, and elemental composition of SLNO:Sm3+ phosphors are studied. The luminescence properties, concentration-quenching mechanism, color purity, thermostability, CIE chromaticity coordinates, and correlated color temperature (CCT) of the obtained SLNO:Sm3+ products are also discussed. Under 408 nm excitation, SLNO:0.10Sm3+ sample emits a bright orange-red light at 598 nm owing to the 4G 5/2 to 6H 7/2 transition of Sm3+. The concentration-quenching mechanism is found to be dipole-dipole interaction by the calculated R c value (17.12 Å) and Dexter's theory. Impressively, the color purity of the phosphors is high and stable (all reach 99.9%), which is rarely affected by the Sm3+ doping concentration. It is worth noting that the obtained phosphors exhibit an abnormal thermal quenching (ATQ) behavior, increasing by 16.12% from 300 to 380 K (SLNO:0.10Sm3+). The CIE x and y chromaticity coordinates vary slightly with the change of temperature, indicating a good thermostability. The mechanism of ATQ has been studied as the lattice defects, and the thermal activation energy is calculated to be 0.51 eV. Ultimately, a white-light-emitting diode (w-LED) with a high color rendering index (R a) of 88 and a CIE chromaticity coordinate of (0.333, 0.333) has been prepared. The results above reveal the potential of SLNO:Sm3+ to be widely used in w-LEDs. • The SLNO:Sm3+ phosphors show superior color purity (99.9%). • The SLNO:Sm3+ phosphors have excellent thermal stability (E a = 0.51 eV). • The synthesized phosphors exhibit the abnormal thermal quenching behavior. • The fabricated w-LED exhibits a high color rendering index (R a = 88). [ABSTRACT FROM AUTHOR]

In this work, a series of double perovskite red-emitting NaSrLaTeO 6 : x Sm3+ phosphors were successfully synthesized through the traditional high-temperature solid-state method. The NaSrLaTeO 6 lattice has a cubic structure, which possesses the F m-3m (225) space group. Under 406 nm excitation, NaSrLaTeO 6 :Sm3+ phosphors can exhibit four emission peaks at 564, 599, 645, and 711 nm, which are ascribed to the 4G 5/2 →6H J (J = 5/2, 7/2, 9/2, and 11/2) transitions. The asymmetry ratio of NaSrLaTeO 6 :5 mol%Sm3+phosphor is calculated to be 6.11. The CIE chromaticity coordinates of NaSrLaTeO 6 : x Sm3+ (1 mol% ≤ x ≤ 30 mol%) phosphors change slightly with the increase in doping concentrations. The phosphors possess low correlated color temperature (CCT) and high color purity (>99.6%). The prepared NaSrLaTeO 6 :5 mol%Sm3+ phosphor shows the excellent thermal stability with a high quenching temperature (T 0.5 > 500 K) and activation energy (E a = 0.31 eV). Furthermore, the NaSrLaTeO 6 :Sm3+ phosphors have the good resistance to color drifting (chromaticity shift Δ E = 0.011 at 420 K). The w-LED was fabricated with a 402 nm chip through the trichromatic method. It has good CIE chromaticity coordinates (0.325, 0.310), high R a (89), and CCT (5889 K). Consequently, the red-emitting NaSrLaTeO 6 :Sm3+ phosphors would be anticipated to be used in w-LEDs. • The NaSrLaTeO 6 :Sm3+ phosphors have been firstly synthesized via high temperature solid-phase method. • The NaSrLaTeO 6 :Sm3+ phosphors have excellent thermal stability (T 0.5 > 500 K). • The synthesized phosphors exhibit a high color purity (99.6%). • The fabricated w-LED exhibits a high color rendering index (R a = 89). [ABSTRACT FROM AUTHOR]

Recently, rare-earth doped phosphors have shown great promise in phosphor-converted light-emitting diodes (pc-LEDs) for horticultural and white lighting applications. Herein, a deep red-emitting tungstate phosphor, CaGdSbWO 8 (CGSW):Sm3+ was obtained by a high-temperature solid-state reaction. The phosphor showed deep red-light emission at 647 nm, which was attributed to the 4G 5/2 –6H 9/2 transition of Sm3+. Surprisingly, this phosphor displays excellent thermal stability. The emission intensity of the best sample doped with 0.05 mol Sm3+ was 93.95% at 480 K. Ultimately, the fabricated red LED revealed superior spectral matching with the plant pigments (chlorophyll A and chlorophyll B), high color purity (99.9%), and CIE chromaticity coordinates (0.630, 0.370). Moreover, the white light-emitting diode (w-LED) can be manufactured by the tri-chromatic method with a 410 nm chip, which has a high color rendering index (R a = 88), CIE coordinates (0.336, 0.328). Thus, the Sm3+-doped CaGdSbWO 8 tungstate phosphors have extensive application potential in the field of pc-LEDs. • The CaGdSbWO 8 :0.05Sm3+ phosphor displayed the excellent thermal stability. • The phosphors showed deep red-light emission at 647 nm. • The fabricated w-LED had an appropriate CCT (5305 K) and high R a (88). • The fabricated red LED revealed superior spectral matching with the plant pigments. [ABSTRACT FROM AUTHOR]

• CaBi 2 Nb 2 O 9 :Eu3+ phosphors have been synthesized via solid-state reaction firstly. • IQE of the CaBi 2 Nb 2 O 9 :0.20Eu3+ phosphor under an excitation of 395 nm reached 71.37%. • CaBi 2 Nb 2 O 9 :0.20Eu3+ phosphors can be applied in various substrates for LFPs visualization. • The fluorescent LFPs developed with the CaBi 2 Nb 2 O 9 :0.20Eu3+ phosphor has the long-term photostability. Fingerprints have been effectively used in forensic surveys to identify individuals and provide information. The CaBi 2(1− x) Nb 2 O 9 :2 x Eu3+ powders were successfully fabricated by a convenient solid-state reaction. The crystal structure, particle morphology, luminescent properties, thermal stability, and ridge-shape details were investigated comprehensively. The X-ray diffraction graphs indicated that the CaBi 2(1− x) Nb 2 O 9 :2 x Eu3+ phosphors crystallized the orthorhombic phase. Photoluminescence emission spectra displayed an intense peak at 616 nm upon an excitation of 395 nm. The predominant concentration-quenching principle of Eu3+ followed the electric dipole–dipole interaction. The thermal-quenching temperature (T 0.5) exceeded 420 K. Internal quantum efficiency (IQE) of the CaBi 2 Nb 2 O 9 :0.20Eu3+ sample reached 71.37%. The right whorl of latent fingerprint (LFP) was also observed clearly on substrates (aluminum foil, glass, and plastic) under a UV of 395 nm and sunlight illumination using optimized CaBi 2 Nb 2 O 9 :0.20Eu3+ samples. These results demonstrate that CaBi 2(1− x) Nb 2 O 9 :2 x Eu3+ phosphors have fingerprint identification application prospects. [Display omitted] [ABSTRACT FROM AUTHOR]

• Sr 3 WO 6 :Sm3+ phosphors can be firstly synthesized via solid-state reaction. • The phosphor emits bright orange-red light at 407 nm excitation. • The phosphor possesses excellent thermal stability. • The w-LEDs exhibit good color rending index and low correlated color temperature. Over the years, phosphor-converted white light-emitting diodes (pc-WLEDs) have attracted much attention due to their excellent luminescent performance. Meanwhile, there is an intent requirement for studying novel red phosphors for WLED with good luminescence properties and without harsh synthesis methods. In this work, a kind of novel double perovskite Sr 3 WO 6 :Sm3+, Na+ phosphor was synthesized with a solid-state reaction. The phase purity, morphology, luminescent properties of synthesized phosphors were investigated systematically. At 407 nm excitation, the Sr 3 WO 6 :Sm3+, Na+ phosphors exhibited orange-red light (655 nm) attributed to the transition of 4G 5/2 → 6H 7/2. The optimal doping concentration was 0.02 mol. The quenching temperature (T 0.5) of Sr 3 WO 6 :0.02Sm3+, 0.02Na+ phosphor was beyond 500 K, which showed the excellent thermal stability of this phosphor. A WLED was fabricated with the phosphor, and related parameters were obtained. The fabricated WLED had a high general color rendering index (R a = 89) and good correlated color temperature (CCT) (5297 K). Therefore, Sr 3 WO 6 :Sm3+, Na+ phosphors were promising candidates for near-ultraviolet (NUV) chip-based WLED and solid-state lighting. [ABSTRACT FROM AUTHOR]

In this study, novel layered niobate KCa 2 Nb 3 O 10 :Sm3+ orange red phosphors have been successfully prepared by adopting the molten-salt method. The phase purity, surface morphology, photoluminescence properties, thermal stability, and fluorescence lifetime are systematically demonstrated. The X-ray diffraction (XRD) analysis revealed that these powders were pure phase and crystallized in an orthorhombic with a space group of Cmcm (No.63). Under 407 nm excitation, the KCa 2 Nb 3 O 10 :Sm3+ phosphors have the strongest emission peak at 603 nm which can be put down to the 6H 5/2 → 4F 7/2 transition of Sm3+. The optimum concentration of KCa 2 Nb 3 O 10 : x Sm3+ is 5 mol%. The KCa 2 Nb 3 O 10 :Sm3+ phosphors display excellent thermostability because of their high T 0.5 (over 480 K). Meanwhile, these samples show a high color purity from 96.6 to 98.2%. The white light-emitting diodes (w-LEDs) have been prepared with flying colors. All the results indicated that the potential application of the new kind of KCa 2 Nb 3 O 10 :Sm3+ luminescent powder in w-LEDs. • The KCa 2 Nb 3 O 10 :Sm3+ phosphors show a good energy transfer. • The KCa 2 Nb 3 O 10 :Sm3+ phosphors have excellent thermal stability (E a = 0.17 eV). • The synthesized phosphors exhibit the superior color purity (98.2%). • The fabricated w-LED exhibits a high color rendering index (R a = 90). [ABSTRACT FROM AUTHOR]

• Sr 2 InSbO 6 :Eu3+ phosphors have been synthesized via solid-state reaction firstly. • The Sr 2 InSbO 6 :Eu3+ phosphor emits intense orange-red light at 395 nm excitation. • The WLED fabricated by the phosphor exhibits a high R a of 89 and a good CCT. • The Latent fingerprint fluorescent images developed by Sr 2 InSbO 6 :Eu3+@OA phosphors can be well visualized, and the level 1–3 details are well identified. Eu3+-activated Sr 2 InSbO 6 (SISO) orange-red-emitting double-perovskite antimonate phosphors were realized. The emission spectrum of SISO:Eu3+ sample exhibited a strong orange-red emission band at 594 nm under 395 nm excitation. Judd-Ofelt theory analysis indicated the Eu3+ ions were in the symmetrical environment of SISO host lattice. The fabricated white light-emitting diode presents a high R a and a good CCT. For the visualization of latent fingerprints (LFPs), the hydrophilic SISO:Eu3+ phosphor was converted into hydrophobic SISO:Eu3+@OA phosphor by coating oleic acid (OA). The SISO:Eu3+@OA phosphor could show reliable level 1–3 fluorescent images of LFPs with high contrast and resolution. The LFPs still exhibited the excellent visualization on the various substrates (glass, aluminum foil, stainless steel, compact disk, student card, and so on). These results indicate the SISO:Eu3+ products have great potential applications for WLEDs and visualization of LFPs. [Display omitted] [ABSTRACT FROM AUTHOR]

Novel orange-red phosphors Gd 2 InSbO 7 :Sm3+ were successfully prepared through the conventional high-temperature-solid state reaction. The phase purity, size distribution, luminescence properties, and decay curves are characterized in detail. Gd 2 InSbO 7 :Sm3+ phosphors possess a cubic structure with F d-3m (227) space group. Through the X-ray diffraction analysis, the obtained phosphors are identified to be pure phases. The Gd 2 InSbO 7 :Sm3+ phosphors emit a bright orange-red emission light at 605 nm, which is ascribed to the 4G 5/2 -6H 7/2 transitions. The asymmetry ratio R is confirmed to be 1.88, and the optimum concentration of Gd 2 InSbO 7 : x Sm3+ is confirmed to be 5 mol%. The activation energy E a is calculated to be 0.20 eV. Furthermore, the Gd 2 InSbO 7 :0.05Sm3+ phosphor possesses high color purity (100%). A white light-emitting diode (W-LED) is successfully fabricated, possessing good color rendering index (R a) and correlated color temperature (CCT). All results indicate that the Gd 2 InSbO 7 :Sm3+ phosphors have a potential to apply in the W-LEDs field. • Gd 2 InSbO 7 :Sm3+ phosphors are firstly synthesized via solid-state reaction. • The phosphor emits bright orange-red light at 405 nm excitation. • The phosphor exhibits good thermal stability and high color purity. • The W-LED exhibits high color rending index. [ABSTRACT FROM AUTHOR]

• The CISO:Sm3+ phosphors shows the zero-thermal-quenching characteristic. • The relationship between local symmetry and luminescence properties is studied. • The fabricated w-LED exhibits the superior color rendering index (R a = 93). • This work initiates a new insight to construct thermally stable phosphors. A material's structure vitally affects its luminescence property, which in turn determines its application. Therefore, understanding the correspondence between structural local symmetry and luminescence characteristics is vital for the design and synthesis of optical materials. A series of solid solution reddish-orange-emitting phosphors Ca 2 InSbO 6 :Sm3+ (CISO:Sm3+) was synthesized by the high-temperature solid-phase method and applied for white-light-emitting diodes (w-LEDs). Under 407 nm excitation, CISO:Sm3+ phosphors showed intense reddish-orange emission at 600 nm that is attributed to the 4G 5/2 → 6H 7/2 transition of Sm3+ ions. Given that Sm3+ ions are a structural probe, the relationship between their local symmetry and luminescence properties was discussed in detail. The photoluminescence intensity of CISO:Sm3+ phosphors continuously increases with rising temperature from 298 to 480 K based on the enhanced local symmetry. This phenomenon was further analyzed using the trap theory and charge compensation mechanism. High color purity (~99.9%) and proper Commission International del′Eclairage (CIE) chromaticity coordinates were achieved for the CISO:Sm3+ phosphors. Finally, the fabricated w-LED displayed superior color rendering index (R a = 93) and CIE chromaticity coordinates (0.330, 0.357) and thus has great potential as reddish-orange-emitting substitutes in horticultural and solid lighting. This work initiates a new insight to construct thermally stable phosphors for optical applications. [ABSTRACT FROM AUTHOR]

Deep-red emitting CaY 0.5 Ta 0.5 O 3 :Mn4+ phosphors were obtained by optimizing the reaction temperature. The structure of CaY 0.5 Ta 0.5 O 3 :Mn4+ consisted of a double perovskite with the Pnma (62) space group. The luminescence intensity of the synthesized CaY 0.5 Ta 0.5 O 3 :0.3%Mn4+ at 1550 °C was twice as strong as that at 1500 °C. The photoluminescence spectra of the synthesized CaY 0.5 Ta 0.5 O 3 :Mn4+ phosphor exhibited a deep-red broadband luminescence from 650 nm to 750 nm with a 680 nm dominated peak due to the 2E g →4A 2g transition of Mn4+ in TaO 6 octahedral structures. The optimal concentration for the CaY 0.5 Ta 0.5 O 3 : x Mn4+ phosphor was 0.3 mol.%. The concentration quenching effect was ascribed to the dipole–quadrupole interaction. The decay time (0.398–0.171 ms) indicated that the forbidden character of 3d transitions existed among Mn4+. The crystal field strength and the Racah parameters were discussed to estimate the nephelauxetic effect of Mn4+ in the CaY 0.5 Ta 0.5 O 3 host. Besides, the red light-emitting diodes (LEDs) were packaged using the CaY 0.5 Ta 0.5 O 3 :0.3%Mn4+ phosphor and a 368 nm near-ultraviolet chip. The emission spectrum of the red LED overlapped with the absorption curves of chlorophylls a and b. Results indicated that the CaY 0.5 Ta 0.5 O 3 :Mn4+ can serve as a component of the deep-red light in plant-growth LEDs. • The best reaction temperature and optimum concentration of Mn4+ ions in CaY 0.5 Ta 0.5 O 3 compound were found. • The phosphor emits bright red light excited by 309 nm. • The phosphor exhibits high color purity, and the red LEDs exhibit low correlated color temperature. • The main mechanism of energy transfer was identified. [ABSTRACT FROM AUTHOR]

Novel orange-red-emitting tantalate NaCaTiTaO 6 (NCTT): x Sm3+ (x = 0.005–0.25) phosphors are synthesized via a solid-state reaction technique at 1300 °C. The phosphors exhibit an orthorhombic perovskite structure with a space group of Pnma (No. 62). At 407 nm excitation, the phosphors show the strongest emission peak at 647 nm belonging to the 4G 5/2 → 6H 9/2 transition. The optimal Sm3+ concentration is 0.05 mol, and concentration quenching is caused by dipole–dipole interaction. The NCTT:0.05Sm3+ phosphor exhibit a broad bandgap of 3.44 eV and a high color purity of 99.9%. At 420 K, the decrease in intensity is only 10% of the initial value at 300 K for NCTT:0.05Sm3+ phosphor but 15% for Y 3 Al 5 O 12 :Ce3+ phosphor. Consequently, the fabricated white light-emitting diodes exhibit a high rendering index value of 89, a good correlated color temperature of 5257 K, and CIE coordinates of (0.339, 0.364). Hence, the Sm3+-doped orange-red-emitting NCTT phosphors have potential applications for w-LEDs. • NaCaTiTaO 6 :Sm3+ phosphors are firstly synthesized via solid-state reaction. • The phosphor emits bright orange-red light excited by 407 nm. • The phosphor exhibits excellent thermal stability and high color purity. • The w-LEDs exhibit good color rending index and low correlated color temperature. [ABSTRACT FROM AUTHOR]

Novel Sm3+-doped double perovskite Ca 2 MgTeO 6 orange-red emitting phosphors were prepared using solid-state reaction at 1100 °C. The powder phase purity, particle morphology and size, elemental composition, and luminescence properties of prepared samples were analyzed in detail. Under the 405 nm excitation, Ca 2 MgTeO 6 :Sm3+ phosphors showed four sharp emission peaks ascribed to the 4 f -4 f transitions, and the strongest one was at 645 nm. The best doping concentration of Sm3+ in Ca 2 MgTeO 6 :Sm3+ phosphors was 0.05 mol. The critical distance of the energy transfer between the Sm3+ ions was calculated to be 16.4 Å. The luminescence quenching was confirmed by the dipole-dipole interaction of among Sm3+ ions. The phosphor exhibited excellent thermal stability with high activation energy (0.32 eV). The commission international de l'Eclairage (CIE) chromaticity coordinates of Ca 2 MgTeO 6 :Sm3+ phosphors were in the orange-red region. The fabricated white light-emitting diode (w-LED) presented high color rendering index (R a) of 90 and a good correlated color temperature (CCT) of 6726 K. Thus, Ca 2 MgTeO 6 :Sm3+ phosphors have great potential applications in displays and photonic devices. • Ca 2 MgTeO 6: Sm3+ phosphors were firstly synthesized via high-temperature solid-state reaction. • The phosphor emits bright orange-red light at 405 nm excitation. • The phosphor possesses good color purity and excellent thermal stability. • The w-LED exhibits high color rending index. [ABSTRACT FROM AUTHOR]

A series of Eu3+-doped double perovskite Ca 2 MgTeO 6 (CMTO) red-emitting phosphors with high thermal stability were successfully prepared using the solid-state reaction at 1100 °C. The phase purity, surface morphology, and elemental mapping were investigated. Under near-ultraviolet (n-UV) (398 nm) and blue light (465 nm) excitation, the phosphors showed the strongest emission peak at 616 nm belonging to 5D 0 →7F 2 transition. Besides, the ideal Eu3+ doping concentration was 0.30 mol. The major reason for the concentration quenching was the nearest neighbor ions interaction. More importantly, the CMTO:Eu3+ phosphors showed excellent thermal stability with a high value of activation energy (0.29 eV). The color purity of CMTO:0.30Eu3+ phosphor was up to 99.9% and the internal quantum efficiency (IQE) of CMTO:0.30Eu3+ was measured to be 53%. White light-emitting diodes (w-LEDs) based on the InGaN chip (λ = 398 nm) and GaN chip (λ = 465 nm) with high color rendering index (R a) and low correlated color temperature (CCT) have been fabricated. Hence, the double perovskite CMTO:Eu3+ red phosphors have potential applications in the illumination field. • Ca 2 MgTeO 6: Eu3+ phosphors can be successfully synthesized via solid-state reaction. • The phosphor emits bright red light at 398 nm and 465 nm excitation. • The phosphor shows excellent thermal stability with high activity energy. • The w-LEDs exhibit good color rending index and low correlated color temperature. [ABSTRACT FROM AUTHOR]

The novel orange-red-emitting CaY 0·5 Ta 0·5 O 3 : x Sm3+ phosphors (x = 0.01–0.30) with double perovskite structures are prepared by a solid-state reaction. X-ray diffraction (XRD) patterns, photoluminescence, thermal quenching mechanism, and decay curves of the phosphors are discussed. The CaY 0·5 Ta 0·5 O 3 :Sm3+ phosphor shows the orange-red emission (603 nm) under 407 nm excitation. The photoluminescence (PL) spectra of CaY 0·5 Ta 0·5 O 3 :Sm3+ phosphor are ascribed to the 4G 5/2 to 6H J (J = 5/2, 7/2, 9/2, and 11/2). The quenching concentration of CaY 0·5 Ta 0·5 O 3 :Sm3+ phosphor is approximately 2 mol%. The quenching temperature for CaY 0·5 Ta 0·5 O 3 :0.02Sm3+ is estimated more than 500 K, indicating the products have excellent thermal stability. The temperature-dependent luminescence intensity ratio (I 650 nm / I 603 nm) of CaY 0·5 Ta 0·5 O 3 :0.02Sm3+ phosphor is discussed. The electroluminescence (EL) spectrum of the packaged red LED is similar to the PL spectrum of CaY 0·5 Ta 0·5 O 3 :Sm3+ phosphor. The CIE coordinates of the packaged white LED are (0.307, 0.335), which approach the equal energy white light. Therefore, Sm3+-doped CaY 0·5 Ta 0·5 O 3 phosphors have a promising application in white light-emitting diodes. • CaY 0·5 Ta 0·5 O 3 :Sm3+ phosphors can be firstly synthesized via solid-state reaction. • The phosphor emits bright red light at 407 nm excitation. • The phosphor possesses excellent thermal stability. • The w-LEDs exhibit good color rending index and low correlated color temperature. [ABSTRACT FROM AUTHOR]

A series of luminescent Dy3+-doped Ca 2 YTaO 6 phosphors were synthesized via the high temperature solid-state method firstly. They were characterized by X-ray diffraction (XRD) pattern, photoluminescence spectra, thermal quenching, and decay curves. The phosphors could be excited by near UV light 353 nm and emitted the luminescence consisting of blue (484 nm), yellow (576 nm), and red (669 nm) peaks, respectively. Furthermore, with the doping concentration of Dy3+ changed from 0.003 to 0.20, the maximum photoluminescence intensity for the Ca 2 YTaO 6 : x Dy3+ phosphor was at x c = 0.05 mol. The corresponding critical transfer distance was around 17.20 Å and thermal quenching of Ca 2 YTaO 6 :0.05Dy3+ was over than 500 K. The color coordinates of all Ca 2 YTaO 6 :Dy3+ samples entered into the yellow-light region. The whited LED was fabricated from the yellow-emitting Ca 2 YTaO 6 :Dy3+ and blue-emitting BaMgAl 10 O 17 :Eu2+ phosphors with the near UV LED chip (385 nm). The above results presented the Ca 2 YTaO 6 :Dy3+ phosphor as a promising yellow-emitting candidate for white light emitting diodes (W-LEDs) applications. • Ca 2 YTaO 6 :Dy3+ phosphors have been firstly synthesized via solid-state reaction. • The phosphor emits bright yellow light at 353 nm excitation. • The phosphor possesses excellent thermal stability. • The W-LEDs exhibits good color rending index and low correlated color temperature. [ABSTRACT FROM AUTHOR]