A novel red emitting phosphor LiBaB9O15:Sm2+/Sm3+, li+ with broad excitation band for white LEDs

A novel tunable red emitting phosphor LiBaB₉O₁₅:Sm²⁺/Sm³⁺, Li⁺ with broad excitation band was synthesized by a high temperature solid‐state method. Luminescence properties were investigated in detail by luminescence, X‐ray photoelectron spectroscopy (XPS) spectra and CIE chromaticity coordinates. XPS data confirmed that there were Sm³⁺ in LiBaB₉O₁₅:Sm³⁺ and Sm²⁺/Sm³⁺ in LiBaB₉O₁₅:Sm²⁺/Sm³⁺, respectively. Spectral property of LiBaB₉O₁₅:Sm³⁺, LiBaB₉O₁₅:Sm³⁺/Sm²⁺ and LiBaB₉O₁₅:Sm²⁺, Li⁺ presented that the excitation band of Sm³⁺ widened and the excitation band of Sm²⁺ ranged from 350 to 450 nm. And the red light color is tunable with changing Li⁺ concentration. The results indicated that LiBaB₉O₁₅:Sm²⁺/Sm³⁺, Li⁺ may be promising red phosphor for white light emitting diodes.     

Synthesis and photoluminescence characteristics of Sm3+‐doped Bi4Si3O12 red‐emitting phosphor

A series of novel red‐emitting Sm³⁺‐doped bismuth silicate phosphors, Bi₄Si₃O₁₂:xSm³⁺ (0.01 ≤ x ≤ 0.06), were prepared via the sol–gel route. The phase of the synthesized samples calcinated at 800 °C is isostructural with Bi₄Si₃O₁₂ according to X‐ray diffraction results. Under excitation with 405 nm light, some typical peaks of Sm³⁺ ions centered at 566, 609, 655 and 715 nm are found in the emission spectra of the Sm³⁺‐doped Bi₄Si₃O₁₂ phosphors. The strongest peak located at 609 nm is due to ⁴G_5/2–⁶H_7/2 transition of Sm³⁺. The luminescence intensity reaches its maximum value when the Sm³⁺ ion content is 4 mol%. The results suggest that Bi₄Si₃O₁₂:Sm³⁺ may be a potential red phosphor for white light‐emitting diodes. Copyright © 2016 John Wiley & Sons, Ltd.     

Combustion synthesis and luminescence properties of SrAl2O4:Eu2+, Dy3+, Tb3+ phosphor.

Eu(2+), Dy(3+) and Tb(3+) co-doped strontium aluminate phosphor with high brightness and long afterglow was synthesized by a combustion method, using urea as a reducer. The properties of SrAl(2)O(4):Eu(2+),Dy(3+),Tb(3+) phosphor with a series of initiating combustion temperatures, urea concentrations and boric acid molar fractions were investigated. The sample at initiating combustion temperature of 600 degrees C exhibited an intense emission peak at 513 nm, in which the phosphor existed as a single-phase monoclinic structure. The experimental results showed that the optimum ratio of urea is 2.0 times higher than theoretical quantities and that the suitable molar fraction of H(3)BO(3) is 0.08. The average particle size of the phosphor was 50-80 nm and its luminescence properties were studied systematically. Compared with SrAl(2)O(4):Eu(2+),Dy(3+) phosphor, the initial luminescence brightness improved from 2.50 candela (cd)/m(2) to 3.55 cd/m(2) and the long afterglow time was prolonged from 1290 s to 2743 s.     

Synthesis and luminescence properties of blue‐emitting phosphor Ca12Al14O32F2:Eu2+ for white light‐emitting diode

A blue‐emitting phosphor Ca₁₂Al₁₄O₃₂F₂:Eu²⁺ was synthesized using a high‐temperature solid‐state reaction under a reductive atmosphere. The X‐ray diffraction measurements indicate that a pure phase Ca₁₂Al₁₄O₃₂F₂:Eu²⁺ can be obtained for low doping concentration of Eu²⁺. The phosphor has a strong absorption in the range 270–420 nm with a maximum at ~340 nm and blue emission in the range 400–500 nm with chromatic coordination of (0.152, 0.045). The optimal doping concentration is ~0.24. In addition, the luminescence properties of the as‐synthesized phosphor were evaluated by comparison with those of Ca₁₂Al₁₄O₃₂Cl₂:Eu²⁺ and the commercially available phosphor BaMgAl₁₀O₁₇:Eu²⁺. The emission intensity of Ca₁₂Al₁₄O₃₂F₂:Eu²⁺ was ~72% that of BaMgAl₁₀O₁₇:Eu²⁺ under excitation at λ = 375 nm. The results indicate that Ca₁₂Al₁₄O₃₂F₂:Eu²⁺ has potential application as a near‐UV‐convertible blue phosphor for white light‐emitting diodes.     

Pure red upconverted and near-infrared luminescence properties of Er3+-doped SnO2 nanocrystals for lighting applications

Tin oxide (SnO₂) nanocrystalline powders doped with erbium ion (Er³⁺) in different molar ratios (0, 3, 5, and 7 mol%) were prepared using a solid-state reaction technique. These samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible absorption, visible upconversion, and near-infrared luminescence techniques. XRD analysis revealed the tetragonal rutile structure of SnO₂ and the average crystallite size was about 32 nm. From Tauc's plots, it was confirmed that the substitution of Er³⁺ ions into the SnO₂ host lattice resulted in the narrowing its band gap. Optical absorption bands at 520 and 654 nm correspond to the 4f electron transitions of Er³⁺ further confirming visible light absorption. Infrared luminescence spectra showed a broad band centred at 1536 nm which is assigned to the ⁴I_13/2 → ⁴I_15/2 transition of Er³⁺. Visible upconverted emission spectra under 980 nm excitation exhibit a strong red luminescence with a main peak at 672 nm which is attributed to the ⁴F_9/2 → ⁴I_15/2 transition of Er³⁺. Power-dependent upconversion spectra confirmed that two photons participated in the upconversion mechanism. Enhancement in the intensities of both visible and infrared luminescence was observed when raising the concentration. The results pave the way for the potential applications of these nanocrystalline powders in energy harvesting applications such as infrared light upconverting layer in solar cells, light emitting diodes, infrared broadband sources and amplifiers, and biological labelling.     

Optical characterization and the energy level scheme for Ce3+‐doped BaY2Si3O10 blue‐emitting phosphor

A series of Ce³⁺‐activated blue‐emitting phosphors BaY₂Si₃O₁₀ (BYSO) was designed and synthesized by a conventional solid‐state method. Upon ultraviolet light (250–370 nm) excitation, the obtained phosphors showed an intense blue emission band centered at 400–427 nm depending on doping concentration, and corresponding to the 5d→4f transition of Ce³⁺. The effects of doping concentration on crystal structure, emitting color, photoluminescence and photoluminescence excitation spectra, as well as the concentration quenching mechanism were studied in detail. The optimal doping concentration of Ce³⁺ in this phosphor was demonstrated to be about 0.75% and the concentration quenching mechanism can be ascribed to electric dipole–dipole interactions with a critical distance of ~38 Å. These fine luminescence properties indicate that BYSO:Ce³⁺ may be a potential blue phosphor for full‐color ultra‐violet (UV) white light emitting diodes (WLEDs).     

Photoluminescence properties of a new orange–red‐emitting Sm3+–La3SbO7 phosphor

The antimonate compound La₃SbO₇ has high chemical stability, lattice stiffness and thermal stability. Orange–red‐emitting antimonate‐based phosphors La₃SbO₇:xSm³⁺ (x = 0.02, 0.05, 0.08, 0.10, 0.15, 0.20 and 0.25) were synthesized. The phase structure and photoluminescence properties of these phosphors were investigated. The emission spectrum obtained on excitation at 407 nm contained exclusively the characteristic emissions of Sm³⁺ at 568, 608, 654 and 716 nm, which correspond to the transitions from ⁴G_5/2 to ⁶H_5/2, ⁶H_7/2, ⁶H_9/2 and ⁶H_11/2 of Sm³⁺, respectively. The strongest emission was located at 608 nm due to the ⁴G_5/2→⁶H_7/2 transition of Sm³⁺, generating bright orange–red light. The critical quenching concentration of Sm³⁺ in La₃SbO₇:Sm³⁺ phosphor was determined as 10% and the energy transfer between Sm³⁺ was found to be through an exchange interaction. The International Commission on Illumination chromaticity coordinates of the La₃SbO₇:0.10Sm³⁺ phosphors are located in the orange–red region. The La₃SbO₇:Sm³⁺ phosphors may be potentially used as red phosphors for white light‐emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and characterization of Ba3Si6O12N2:Eu2+ phosphor

Eu²⁺‐doped Ba₃Si₆O₁₂N₂ phosphors were prepared successfully via a modified solid‐state diffusion method. The phosphors were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence measurements. These phosphors were effectively excited at 355 nm and an intense emission peaking in the range 480 nm to 525 nm in the blue region was observed. The optimized dopant concentration was determined to be 1 mol% of Eu²⁺ ion. The colour coordinates for phosphor were found to be (0.196, 0.326) in the blue region. This phosphor may find application for near‐ultraviolet (NUV) excited lamp phosphors. The thermoluminescence study shows the complex glow curve. Trapping parameters (activation energy and frequency factor) were calculated for individual deconvoluted peaks by Chen's peak shape method, the initial rise method and the whole glow peak method. Copyright © 2015 John Wiley & Sons, Ltd.     

Photoluminescence properties of a novel phosphor CaB2O4:Eu3+ under NUV excitation

The new borate phosphor CaB₂O₄:Eu³⁺ was synthesized by solid‐state method and their photoluminescence properties were investigated. The results show that the pure phase of CaB₂O₄ could be available at 900°C, CaB₂O₄:Eu³⁺ phosphor could be effectively excited by the near ultraviolet light (NUV) (392 nm), and the luminescent intensity of CaB₂O₄:Eu³⁺ phosphor reached to the highest when the doped‐Eu³⁺ content was 4 mol%. The emission spectra of CaB₂O₄:Eu³⁺ phosphor could exhibit red emission at 612 nm and orange emission at 588 nm, which are ascribed to the ⁵D₀–⁷F₂ and ⁵D₀–⁷F₁ transitions of Eu³⁺ ions. Copyright © 2009 John Wiley & Sons, Ltd.     

Emission analysis of Tb3+‐and Sm3+‐ion‐doped (Li2O/Na2O/K2O) and (Li2O + Na2O/Li2O + K2O/K2O + Na2O)‐modified borosilicate glasses

Four series of borosilicate glasses modified by alkali oxides and doped with Tb³⁺ and Sm³⁺ ions were prepared using the conventional melt quenching technique, with the chemical composition 74.5B₂O₃ + 10SiO₂ + 5MgO + R + 0.5(Tb₂O₃/Sm₂O₃) [where R = 10(Li₂O /Na₂O/K₂O) for series A and C, and R = 5(Li₂O + Na₂O/Li₂O + K₂O/K₂O + Na₂O) for series B and D]. The X‐ray diffraction (XRD) patterns of all the prepared glasses indicate their amorphous nature. The spectroscopic properties of the prepared glasses were studied by optical absorption analysis, photoluminescence excitation (PLE) and photoluminescence (PL) analysis. A green emission corresponding to the ⁵D₄ → ⁷F₅ (543 nm) transition of the Tb³⁺ ions was registered under excitation at 379 nm for series A and B glasses. The emission spectra of the Sm³⁺ ions with the series C and D glasses showed strong reddish‐orange emission at 600 nm (⁴G_5/2 →⁶H_7/2) with an excitation wavelength λ_exci = 404 nm (⁶H_5/2→⁴F_7/2). Furthermore, the change in the luminescence intensity with the addition of an alkali oxide and combinations of these alkali oxides to borosilicate glasses doped with Tb³⁺ and Sm³⁺ ions was studied to optimize the potential alkali‐oxide‐modified borosilicate glass.     

Photoluminescence and thermoluminescence studies of CaAl2O4:Dy3+ phosphor

Calcium aluminate phosphors activated by Dy³⁺ have been prepared by a combustion method at a temperature of 600°C. Photoluminescence (PL) and thermoluminescence (TL) properties of gamma‐irradiated Dy‐doped calcium aluminate were investigated. The PL spectrum shows a broad peak around 488 nm and 573 nm, under 347 nm excitation. Thermoluminescence studies were performed for different concentrations of Dy. Optimum intensity of photoluminescence was found for 0.02 mol% concentration of Dy. It was found that initially the peak TL intensity increases with increasing concentration of Dy in the CaAl₂O₄ host, attains a maximum value for 0.05 mol% concentration and decreases with further increase in the doping concentration due to concentration quenching. Copyright © 2015 John Wiley & Sons, Ltd.     

Structural characterization and optical properties of Ca2MgSi2O7:Eu2+,Dy3+ phosphor by solid‐state reaction method

Ca₂MgSi₂O₇:Eu²⁺,Dy³⁺ phosphor was prepared by the solid‐state reaction method under a weak reducing atmosphere. The obtained phosphor was characterized using X‐ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy dispersive X‐ray spectroscopy (EDX) and Fourier transform infrared (FT‐IR) techniques. The phase structure of the Ca₂MgSi₂O₇:Eu²⁺,Dy³⁺ phosphor was akermanite type, which is a member of the melilite group. The surface morphology of the sintered phosphor was not uniform and phosphors aggregated tightly. EDX and FT‐IR spectra confirm the elements present in the Ca₂MgSi₂O₇:Eu²⁺,Dy³⁺ phosphor. Under UV excitation, a broadband emission spectrum was found. The emission spectra observed in the green region centered at 535 nm, which is due to the 4f–5d transition. The mechanoluminescence (ML) intensity of the prepared phosphor increased linearly with increases in the mechanical load. The ML spectra were similar to the photoluminescence (PL), which indicates that ML is emitted from the same emitting center of Eu²⁺ ions as PL. Copyright © 2014 John Wiley & Sons, Ltd.     

Luminescence of Sm3+ in double perovskite-type Ba2SrWO6 for insect trapping

The predominant method for pest control has been the use of pesticides, which have been shown to have detrimental effects on soil, freshwater, and crop quality. Therefore, the development of novel and sustainable crop protection strategies has become increasingly imperative. In this study, a novel orange–red emitting Ba₂SrWO₆: Sm³⁺ phosphor was synthesized using the high-temperature solid-state reaction. Under ultraviolet excitation, the phosphors showed obvious emission peaks at 575, 614, and 662 nm. The Ba₂SrWO₆: Sm³⁺ was used to fabricate a fluorescence film with polydimethylsiloxane (PDMS), and attracted twice as many insects as the blank control group under 365 nm ultraviolet light. This material holds great potential as a fluorescent agent for insect trapping in the pest control fields of tea, cotton, eggplant, rice, potato, grape, and other agricultural industries. Our findings provide an eco-friendly approach to pest management for the increment of food production.     

Influence of Er3+ concentration on the photoluminescence characteristics and excitation mechanism of Gd2O3:Er3+ phosphor synthesized via a solid‐state reaction method

An Er³⁺‐doped phosphor of Gd₂O₃ (Gd₂O₃:Er³⁺) was prepared using a conventional solid‐state reaction method. The structure and particle size were determined from X‐ray powder diffraction measurements. The average particle size of the phosphor was in between 20 and 50 nm. The particle size and structure of the phosphor were further confirmed by transmission electron microscopy (TEM) analysis. Luminescence spectra were recorded under excitation wavelengths of 275, 380, 515 and 980 nm. The visible upconversion and downconversion luminescence spectra of the Gd₂O₃:Er³⁺ phosphor were investigated as a function of Er³⁺ ion concentration. The upconverted emission at 980 nm excitation shows enhanced red emission with respect to green emission as the dopant concentration increased. Similar results were observed for downconversion emission under 275 and 380 nm excitation wavelengths. The mechanisms responsible for populating the ⁴S_3/2 and ⁴ F_9/2 levels, for green and red emissions, respectively, are different for different excitations and for different concentrations of Er³⁺. Copyright © 2014 John Wiley & Sons, Ltd.     

Highly Reversible Na Storage in Na3V2(PO4)3 by Optimizing Nanostructure and Rational Surface Engineering

Sodium‐ion batteries (NIBs) have attracted more and more attention as economic alternatives for lithium‐ion batteries (LIBs). Sodium super ionic conductor (NASICON) structure materials, known for high conductivity and chemical diffusion coefficient of Na⁺ (≈10^?14 cm² s^?1), are promising electrode materials for NIBs. However, NASICON structure materials often suffer from low electrical conductivity (<10^?4 S cm^?1), which hinders their electrochemical performance. Here high performance sodium storage performance in Na₃V₂(PO₄)₃ (NVP) is realized by optimizing nanostructure and rational surface engineering. A N, B codoped carbon coated three‐dimensional (3D) flower‐like Na₃V₂(PO₄)₃ composite (NVP@C‐BN) is designed to enable fast ions/electrons transport, high‐surface controlled energy storage, long‐term structural integrity, and high‐rate cycling. The conductive 3D interconnected porous structure of NVP@C‐BN greatly releases mechanical stress from Na⁺ extraction/insertion. In addition, extrinsic defects and active sites introduced by the codoping heteroatoms (N, B) both enhance Na⁺ and e^? diffusion. The NVP@C‐BN displays excellent electrochemical performance as the cathode, delivering reversible capacity of 70% theoretical capacity at 100 C after 2000 cycles. When used as anode, the NVP@C‐BN also shows super long cycle life (38 mA h g^?1 at 20 C after 5000 cycles). The design provides a novel approach to open up possibilities for designing high‐power NIBs.     

Eu3+-activated red phosphor Ca3YAl3B4O15 with low thermal quenching behaviour

This paper reports a sequence of a Ca₃YAl₃B₄O₁₅:xEu³⁺ red phosphor prepared using a high-temperature solid-state reaction. At the excitation of 396 nm, the samples emitted intense red emission centred at ~623 nm, which could be attributed to the ⁵D₀→⁷F₂ transition of the Eu³⁺ ion. The results showed that the optimum Eu³⁺ doping concentration of Ca₃YAl₃B₄O₁₅:Eu³⁺ phosphor was x = 80 mol%, and the concentration quenching mechanism of Ca₃YAl₃B₄O₁₅:Eu³⁺ red phosphor belonged to the exchange coupling between Eu³⁺ ions. The Commission Internationale de l'éclairage (CIE) coordinates and colour purity of Ca₃Y_0.2Al₃B₄O₁₅:0.8Eu³⁺ were calculated as (0.6375, 0.3476) and 95.5%, respectively. Moreover, the red emission of the obtained phosphor Ca₃YAl₃B₄O₁₅:0.8Eu³⁺ exhibited a low thermal quenching behaviour with an intensity retention rate of 92.85% at 150°C. The above results manifest that the Eu³⁺-activated Ca₃YAl₃B₄O₁₅ phosphor is predicted to be a promising red luminescent component for white light-emitting diodes.     

Persistent luminescence of CaMgSi2O6:Eu2+,Dy3+ and CaMgSi2O6:Eu2+,Ce3+ phosphors prepared using the solid‐state reaction method

CaMgSi₂O₆:Eu²⁺,Dy³⁺ and CaMgSi₂O₆:Eu²⁺,Ce³⁺ phosphors were synthesized using the solid‐state reaction method. X‐Ray diffraction (XRD) and photoluminescence (PL) analyses were used to characterize the phosphors. The XRD results revealed that the synthesized CaMgSi₂O₆:Eu²⁺,Dy³⁺ and CaMgSi₂O₆:Eu²⁺,Ce³⁺ phosphors were crystalline and are assigned to the monoclinic structure with a space group C2/c. The calculated crystal sizes of CaMgSi₂O₆:Eu²⁺,Dy³⁺ and CaMgSi₂O₆:Eu²⁺,Ce³⁺ phosphors with a main (221) diffraction peak were 44.87 and 53.51 nm, respectively. Energy‐dispersive X‐ray spectroscopy (EDX) confirmed the proper preparation of the sample. The PL emission spectra of CaMgSi₂O₆:Eu²⁺,Dy³⁺ and CaMgSi₂O₆:Eu²⁺,Ce³⁺ phosphors have a broad band peak at 444.5 and 466 nm, respectively, which is due to electronic transition from 4f⁶5d¹ to 4f⁷. The afterglow results indicate that the CaMgSi₂O₆:Eu²⁺,Dy³⁺ phosphor has better persistence luminescence than the CaMgSi₂O₆:Eu²⁺,Ce³⁺ phosphor. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and luminescence characterization of a new yellowish‐orange phosphor: Ba2B10O17:Sm3+

A new yellowish‐orange emitting phosphor, Ba₂B₁₀O₁₇:Sm³⁺ for use as a white light‐emitting diode (W‐LED) was synthesized by a solid‐state reaction method. The X‐ray diffraction results indicated that a pure Ba₂B₁₀O₁₇ material was obtained. As a potential yellowish‐orange luminescent material for W‐LEDs, the Ba₂B₁₀O₁₇:Sm³⁺ phosphor could be excited effectively by near‐ultraviolet (n‐UV) light and exhibited yellowish‐orange emission centered at 560 nm corresponding to the ⁴G_5/2 → ⁶H_5/2 transition of Sm³⁺ ions. The optimum concentration of Sm³⁺ ions in Ba₂B₁₀O₁₇, critical transfer distance (Ra) and concentration quenching mechanism of the presented phosphor were investigated. Moreover, CIE chromaticity coordinates and color purity performance of the Ba₂B₁₀O₁₇:Sm³⁺ phosphor were also discussed. The present work suggests that the Ba₂B₁₀O₁₇:Sm³⁺ phosphor has potential as a type of yellowish‐orange emitting phosphor. Copyright © 2016 John Wiley & Sons, Ltd.     

Thermal quenching of luminescence of LiSr4(BO3)3:Eu2+ orange‐emitting phosphor

An orange‐emitting phosphor, Eu²⁺‐activated LiSr₄(BO₃)₃, was synthesized using the conventional solid‐state reaction. The photoluminescence excitation and emission spectra, and temperature dependence of the luminescence intensity of the phosphor were investigated. The results showed that LiSr₄(BO₃)₃:Eu²⁺ could be efficiently excited by incident light of 250–450 nm, and emits a strong orange light. With increasing temperature, the emission bands of LiSr₄(BO₃)₃:Eu²⁺ show an abnormal blue‐shift with broadening bandwidth and decreasing emission intensity. Copyright © 2013 John Wiley & Sons, Ltd.     

Molten salt synthesis and luminescence of Dy3+‐doped Y3Al5O12 phosphors

Dy³⁺‐doped Y₃Al₅O₁₂ phosphors were prepared at a relatively low temperature using molten salt synthesis. The phase of the prepared Dy³⁺‐doped Y₃Al₅O₁₂ phosphors was confirmed using X‐ray powder diffraction. Results indicated that Dy³⁺ doping did not change the Y₃Al₅O₁₂ phase. Following excitation at 352 nm, emission spectra of the Dy³⁺‐doped Y₃Al₅O₁₂ phosphors consisted of blue, yellow, and red emission bands. The influence of Dy³⁺ concentration and excitation wavelength on emission was investigated. The ratio of yellow light to blue light varied with change in Dy³⁺ doping concentration, due to changes in the structure around Dy³⁺. Emission intensities also changed when the excitation wavelength was changed. This variation is luminescence generated a system for tunable white light for Dy³⁺‐doped Y₃Al₅O₁₂ phosphors.