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.     

A novel reddish‐orange phosphor,NaLi2PO4:Eu3+

A series of Eu³⁺‐activated NaLi₂PO₄ novel phosphors was synthesized by the solid‐state reaction method. The X‐ray diffraction (XRD) and photoluminescence (PL) properties of these phosphors were investigated at room temperature. The excitation spectra indicate that these phosphors can be effectively excited by near‐UV (370–410 nm) light. The emission spectra exhibit strong reddish‐orange performance, which is due to the ⁵D₀ → ⁷F_J transitions of Eu³⁺ ions. The orange emission from transition ⁵D₀ → ⁷F₁ is dominant over that of ⁵D₀ → ⁷F_2. The concentration quenching of Eu³⁺ was observed in NaLi₂PO₄:Eu³⁺ when the Eu concentration was at 1 mol%. The impact of doping Eu³⁺ and photoluminescence properties were investigated and we propose a feasible interpretation. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis and luminescence properties of CaSnO3:Bi3+ blue phosphor and the emission improvement by Li+ ion

CaSnO₃:Bi³⁺ blue‐emitting phosphor was synthesized using a high‐temperature solid‐state reaction method in air. The crystal structures and luminescence properties were investigated. A broad emission band peaking at ~448 nm upon excitation at 262 and 308 nm was observed in the range 330–680 nm at room temperature due to ³P₁ → ¹S₀ transition of the Bi³⁺ ion. The chromaticity coordinate was (0.1786, 0.1665). The optimal Bi³⁺ ion concentration was ~0.6 mol% in CaSnO₃:Bi³⁺ phosphor. The emission spectrum of CaSnO₃:Bi³⁺ phosphor showed a blue‐shift with increasing temperature from 50 to 300 K due to the influence of temperature on the electron transition of the Bi³⁺ ion. The emission intensity of CaSnO₃:Bi³⁺ phosphor may be increased ~1.45 times by co‐doping Li⁺ ions as a charge compensator and fluxing agent. The luminescence mechanism is explained by a configurational coordinate diagram of Bi³⁺ ion in CaSnO₃:Bi³⁺ phosphor.     

Luminescence and energy transfer in Ce3+, Mn2+‐doped K2AEP2O7 (AE = Ca,Sr) phosphor

Pyrophosphates K₂AEP₂O₇ (AE = Ca, Sr) prepared by the classical solid‐state technique and activated with Ce³⁺ are described. Intense emission was observed in K₂AEP₂O₇ (AE = Ca, Sr). The effect of Mn²⁺ co‐doping was studied. The broad emission peak of Mn²⁺ was observed at 534 nm in K₂SrP₂O₇:Ce³⁺ and at 539 nm in K₂CaP₂O₇:Ce³⁺, Mn²⁺. Mn²⁺ emission was greatly enhanced by addition of the sensitizer Ce³⁺ due to efficient energy transfer from Ce³⁺ to Mn²⁺. Copyright © 2015 John Wiley & Sons, Ltd.     

Cation‐tunable blue phosphor Ca2PO4Cl:Eu2+: enhancive emission and site occupancy

A series of blue phosphors Ca_1.98–xM_xPO₄Cl:0.02Eu²⁺ (M = Mg and Sr) with different values of x were synthesized using a high‐temperature solid‐state reaction. X‐Ray diffraction and photoluminescence measurements were used to study the phase structure and luminescence properties. Ca₂PO₄Cl:0.02Eu²⁺ exhibits a tunable emission intensity and color due to the incorporation of Sr²⁺ or Mg²⁺. The incorporation of Sr²⁺ reduces the luminescence intensity and results in a slight red shift in the emission band. The incorporation of Mg²⁺ results in enhanced emission and a clear blue shift in the emission band along with a tunable chromatic coordination. Under excitation at λ = 334 nm, the emission intensity of the Mg²⁺‐doped Ca₂PO₄Cl:0.02Eu²⁺ is found to be 250% that of Ca₂PO₄Cl:0.02Eu²⁺. The luminescence behaviors of the as‐synthesized phosphors are discussed according to the host crystal structure and site occupancy of Eu²⁺. The results indicate that Mg²⁺‐doped Ca₂PO₄Cl:Eu²⁺ is more applicable as a near‐UV‐convertible blue phosphor for white light‐emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd.     

A novel red phosphor Ca2YNbO6:Eu3+ for WLEDs

Due to the advantages of good physicochemical properties, thermal stability, and optical properties, double perovskite compounds have received extensive attention. On this basis, a new type of red phosphor, Ca₂YNbO₆:xEu³⁺, was synthesized using a high-temperature solid-phase method. Its phase purity, morphology, elemental composition, absorption spectrum, photoluminescence, thermal stability, and Commission Internationale de l'éclairage (CIE) chromaticity coordinates were thoroughly investigated. The results display that there is no impurity phase in the samples and the convergence factor R_wp = 14.2%; the microscopic particles are uniform and full, and the distribution of each element is uniform. The energy band gap ΔE is between 3.71 eV and 3.65 eV. The luminescence intensity is the best when the doped Eu³⁺ concentration x reaches 0.4, and emits 612 nm red light (⁵D₀→⁷F₂) under 465 nm excitation, and the concentration quenching is attributed to a d–d interaction. The luminescence intensity at 425 K was still 75% of the room temperature luminescence intensity, which indicates that the thermal stability is extremely superior. The CIE chromaticity coordinates (0.6534, 0.3455) of the Ca2YNbO6:0.4Eu³⁺ phosphors are very close to National Television Standards Committee (0.670, 0.330), and the samples have low correlated colour temperature (2656 K) and high colour purity (99.90%). All findings suggest that Ca₂YNbO₆:Eu³⁺ can serve as a substitute for red phosphor in WLEDs.     

Luminescence in Li2Sr2Al2PO4F9:Dy3+ ‐ a novel nanophosphor

Earlier research has revealed numerous advantages of the wet chemical method in reaction acceleration, yield improvement, enhanced photoluminescence properties and the evolution of new material phases. In the present study the novel nanophosphor Li₂Sr₂Al₂PO₄F₉:Dy³⁺ was synthesized by a one‐step wet chemical method. Formation of single‐phase compounds was confirmed by X‐ray diffraction (XRD) and characterized by photoluminescence (PL) and transmission electron microscopy (TEM) techniques. The average diameter of the particles was calculated from the TEM image as ca. 20 nm. The synthesized nanophosphor exhibited intense blue and yellow emissions at 482 and 575 nm, respectively, owing to the Dy³⁺ ion, by Hg‐free excitation at 387 nm, i.e. solid‐state lighting excitation. The results obtained showed that phosphors have the potential for applications in the lamp industry. Copyright © 2011 John Wiley & Sons, Ltd.     

Redox luminescence switch based on Mn2+‐doped NaYF4:Yb,Er upconversion nanorods

An redox luminescence switch was developed for the sensing of glutathione (GSH), l ‐cysteine (Cys) or l ‐ascorbic acid (AA) based on redox reaction. The Mn²⁺‐doped NaYF₄:Yb,Er upconversion nanorods (UCNRs) with an emission peak located in the red region were synthesized. The luminescence intensity of the UCNRs could be quenched due to the Mn²⁺ could be oxidized to MnO₂ by KMnO₄. Subsequently, when the AA, GSH or Cys was added into the MnO₂ modified upconversion nanosystem, which could reduced MnO₂ to Mn²⁺ and the luminescence intensity was recovered. The concentration ranges of the nanosystem are 0.500–3.375 mM (R² = 0.99) for AA, 0.6250–11.88 mM (R² = 0.99) for GSH and 0.6250–9.375 mM (R² = 0.99) for Cys, respectively.     

Synthesis and luminescent properties of novel BaGd2O4:Eu3+ scintillating phosphor

BaGd_2‐xO₄:xEu³⁺ and Ba_1‐yGd_1.79‐2yEu_0.21Na_3yO₄ phosphors were synthesized at 1300°C in air by conventional solid‐state reaction method. Phosphors were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence excitation (PLE) spectra, photoluminescence (PL) spectra and thermoluminescence (TL) spectra. Optimal PL intensity for BaGd_2‐xO₄:xEu³⁺ and Ba_1‐yGd_1.79‐2yEu_0.21Na_3yO₄ phosphors at 276 nm excitation were found to be x = 0.24 and y = 0.125, respectively. The PL intensity of Eu³⁺ emission could only be enhanced by 1.3 times with incorporation of Na⁺ into the BaGd₂O₄ host. Enhanced luminescence was attributed to the flux effect of Na⁺ ions. However, when BaGd₂O₄:Eu³⁺ phosphors were codoped with Na⁺ ions, the induced defects confirmed by TL spectra impaired the emission intensity of Eu³⁺ ions. Copyright © 2012 John Wiley & Sons, Ltd.     

Phosphors Ba2LaTaO6:Mn4+ and its alkali metal charge compensation for plant growth illumination

A series of Mn⁴⁺-doped and Mn⁴⁺,K⁺-co-doped Ba₂LaTaO₆ (BLT) double-perovskite phosphors was synthesized using a high-temperature solid-state reaction. The phase purity and luminescence properties were also studied. The optimum doping concentration of Mn⁴⁺ and K⁺ was obtained by investigating the photoluminescence excitation spectra and photoluminescence emission spectra. The comparison of BLT:Mn⁴⁺ phosphors with and without K⁺ ions shows that the photoluminescence intensity of K⁺-doped phosphors was greatly enhanced. This is because there was a charge difference when Mn⁴⁺ ions were doped with Ta⁵⁺ ions in BLT. Mn⁴⁺–K⁺ ion pairs were formed after doping K⁺ ions, which hinders the nonradiative energy transfer between Mn⁴⁺ ions. Therefore, the luminescence intensity, quantum yield, and thermal stability of phosphors were enhanced. The electroluminescence spectra of BLT:Mn⁴⁺ and BLT:Mn⁴⁺,K⁺ were measured. The spectra showed that the light emitted from the phosphors corresponded well with chlorophyll a and phytochrome P_R. The results show that the BLT:Mn⁴⁺,K⁺ phosphors had good luminescence properties and application prospects and are ideal materials for plant-illuminated red phosphors.     

Synthesis and luminescence properties of a novel blue emitting phosphor NaMgPO4:Eu2+

A novel blue‐emitting phosphor of Eu²⁺‐activated NaMgPO₄ was prepared by combustion‐assisted synthesis. Sodium dihydrogen phosphate and magnesium nitrate were used as the source of Na, P and Mg, respectively. The ratios of magnesium and phosphorus components that were dissolved into the combustion solution were changed from 1:1 to 1:1.3. Their effect on the crystallinities and photoluminescence spectra of the phosphor particles were investigated. The post‐heated phosphor particles had a broad excitation wavelength that ranged from 240 to 410 nm. The phosphor particles prepared from the combustion solution with a 1:1.2 ratio of magnesium to phosphorus had maximum emission intensity under ultraviolet excitation. The effect of doped Eu²⁺ concentration on the emission intensity of NaMgPO₄:Eu²⁺ was also investigated.     

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.     

Dual substitution of host lattice ions to enhance the luminescence properties of Zn2TiO4:Cr3+ phosphor

Near-infrared light sources have potential applications in many fields. Cr³⁺ is a good luminescence centre to prepare near-infrared phosphors. Improving the performance of existing near-infrared luminescent materials has indeed attracted great interest from researchers. The luminescence properties of Zn₂TiO₄:Cr³⁺ were improved by crystal field engineering strategies. Zn²⁺–Ti⁴⁺ was partially replaced using a Li⁺–Nb⁵⁺ ion pair based on the Zn₂TiO₄:Cr³⁺ phosphors. Luminescence Cr³⁺-activated luminescent materials are sensitive to changes in the local crystal structure and crystal field environment. Doping of Li⁺–Nb⁵⁺ increased the luminescence intensity up to 2.7 times that of the undoped sample. Also, the thermal stability of the phosphor was greatly increased by the replacement of Li⁺–Nb⁵⁺.     

Luminescent properties of novel red‐emitting M7Sn(PO4)6:Eu3+ (M = Sr,Ba) for light‐emitting diodes

Novel red‐emitting phosphors, Eu³⁺‐activated M₇Sn(PO₄)₆ (M = Sr, Ba), were synthesized at 1200°C by conventional solid‐state reaction method. The luminescent properties of M₇Sn(PO₄)₆:Eu³⁺ (M = Sr, Ba) phosphors were investigated, and the critical concentration of the activator (Eu³⁺) concentration were found to be 0.175 mol and 0.21 mol per formula unit for Sr_7‐xSn(PO₄)₆:xEu³⁺ and Ba_7‐xSn(PO₄)₆:xEu³⁺, respectively. These phosphors presented red luminescence under the excitation of 395 or 465 nm, perfectly matching with the emissions wavelength of near‐ultraviolet (UV) light‐emitting diodes (LEDs) and InGaN blue LED.     

Solid‐state synthesis and luminescent properties of yellow‐emitting phosphor NaY(MoO4)2:Dy3+ for white light‐emitting diodes

A yellow‐emitting phosphor NaY(MoO₄)₂:Dy³⁺ was synthesized using a solid‐state reaction at 550 °C for 4 h, and its luminescent properties were investigated. Its phase formation was studied using X‐ray powder diffraction analysis, and there were no crystalline phases other than NaY(MoO₄)₂. NaY(MoO₄)₂:Dy³⁺ produced yellow emission under 386 or 453 nm excitation, and the prominent luminescence was yellow (575 nm) due to the ⁴ F_9/2→⁶H_13/2 transition of Dy³⁺. For the 575 nm emission, the excitation spectrum had one broad band and some narrow peaks; the peaks were located at 290, 351, 365, 386, 426, 453 and 474 nm. Emission intensities were influenced by the Dy³⁺ doping content and a concentration quenching effect was observed; the phenomenon was also proved by the decay curves. Moreover, the Commission International de I'Eclairage chromaticity coordinates of NaY(MoO₄)₂:Dy³⁺ showed similar values at different Dy³⁺ concentrations, and were located in the yellow region. Copyright © 2015 John Wiley & Sons, Ltd.     

Sol–gel synthesis,characterization and luminescence properties of SrMgAl2SiO7:Eu2+ as a novel nanocrystalline phosphor

In this research, a new SrMgAl₂SiO₇:Eu²⁺ phosphor was synthesized via the sol–gel method. The phase‐forming processes were studied by thermogravimetric–differential thermal analysis and X‐ray diffraction technique. Scanning electron microscopy showed that there is uniform morphology and microstructure owing to the sol–gel route. Spectrophotometry and colorimetry analyses illustrated that, under short ultraviolet excitation, the main emission peak occurred at 421 nm and also a relatively pure blue color was observed that was ascribed to the 4f⁶5d¹(²D) → 4f⁷(⁸S_7/2) transition of Eu²⁺ with color coordination of x = 0.187, y = 0.077. Finally, it was found that the color and phase purity of the synthesized powder increased as calcinations time increased. Copyright © 2010 John Wiley & Sons, Ltd.     

Crystal structure and luminescence properties of the blue‐green‐emitting Ba9(Lu,Y)2Si6O24:Ce3+ phosphor

Samples of the Ba₉(Lu_2‐xY_x)Si₆O₂₄:Ce³⁺ (x = 0–2) blue‐green phosphors were synthesized by solid‐state reactions. All the samples exhibited a rhombohedral crystal structure. As the Y³⁺ concentration increased, the diffraction peaks shifted to the small angle region and the lattice parameters increased due to the larger ionic radius of Y³⁺ (r = 0.900 Å) compared with that of Lu³⁺ (r = 0.861 Å). Under 400 nm excitation, samples exhibited strong blue‐green emissions around 490 nm. The emission bands had a slight blue shift that resulted from weak crystal‐field splitting with increasing Y³⁺ concentration. Luminescence intensity and quantum efficiency (QE) decreased with increasing Y³⁺ concentration. The internal QE decreased from 74 to 50% and the external QE decreased from 50 to 34% as x increased from 0 to 2. The thermal stability of the Lu series was better than that of the Y‐series. The excitation band peak around 400 nm matched well with the emission light from the efficient near‐ultraviolet (NUV) chip. These results indicate promising applications for these NUV‐based white light‐emitting diodes.     

Dual emission of Ce3+,Mn2+‐coactivated Ca3YNa(PO4)3F via energy transfer: a single component white/yellow‐emitting phosphor

A series of Ce³⁺,Mn²⁺‐coactivated Ca₃YNa(PO₄)₃F phosphors were synthesized via a traditional solid‐state reaction under a reductive atmosphere. X‐Ray powder diffraction was used to confirm that the crystal structure and diffraction peaks of Ce³⁺/Mn²⁺‐doped samples matched well with the standard data. A spectral overlap between the emission band of Ce³⁺ and the excitation band of Mn²⁺ suggested the occurrence of energy transfer from Ce³⁺ to Mn²⁺. With increasing Mn²⁺ content, the emission intensities and lifetime values of the Ce³⁺ emission for Ca₃YNa(PO₄)₃F:Ce³⁺,Mn²⁺ phosphors linearly decrease, whereas the energy transfer efficiencies gradually increase to 89.35%. By adjusting the relative concentrations of Ce³⁺ and Mn²⁺, the emission hues are tuned from blue to white and eventually to yellow. These results suggest that Ca₃YNa(PO₄)₃F:Ce³⁺,Mn²⁺ phosphors have promising application as white‐emitting phosphors for near‐ultraviolet light‐emitting diodes.     

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.     

Characterization and luminescence properties of CaMgSi2O6:Eu2+ blue phosphor

A blue CaMgSi₂O₆:Eu²⁺ phosphor was prepared by the solid‐state reaction method and the phosphor characterized in terms of crystal structure, particle size, photoluminescence (PL), thermoluminescence (TL) and mechanoluminescence (ML) properties using X‐ray diffraction (XRD), transmission electron microscopy (TEM), PL spectroscopy, TLD reader and ML impact technique. The XRD result shows that phosphor is formed in a single phase and has a monoclinic structure with the space group C2/c. Furthermore, the PL excitation spectra of Eu²⁺‐doped CaMgSi₂O₆ phosphor showed a strong band peak at 356 nm and the PL emission spectrum has a peak at 450 nm. The depths and frequency factors of trap centers were calculated using the TL glow curve by deconvolution method in which the trap depths were found to be 0.48 and 0.61 eV. The formation of CaMgSi₂O₆:Eu²⁺ phosphor was confirmed by Fourier transform infrared spectroscopy. The ML intensity increased linearly with the impact velocity of the piston used to deform the phosphor. It was shown that the local piezoelectricity‐induced electron bombardment model is responsible for the ML emission. Finally, the optical properties of CaMgSi₂O₆:Eu²⁺ phosphors are discussed. Copyright © 2015 John Wiley & Sons, Ltd.