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.     

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.     

An efficient orange–red‐emitting LiNa3P2O7:Sm3+ pyrophosphate: Structural and optical analysis for solid‐state lighting

A trivalent rare‐earth ion (Sm³⁺)‐doped LiNa₃P₂O₇ (LNPO) phosphor was synthesized using a conventional high‐temperature solid‐state reaction route. A predominant orthorhombic phase of LNPO was observed in all X‐ray diffraction patterns. The surface states of the LNPO:Sm phosphor were confirmed by X‐ray photoelectron spectroscopy. Under 401 nm excitation, the Sm‐doped LNPO phosphors showed sharp emission peaks at 563, 600 and 647 nm that are related to the f–f transition of Sm³⁺ ions. The optimum concentration of Sm³⁺ (9 mol%) produced Commission Internationale de l'Eclairage chromaticity coordinates, color rendering index and correlated color temperature of (0.564, 0.434), 42 and 1843 K, respectively.     

Structural and luminescence properties of Sm3+‐doped bismuth phosphate glass for orange‐red photonic applications

In the present study, the effect of bismuth oxide (Bi₂O₃) content on the structural and optical properties of 0.5Sm³⁺‐doped phosphate glass and the effect of concentration on structural and optical properties of Sm³⁺‐doped bismuth phosphate (BiP) glass were studied. Structural characterization was accomplished using X‐ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy and ³¹P nuclear magnetic resonance (NMR) spectroscopy. Optical properties were studied using absorption, photoluminescence and decay measurements. Using optical absorption spectra, Judd–Ofelt parameters were derived to determine the local structure and bonding in the vicinity of Sm³⁺ ions. The emission spectra of Sm³⁺‐doped BiP glass showed two intense emission bands, ⁴G_5/2→⁶H_7/2 (orange) and ⁴G_5/2→⁶H_9/2 (red) for which the stimulated emission cross‐sections (σ_e) and branching ratios (β) were found to be higher. The quantum efficiencies were also calculated from decay measurements recorded for the ⁴G_5/2 level of Sm³⁺ ions. The suitable combination of Bi₂O₃ (10 mol%) and Sm³⁺ (0.5 mol%) ions in these glasses acted as an efficient lasing material and might be suitable for the development of visible orange‐red photonic materials.     

White‐ and blue‐light‐emitting dysprosium(III) and terbium(III)‐doped gadolinium titanate phosphors

Here we report the synthesis and structural, morphological, and photoluminescence analysis of white‐ and blue‐light‐emitting Dy³⁺‐ and Tm³⁺‐doped Gd₂Ti₂O₇ nanophosphors. Single‐phase cubic Gd₂Ti₂O₇ nanopowders consist of compact, dense aggregates of nanoparticles with an average size of ~25 nm for Dy³⁺‐doped and ~50 nm for Tm³⁺‐doped samples. The photoluminescence results indicated that ultraviolet (UV) light excitation of the Dy³⁺‐doped sample resulted in direct generation of white light, while a dominant yellow emission was obtained under blue‐light excitation. Intense blue light was obtained for Tm³⁺‐doped Gd₂Ti₂O₇ under UV excitation suggesting that this material could be used as a blue phosphor.     

The effects of charge compensation on photoluminescence properties of a new green‐emitting ZnB2O4:Tb3+ phosphor

Charge compensation is an effective way to eliminate charge defects and improve the luminescent intensity of phosphors. In this paper, a new green‐emitting phosphor ZnB₂O₄:Tb³⁺ was prepared by solid‐state reaction at 750°C. The effects of Tb³⁺ doping content and charge compensators (Li⁺, Na⁺ or K⁺) on photoluminescence properties of ZnB₂O₄:Tb³⁺ were investigated. X‐ray powder diffraction analysis confirms the sample has cubic structure of ZnB₂O₄. The excitation and emission spectra indicate that this phosphor can be excited by near ultraviolet light at 378 nm, and exhibits bright green emission with the highest peak at 544 nm corresponding to the ⁵D₄→⁷F₅ transition of Tb³⁺. The critical quenching concentration of Tb³⁺ in ZnB₂O₄ host is 8 mol%. The results of charge compensation show that the emission intensity can be improved by Na⁺ and K⁺. Specifically, K⁺ is the optimal one for ZnB₂O₄:Tb³⁺. Copyright © 2014 John Wiley & Sons, Ltd.     

Photoluminescence properties and energy transfer in Ce3+/Dy3+ co‐doped Sr3MgSi2O8 phosphors for potential application in ultraviolet white light‐emitting diodes

Sr₃MgSi₂O₈:Ce³⁺, Dy³⁺ phosphors were prepared by a solid‐state reaction technique and the photoluminescence properties were investigated. The emission spectra show not only a band due to Ce³⁺ ions (403 nm) but also as a band due to Dy³⁺ ions (480, 575 nm) (UV light excitation). The photoluminescence properties reveal that effective energy transfer occurs in Ce³⁺/Dy³⁺ co‐doped Sr₃MgSi₂O₈ phosphors, and the co‐doping of Ce³⁺ could enhance the emission intensity of Dy³⁺ to a certain extent by transferring its energy to Dy³⁺. The Ce³⁺/Dy³⁺ energy transfer was investigated by emission/excitation spectra, and photoluminescence decay behaviors. In Sr_2.94MgSi₂O₈:0.01Ce³⁺, 0.05Dy³⁺ phosphors, the fluorescence lifetime of Dy³⁺ (from 3.35 to 27.59 ns) is increased whereas that of Ce³⁺ is greatly decreased (from 43.59 to 13.55 ns), and this provides indirect evidence of the Ce³⁺ to Dy³⁺ energy transfer. The varied emitted color of Sr₃MgSi₂O₈:Ce³⁺, Dy³⁺ phosphors from blue to white were achieved by altering the concentration ratio of Ce³⁺ and Dy³⁺. These results indicate Sr₃MgSi₂O₈:Ce³⁺, Dy³⁺ may be as a candidate phosphor for white light‐emitting diodes. Copyright © 2012 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.     

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,cathodoluminescence and thermal stability of Sm3+‐activated Sr3La(VO4)3 red‐emitting phosphors

A series of Sm³⁺‐activated Sr₃La(VO₄)₃ phosphors were synthesized by a facile sol‐gel method. X‐ray diffraction patterns and photoluminescence (PL)/cathodoluminescence (CL) spectra as well as PL decay curves were employed to characterize the obtained samples. Upon 402 nm light excitation, the characteristic emissions of Sm³⁺ ions corresponding to ⁴G_5/2→⁶H_J transitions were observed in all the as‐prepared products. The PL emission intensity was increased with increase in Sm³⁺ ion concentration, while concentration quenching occurred when the doping concentration was over 4 mol%. The non‐radiative energy transfer mechanism for concentration quenching of Sm³⁺ ions was dominated by dipole–dipole interaction and the critical distance was around 21.59 Å. Furthermore, temperature‐dependent PL emission spectra revealed that the obtained phosphors possessed good thermal stability with an activation energy of 0.19 eV. In addition, the CL spectra of the samples were almost the same as the PL spectra, and the CL emission intensity showed a tendency to increase with increase in accelerating voltage and filament current. These results suggest that the Sm³⁺‐activated Sr₃La(VO₄)₃ phosphors with good color coordinates, high color purity and superior thermal stability may be a potential candidate for applications in white light‐emitting diodes and field‐emission displays as red‐emitting phosphors.     

Investigation of UV‐emitting Gd3+‐doped LiCaBO3 phosphor

Incorporating the Gd³⁺ rare earth ion in the LiCaBO₃ host lattice resulted in narrow‐band UV‐B emission peaking at 315 nm, with excitation at 274 nm. The LiCaBO₃:Gd³⁺ phosphor was synthesized via the solid‐state diffusion method. The structural, morphological and luminescence properties of this phosphor were characterized by X‐ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy. Electron paramagnetic resonance (EPR) characterization of the as‐prepared phosphors is also reported here. XRD studies confirmed the crystal formation and phase purity of the prepared phosphors. A series of different dopant concentrations was synthesized and the concentration‐quenching effect was studied. Critical energy transfer distance between activator ions was determined and the mechanism governing the concentration quenching is also reported in this paper. Copyright © 2015 John Wiley & Sons, Ltd.     

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.     

Tunable photoluminescence properties of Sr1‐yCayMoO4:Sm3+ phosphors (0 ≤ y < 1)

A series of Sr_1‐x‐yCa_yMoO₄:xSm³⁺ (0 ≤ x ≤ 7 mol% and 0 ≤ y < 1) phosphors was synthesized by a conventional solid‐state reaction method in air, and their structural and spectroscopic properties were investigated. The optimal doping concentration of Sm³⁺ in SrMoO₄:Sm³⁺ phosphor is 5 mol%. Under excitation with 275 nm, in Sr_1‐x‐yCa_yMoO₄:xSm³⁺ (0 ≤ x ≤ 7 mol% and 0 ≤ y < 1) phosphors, the emission band of the host was found to overlap with the excitation bands peaking at ~500 nm of Sm³⁺ ion, and the energy transfer from MoO₄^2? group to Sm³⁺ ion can also be observed. The International Commission on Illumination (CIE) chromaticity coordinates of Sr_0.95‐yCa_yMoO₄:0.05Sm³⁺ phosphors with excitation 275 nm varied systematically from an orange (0.4961, 0.3761) (y = 0) to a white color (0.33, 0.3442) (y = 0.95) with increasing calcium oxide (CaO) concentration. However, Sr_0.95‐yCa_yMoO₄:0.05Sm³⁺ phosphors with excitation at 404 nm only showed red emission and the energy transfer between MoO₄^2? group to Sm³⁺ ion was not observed. The complex mechanisms of luminescence and energy transfer are discussed by energy level diagrams of MoO₄^2? group and Sm³⁺ ion. Copyright © 2015 John Wiley & Sons, Ltd.     

Eu3+‐activated Y2MoO6: a narrow band red‐emitting phosphor with strong near‐UV absorption

Near‐UV excited narrow line red‐emitting phosphors, Eu³⁺‐activated Y₂MoO₆ systems, were synthesized using a simple molten salt reaction. The structure and photoluminescence characteristics were investigated using X‐ray powder diffraction, UV–Vis absorption and fluorescent spectrophotometry. The excitation spectra show strong broad‐band absorptions in the near‐UV to blue light regions which match the radiation of near‐UV light‐emitting diode chips well. Under excitation of either near‐UV or blue light, intense red emission with a main peak of 611 nm is observed, ascribed to the ⁵D₀–⁷F₂ transition of Eu³⁺ ions; the optimal doping concentration is 20 mol%. The chromaticity coordinates (x = 0.65, y = 0.34) of the as‐obtained phosphor are very close to the National Television Standard Committee standard values (x = 0.67, y = 0.33). All these characteristics suggest that this material is a promising red‐emitting phosphor candidate for white‐LEDs based on near‐UV LED chips. Copyright © 2012 John Wiley & Sons, Ltd.     

Intense green‐, red‐emitting Tb3+, Tb3+/Bi3+‐doped and Sm3+, Sm3+/La3+‐doped Ca2Al2SiO7 phosphors

This paper focuses on an optical study of a Tb³⁺/Bi³⁺‐doped and Sm³⁺/La³⁺‐ doped Ca₂Al₂SiO₇ phosphor synthesized using combustion methods. Here, Ca₂Al₂SiO₇:Sm³⁺ showed a red emission band under visible light excitation but, when it co‐doped with La³⁺ ions, the emission intensity was further enhanced. Ca₂Al₂SiO₇:Tb³⁺ shows the characteristic green emission band under near‐ultraviolet light excitation wavelengths, co‐doping with Bi³⁺ ions produced enhanced photoluminescence intensity with better colour tunable properties. The phosphor exhibited better phase purity and crystallinity, confirmed by X‐ray diffraction. Binding energies of Ca(2p), Al(2p), Si(2p), O(1s) were studied using X‐ray photoelectron spectroscopy. The reported phosphor may be a promising visible light excited red phosphor for light‐emitting diodes and energy conversion devices.     

Luminescence investigation of novel MgPbAl10O17:Tb3+ green‐emitting phosphor for solid‐state lighting

In this work, we studied the luminescence properties of Tb³⁺‐doped MgPbAl₁₀O₁₇ green phosphor. To understand the excitation mechanism and corresponding emission of the prepared phosphor, its structural, morphological and photoluminescence properties were investigated. In general, for green emission, Tb³ is used as an activator and the obtained excitation and emission spectra indicated that this phosphor can be effectively excited by a wavelength of 380 nm, and exhibits bright green emission centered at 545 nm corresponding to the f → f transition of trivalent terbium ions. The chromaticity coordinates were (C_x = 0.263, C_y = 0.723). The impact of Tb³⁺ concentration on the relative emission intensity was investigated, and the best doping concentration was found to be 2 mol%. This study suggests that Tb³⁺‐doped MgPbAl₁₀O₁₇ phosphor is a strong candidate for a green component in phosphor‐converted white light‐emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd.     

Luminescence properties of green‐emitting Ca2MgSi2O7:Eu2+ phosphor by a solid‐state reaction method

A europium (Eu)‐doped di‐calcium magnesium di‐silicate phosphor, Ca₂MgSi₂O₇:Eu²⁺, was prepared using a solid‐state reaction method. The phase structure, particle size, surface morphology, elemental analysis, different stretching mode and luminescence properties were analyzed by X‐ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM) with energy dispersive X‐ray spectroscopy (EDX), Fourier transform infrared (FTIR) spectroscopy, photoluminescence (PL) and mechanoluminescence (ML). The phase structure of Ca₂MgSi₂O₇:Eu²⁺ was an akermanite‐type structure, which belongs to the tetragonal crystallography with space group P4?2₁m; this structure is a member of the melilite group and forms a layered compound. The surface of the prepared phosphor was not found to be uniform and particle distribution was in the nanometer range. EDX and FTIR confirm the components of Eu²⁺‐doped Ca₂MgSi₂O₇ phosphor. Under UV excitation, the main emission peak appeared at 530 nm, belonging to the broad emission ascribed to the 4f⁶5d¹→4f⁷ transition of Eu²⁺. The ML intensity of the prepared phosphor increased linearly with increasing impact velocity. A CIE color chromaticity diagram and ML spectrum confirmed that the prepared Ca₂MgSi₂O₇:Eu²⁺ phosphor would emit green color and the ML spectrum was similar to that of PL, which indicated that ML is emitted from the same center of Eu²⁺ ions. Copyright © 2015 John Wiley & Sons, Ltd.     

A novel red‐emitting phosphor,KAl1‐xPO4Cl:Eux3+ (0.1 ≤ x ≤ 1.0)

A series of phosphors KAl_1‐xPO₄Cl:Eu_x³⁺ (0.1 ≤ x ≤ 1.0) was synthesized using a facile combustion method using urea as a fuel and their structural, morphological and photoluminescence properties were investigated. It was found that the particle size was in the range of 1–2 µm with an irregular shape. The f–f transitions of Eu³⁺ in the host lattice were assigned and discussed. The excitation and emission spectra indicated that this phosphor can be efficiently excited by ultraviolet (395 nm), and exhibit reddish orange emission corresponding to the ⁵D₀→⁷F_J (J = 0, 1, 2) transitions of Eu³⁺. The impact of the Eu³⁺ concentration on the relative emission intensity was investigated, and the best doping concentration is 0.5. The present study suggests that the KAl_0.5PO₄Cl: Eu_0.5³⁺ phosphor is a strong candidate as a red component for phosphor‐ converted white light‐emitting diodes (LEDs). Copyright © 2015 John Wiley & Sons, Ltd.     

Dy3+‐, Sm3+‐, Ce3+‐ and Tb3+‐activated optical properties of microcrystalline BaMgP2O7 phosphors

Photoluminescence (PL) and thermoluminescence (TL) properties of rare earth (RE) ion (RE = Dy³⁺, Sm³⁺, Ce³⁺, Tb³⁺) activated microcrystalline BaMgP₂O₇ phosphors are presented in this work. Non‐doped and doped samples of BaMgP₂O₇ were prepared using a solid state diffusion method and characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), PL and TL. The XRD measurement confirmed the phase purity of the BaMgP₂O₇ host matrix. The average particle size was found through SEM measurement to be around 2 μm. All activators using the PL technique displayed characteristic excitation and emission spectra that corresponded to their typical f → f and f → d transitions respectively. Thermoluminescence measurements showed that BaMgP₂O₇:RE (RE = Dy³⁺, Sm³⁺, Tb³⁺, Ce³⁺) and co‐doped BaMgP₂O₇:Ce³⁺,Tb³⁺ phosphors have also TL behaviour.     

Photoluminescence characteristics of novel Sm3+ ions-doped La1.4Al22.6O36 phosphor for n-UV w-LED

The combustion procedure was used to synthesize La_1.4Al_22.6O₃₆:Sm³⁺ phosphors. The X-ray diffraction (XRD) patterns and morphological and photoluminescence properties were investigated. The XRD patterns consisted of a hexagonal crystal structure. At 405 nm, the maximum excitation intensity was obtained. Following 405 nm excitation, three different emission peaks at 573, 604, and 651 nm were seen. Concentration quenching occurred at 1.5 mol% Sm³⁺ ions. The Commission Internationale de l'éclairage coordinates for the La_1.4Al_22.6O₃₆ phosphor with Sm³⁺ doping were 604 nm (x = 0.644, y = 0.355) falling in the red region. The findings implied that the prepared phosphor may be used to develop w-light-emitting diodes.