Effect of Dy3+ or Eu2+ co‐activator on a BaCa(SO4)2:Ce3+ mixed alkaline earth sulfate phosphor

The individual emission and energy transfer between Ce³⁺ and Eu²⁺ or Dy³⁺ in BaCa(SO₄)₂ mixed alkaline earth sulfate phosphor prepared using a co‐precipitation method is described. The phosphor was characterized by X‐ray diffraction (XRD) and photoluminescence (PL) studies and doped by Ce;Eu and Dy rare earths. All phosphors showed excellent blue–orange emission on excitation with UV light. PL measurements reveal that the emission intensity of Eu²⁺ or Dy³⁺ dopants is greater than when they are co‐doped with Ce³⁺. An efficient Ce³⁺ → Eu²⁺ [²T_2g(4f⁶5d) → ⁸S_7/2(4f₇)] and Ce³⁺ → Dy³⁺ (⁴ F_9/2 → ⁶H_15/2 and ⁴ F_9/2 → ⁶H_13/2) energy transfer takes place in the BaCa(SO₄)₂ host. A strong blue emission peak was observed at 462 nm for Eu²⁺ ions and an orange emission peak at 574 nm for Dy³⁺ ions. Hence, this phosphor may be used as a lamp phosphor. Copyright © 2015 John Wiley & Sons, Ltd.     

Optical properties of CaAl(SO4)2Br:RE (RE = Dy,Eu, Ce) novel phosphors

A new phosphor CaAl(SO₄)₂Br doped with Dy, Ce and Eu is reported. Rare earth (Dy, Eu and Ce)‐doped polycrystalline CaAl(SO₄)₂Br phosphors were prepared using a wet chemical reaction method and studied for X‐ray diffraction and photoluminescence (PL) characteristics. Dy³⁺ emission in the CaAl(SO₄)₂Br lattice was observed at 484 and 574 nm in the blue and yellow regions of the spectrum, which are assigned to ⁴ F_9/2 → ⁶H_15/2 and ⁴ F_9/2 → ⁶H_13/2 transitions of the Dy³⁺ ion, respectively. While the PL emission spectra of CaAl(SO₄)₂Br:Ce phosphor showed Ce³⁺ emission at 347 nm due to 5d → 4f transition of the Ce³⁺ ion. In a CaAl(SO₄)₂Br:Eu lattice, Eu³⁺ emissions were observed at 593 and 617 nm, coming from the ⁵D₀ → ⁷ F₁ and ⁵D₀ → ⁷ F₂ electron transitions, respectively. The PL study showed that the intensity of electric dipole transition at 617 nm dominates over that of magnetic dipole transition at 590 nm. The maximum PL intensity was obtained for a 1 mol% concentration of Eu³⁺ in CaAl(SO₄)₂Br host lattice. The results showed that the material may be a promising candidate as a blue‐, yellow‐ and red‐emitting phosphor. Copyright © 2013 John Wiley & Sons, Ltd.     

Luminescence and spectroscopic studies of halosulfate phosphors: a review

This review discusses the photoluminescence (PL) characteristics of halosulfate phosphors developed by us. Halosulfate phosphors KCaSO₄Cl:X,Y (X = Eu or Ce; Y = Dy or Mn) and Na₆(SO₄)₂FCl (doped with Dy, Ce or Eu) were prepared using a solid‐state diffusion method. The mechanism of energy transfer from Eu²⁺→Dy³⁺, Ce³⁺→Dy³⁺ and Ce³⁺→Mn²⁺ has also been studied. Dy³⁺ emission in the host at 475 and 570 nm is observed due to ⁴F_9/2→⁶H_15/2 and ⁴F_9/2→⁶H_13/2 transition, whereas the PL emission spectra of Na₆(SO₄)₂FCl:Ce phosphor shows Ce³⁺ emission at 322 nm due to 5d→4f transition of the Ce³⁺ ion. The main property of KCaSO₄Cl is its very high sensitivity, particularly when doped by Dy, Mn or Pb activators. This review also discusses the PL characteristics of some new phosphors such as LiMgSO₄F, Na₆Pb₄(SO₄)₆Cl₂, Na₂₁Mg(SO₄)₁₀Cl₃ and Na₁₅(SO₄)₅F₄Cl. Copyright © 2014 John Wiley & Sons, Ltd.     

Dy(3+) and Mn(2+) emission in fluoride- and chloride-based Na(3) (SO(4) )X (X = F or Cl) phosphors

In the present study, Na₃(SO₄)X (X = F or Cl) halosulphate phosphors have been synthesized by the solid‐state diffusion method. The phase formation of the compounds Na₃(SO₄)F and Na₃(SO₄)Cl were confirmed by X‐ray powder diffraction (XRD) measurement. Photoluminescence (PL) excitation spectrum measurement of Na₃(SO₄)F:Ce³⁺ and Na₃(SO₄)Cl:Ce³⁺ shows this phosphor can be efficiently excited by near‐ultraviolet (UV) light and presents a dominant luminescence band centred at 341 nm for Ce³⁺, which is responsible for energy transfer to Dy³⁺and Mn²⁺ ions. The efficient Ce³⁺ → Dy³⁺ energy transfer in Na₃(SO₄)F and Na₃(SO₄)Cl under UV wavelength was observed due to ⁴ F_9/2 to ⁶H_15/2 and ⁶H_13/2 level, while Ce³⁺ → Mn²⁺ was observed due to ⁴ T₁ state to ⁶A₁. The purpose of the present study is to develop and understanding the photoluminescence properties of Ce³⁺‐, Dy³⁺‐ and Mn²⁺‐doped fluoride and chloride Na₃(SO₄)X (X = F or Cl) luminescent material, which can be the efficient phosphors in many applications, such as scintillation applications, TL dosimetry and the lamp industry, etc. Copyright © 2012 John Wiley & Sons, Ltd.     

Photoluminescence properties of LiBaPO4:M3+ phosphor for near‐UV light‐emitting diode (M = Eu and Dy)

A novel phosphor LiBaPO₄ doped with rare earths Eu and Dy prepared by high temperature solid‐state reaction method is reported. The phosphors were characterized by X‐ray powder diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL). The emission and excitation spectra of these materials were measured at room temperature with a spectrofluorophotometer. The excitation spectra of LiBaPO₄:Eu³⁺ phosphor can be efficiently excited by 394 nm, which is matched well with the emission wavelength of near‐UV light‐emitting diode (LED) chip. PL properties of Eu³⁺‐doped LiBaPO₄ exhibited the characteristic red emission coming from ⁵D₀ → ⁷ F₁ (593 nm) and ⁵D₀ → ⁷ F₂ (617 nm) electronic transitions with color co‐ordinations of (0.680, 0.315). The results demonstrated that LiBaPO₄:Eu³⁺ is a potential red‐emitting phosphor for near‐UV LEDs. Emission spectra of LiBaPO₄:Dy³⁺ phosphors showed efficient blue (481 nm) and yellow (574 nm) bands, which originated from ⁴ F_9/2 → ⁶H_15/2 and ⁴ F_9/2 → ⁶H_13/2 transitions of the Dy³⁺ ion, respectively. The 574 nm line is more intense than the 481 nm lines, which indicates that the site Dy³⁺ is located with low symmetry. This article summarizes fundamentals and possible applications of optically useful inorganic phosphates with visible photoluminescence of Eu³⁺ and Dy³⁺ ions. Copyright © 2015 John Wiley & Sons, Ltd.     

Study of luminescence and effect of Dy3+ on NaMgSO4Cl:Ce chlorosulphate phosphor

Chlorosulphate NaMgSO₄Cl phosphor doped with Ce³⁺ and co‐doped by Dy³⁺ prepared by the wet chemical method was studied for its photoluminescence and thermoluminescence (TL) characteristics. The emission spectrum of Ce³⁺ shows dominant peaks at 346 nm (excitation 270 nm) due to 5d → 4f transition. Efficient energy transfer occurs from Ce³⁺ → Dy³⁺ ions. Dy³⁺ emission at 485 nm and 576 nm is due to ⁴ F_9/2 → ⁶H_15/2 and ⁴ F_9/2 → ⁶H_13/2 transitions of Dy³⁺ ion respectively. The TL glow curves of NaMgSO₄Cl:Ce and Ce,Dy have been recorded for various concentrations at a heating rate of 2 °C/s irradiated by γ‐rays at a dose rate of 0.995 kGy/h for 1 Gy, which peaks at about 241 °C and 247‐312 °C respectively. Further, in changing the concentration level, the general structure of the intensity is found to increase. The main property of this phosphor is its sensitivity even for low concentrations of rare earth ions and low γ‐ray dose. There is still scope for higher doses of γ‐radiation. The phosphor presented may be used as a lamp phosphor as well as for TL studies. Copyright © 2014 John Wiley & Sons, Ltd.     

Enhanced luminescence and white light emission from Eu3+‐co‐doped K3Ca2(SO4)3Cl:Dy3+ phosphor with near visible ultraviolet excitation for white LEDs

The luminescent properties of europium (Eu)‐ and dysprosium (Dy)‐co‐doped K₃Ca₂(SO₄)₃Cl halosulfate phosphors were analyzed. This paper reports the photoluminescence (PL) properties of K₃Ca₂(SO₄)₃Cl microphosphor doped with Eu and Dy and synthesized using a cost‐effective wet chemical method. The phosphors were characterized by X‐ray diffraction and scanning electron microscopy. The CIE coordinates were calculated to display the color of the phosphor. PL emission of the prepared samples show peaks at 484 nm (blue), 575 nm (yellow), 594 nm (orange) and 617 nm (red). The emission color of the Eu,Dy‐co‐doped K₃Ca₂(SO₄)₃Cl halophosphor depends on the doping concentration and excitation wavelength. The addition of Eu in K₃Ca₂(SO₄)₃Cl:Dy greatly enhances the intensity of the blue and yellow peaks, which corresponds to the ⁴ F_9/2 → ⁶H_15/2 and ⁴ F_9/2 → ⁶H_13/2 transitions of Dy³⁺ ions (under 351 nm excitation). The Eu³⁺/Dy³⁺ co‐doping also produces white light emission for 1 mol% of Eu³⁺, 1 mol% of Dy³⁺ in the K₃Ca₂(SO₄)₃Cl lattice under 396 nm excitation, for which the calculated chromaticity coordinates are (0.35, 0.31). Thus, K₃Ca₂(SO₄)₃Cl co‐doped with Eu/Dy is a suitable candidate for NUV based white light‐emitting phosphors technology. Copyright © 2014 John Wiley & Sons, Ltd.     

Luminescence of Eu and Ce in K3Ca2(SO4)3F fluoride material

A new halophosphor K₃Ca₂(SO₄)₃ F activated by Eu or Ce and K₃Ca₂(SO₄)₃ F:Ce,Eu co‐doped halosulfate phosphor has been synthesized by the co‐precipitation method and characterized for its photoluminescence (PL). The PL emission spectra of the K₃Ca₂(SO₄)₃ F :Ce phosphor show emission at 334 nm when excited at 278 nm due to 5d → 4f transition of Ce³⁺ ions. In the K₃Ca₂(SO₄)₃ F:Eu lattice, Eu²⁺ (440 nm) as well as Eu³⁺ (596 nm and 615 nm) emissions have been observed showing ⁵D₀ → ⁷ F₁ and ⁵D₀ → ⁷ F₂ transition of the Eu³⁺ ion, which is in the blue and red region of the visible spectrum respectively. The trivalent europium ion is very useful for studying the nature of metal coordination in various systems owing to its non‐degenerate emitting ⁵D₀ state. K₃Ca₂(SO₄)₃ F:Ce,Eu is suitable for Ce³⁺ → Eu²⁺ → Eu³⁺ energy transfer in which Ce³⁺and Eu²⁺ play the role of sensitizers and Eu²⁺ and Eu³⁺ act as the activators. The observations presented in this paper are relevant for lamp phosphors. Copyright © 2015 John Wiley & Sons, Ltd.     

Structural,morphological, and photoluminescence properties of RE (RE = Dy3+, Eu3+, Sm3+)-doped CaAlBO4 phosphor synthesized by combustion method

The CaAlBO₄:RE (RE = Dy³⁺, Eu³⁺, Sm³⁺) phosphor were prepared via combustion synthesis and studied by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) analysis, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), photoluminescence (PL) spectra and CIE coordinates. The phase formation of the obtained phosphor was analyzed by XRD and the result was confirmed by standard PDF Card No. 1539083. XRD data successfully indicated pure phase of CaAlBO₄ phosphor. The crystal structure of CaAlBO₄ phosphor is orthorhombic with space group Ccc2 (37). The SEM image of CaAlBO₄ phosphor reveals an agglomerated morphology and non-uniform particle size. The EDS image provides evidence of the elements present and the chemical makeup of the materials. Under the 350 nm excitation, the emission spectrum of Dy³⁺ activated CaAlBO₄ phosphor consists of two main groups of characteristic peaks located at 484 and 577 nm which are ascribed to ⁴F_9/2 → ⁶H_15/2 and ⁴F_9/2 → ⁶H_13/2 transition of Dy³⁺ respectively. The PL emission spectra of CaAlBO₄:Eu³⁺ phosphor shows characteristics bands observed around 591 and 613 nm, which corresponds to ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂ transition of Eu³⁺ respectively, upon 395 nm excitation wavelength. The emission spectra of Sm³⁺ activated CaAlBO₄ phosphor shows three characteristic bands observed at 565, 601 and 648 nm which emits yellow, orange and red color. The prominent emission peak at the wavelength 601 nm, which is attributed to ⁴G_5/2 → ⁶H_7/2 transition, displays an orange emission. The CIE color coordinates of CaAlBO₄:RE (RE = Dy³⁺, Eu³⁺, Sm³⁺) phosphor are calculated to be (0.631, 0.368), (0.674, 0.325) and (0.073, 0.185). As per the obtained results, CaAlBO₄:RE (RE = Dy³⁺, Eu³⁺, Sm³⁺) phosphor may be applicable in eco-friendly lightning technology.     

Resonant and non‐resonant energy transfer from Ce3+ → X (X = Tb3+, Eu3+ or Dy3+) in NaMgSO4F material

An inorganic NaMgSO₄F fluoride material was prepared by the wet chemical method and studied for its photoluminescence (PL) and resonant–non‐resonant energy transfer (RET and NORET) capabilities between Ce³⁺ → Tb³⁺, Ce³⁺ → Eu³⁺ and Ce³⁺ → Dy³⁺ rare earth ions. The Tb³⁺ emission for Ce³⁺ → Tb³⁺ transfers under ultraviolet (UV) wavelengths peaked at 491, 547, and 586 nm, for excitation at 308 nm due to ⁵D₄ → ⁷F_J (J = 4, 5, 6) transitions. Eu emission spectra were observed at 440 nm (Eu²⁺), 593 nm and 616 nm (Eu³⁺) recorded for different concentrations of materials, whereas Dy³⁺ emission from Ce³⁺ → Dy³⁺ transfer under UV wavelengths peaked at 485 nm and 577 nm due to ⁴F_9/2 → ⁶H_15/2 and ⁶H_13/2 transitions. The purpose of the present study is to understand the RET and NORET effects of Tb³⁺, Eu³⁺ and Dy³⁺ co‐doping in a NaMgSO₄F:Ce³⁺ luminescent material, which could be used as a green‐emitting material for lamp phosphors.     

Energy transfer between Ce3+ → Gd3+ or Tb3+ in KNaSO4 microphosphor

KNaSO₄ microphosphor doped with Ce,Gd and Ce,Tb and prepared by a wet chemical method was studied using X‐ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL) characterization. KNaSO₄ has a 5‐µm particle size detected by SEM. KNaSO₄:Ce³⁺,Tb³⁺ showed blue and green emission (at 494 nm, 557 nm, 590 nm) of Tb³⁺ due to ⁵D₄ → ⁷F_J (J = 4, 5, 6) transitions. KNaSO₄:Ce³⁺,Gd³⁺ showed luminescence in the ultraviolet (UV) light region at 314 nm for an excitation at 271 nm wavelength. It was observed that efficient energy transfer took place from Ce³⁺ → Gd³⁺ and Ce³⁺ → Tb³⁺ sublattices indicating that Ce³⁺ could effectively sensitize Gd³⁺ or Tb³⁺ (green emission). Ce³⁺ emission weakened and Gd³⁺ or Tb³⁺ enhanced the emission significantly in KNaSO₄. This paper discusses the development and understanding of photoluminescence and the effect of Tb³⁺ and Gd³⁺ on KNaSO₄:Ce³⁺. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and luminescence properties of Ca3Ga2Si3O12:RE3+ (RE = Eu/Tb) powder phosphors

Rare earth ions (Eu³⁺ or Tb³⁺)‐activated Ca₃ Ga₂ Si₃O₁₂ (CaGaSi) phosphors were synthesized by using a sol–gel method. Photoluminescence spectra of Eu³⁺:CaGaSi phosphors exhibited five emission bands at 578, 592, 612, 652 and 701 nm, which were assigned to the transitions (⁵D₀ → ⁷F₀, ⁷F_1, ⁷F₂, ⁷F₃ and ⁷F₄), respectively, with an excitation wavelength of λ_exci = 392 nm. Among these, the transition ⁵D₀ → ⁷F₂ (612 nm) displayed bright red emission. In the case of Tb³⁺:CaGaSi phosphors, four emission bands were observed at 488 (⁵D₄ → ⁷F₆), 543 (⁵D₄ → ⁷F₅), 584 (⁵D₄ → ⁷F₄) and 614 nm (⁵D₄ → ⁷F₃) from the measurement of PL spectra with λ_exci = 376 nm. Among these, the transition ⁵D₄ → ⁷F₅ at 543 nm displayed bright green emission. The structure and morphology of the phosphors were studied from the measurements of X‐ray diffraction (XRD), scanning electron microscopy (SEM) and energy‐dispersive X‐ray analysis (EDAX) results. Copyright © 2011 John Wiley & Sons, Ltd.     

Photoluminescence properties of LiTi2 − xEux(PO4)3 phosphor

A solid‐state reaction route‐based LiTi_{2 ? x}Eu_x(PO₄)₃ was phosphor synthesized for the first time to evaluate its luminescence performance by excitation, emission and lifetime (τ) measurements. The LiTi_{2 ? x}Eu_x(PO₄)₃ phosphor was excited at λ_exci. = 397 nm to give an intense orange–red (597 nm) emission attributed to the ⁵D₀ → ⁷F₁ magnetic dipole (ΔJ = ±1) transition and red (616 nm) emission (⁵D₀ → ⁷F₂), which is an electric dipole (ΔJ = ±2) transition of the Eu³⁺ ion. Beside this, excitation and emission spectra of host LiTi₂(PO₄)₃ powder were also reported. The effect of Eu³⁺ concentration on luminescence characteristics was explained from emission and lifetime profiles. Concentration quenching in the LiTi_{2 ? x}Eu_x(PO₄)₃ phosphor was studied from the Dexter's model. Dipole–quadrupole interaction is found to be responsible for energy transfer among Eu³⁺ ions in the host lattice. The LiTi_{2 ? x}Eu_x(PO₄)₃ phosphor displayed a reddish‐orange colour realized from a CIE chromaticity diagram. We therefore suggest that this new phosphor could be used as an optical material of technological importance in the field of display devices. Copyright © 2016 John Wiley & Sons, Ltd.     

Photoluminescence of Dy3+ activator sensitized by Ce3+ in KNaSO4 microphosphor

The KNaSO₄ microphosphor doped with Ce or Ce and Dy prepared by a wet chemical method was studied by scanning electron microscopy (SEM) and characterized by photoluminescence (PL). KNaSO₄ has a 5‐µm particle size detected by SEM. The KNaSO₄:Ce³⁺ spectrum shows a single emission band at 327 nm for an excitation of 269 nm due to 5d → 4f transition of the Ce³⁺ ion, indicating weak spin orbiting coupling of the Ce³⁺ ground state. Efficient energy transfer takes place from Ce³⁺ → Dy³⁺ sublattices indicating that Ce³⁺ could effectively sensitize Dy³⁺ (orange emission) and that the Ce³⁺ emission weakens significantly in KNaSO₄. The powder form of prepared KNaSO₄ show negligible change in morphologies and hence no effect on the particle size. The characteristics of this powder could provide improved luminescence properties. The development and understanding of this photoluminescence and the effect of Dy³⁺ on KNaSO₄: Ce³⁺ are discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

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.     

Photoluminescence properties of aeschynite‐type LaNbTiO6:RE3+ (RE = Tb,Dy, Ho) down‐converting phosphors

In this study, a series of LaNbTiO₆:RE³⁺ (RE = Tb, Dy, Ho) down‐converting phosphors were synthesized using a modified sol–gel combustion method, and their photoluminescence (PL) properties were investigated as a function of activator concentration and annealing temperature. The resultant particles were characterized using X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, UV/Vis diffuse reflectance spectroscopy and PL spectra. The highly crystalline LaNbTiO₆:RE³⁺ (RE = Tb, Dy, Ho) phosphors with an average size of 200–300 nm obtained at 1100°C have an orthorhombic aeschynite‐type structure and exhibit the highest luminescent intensity in our study range. The emission spectra of LaNbTiO₆:RE³⁺ (RE = Tb, Dy, Ho) phosphors under excitations at UV/blue sources are mainly composed of characteristic peaks arising from the f–f transitions of RE³⁺, including 489 nm (⁵D₄ → ⁷F₆) and 545 nm (⁵D₄ → ⁷F₅) for Tb³⁺, 476 and 482 nm (⁴F_9/2 → ⁶H_15/2) and 571 nm (⁴F_9/2 → ⁶H_13/2) for Dy³⁺, and 545 nm (⁵F₄ + ⁵S₂ → ⁵I₈) for Ho³⁺, respectively. The luminescent mechanisms were further investigated. It can be expected that these phosphors are of intense interest and potential importance for many optical applications. Copyright © 2013 John Wiley & Sons, Ltd.     

Emission analysis of RE3+ (RE = Sm,Dy):B2O3‐TeO2‐Li2O‐AlF3 glasses

This article reports on the optical properties of 0.5% mol of Sm³⁺, Dy³⁺ ion‐doped B₂O₃‐TeO₂‐Li₂O‐AlF₃ (LiAlFBT) glasses. The glass samples were characterized by optical absorption and emission spectra. Judd‐Ofelt theory was applied to analyze the optical absorption spectra and calculate the intensity parameters and radiative properties of the emission transitions. The emission spectra of Sm³⁺ and Dy³⁺:LiAlFBT glasses showed a bright reddish‐orange emission at 598 nm (⁴G_5/2 → ⁶H_7/2) and an intense yellow emission at 574 nm (⁴F_9/2 → ⁶H_13/2), respectively. Full width at half maximum (FWHM), stimulated emission cross section, gain bandwidth and optical gain values were also calculated to extend the applications of the Sm³⁺ and Dy³⁺:LiAlFBT glasses. Copyright © 2012 John Wiley & Sons, Ltd.     

Luminescent properties of MAl(SO4)2Br:Eu3+ (M = Sr or Mg) red phosphors for near‐UV light‐emitting diodes

Eu³⁺‐activated MAl(SO₄)₂Br phosphors (where M = Mg or Sr) are successfully prepared using a wet chemical reaction technique. The samples are characterized by X‐ray diffraction (XRD) and photoluminescence (PL) spectroscopies. The XRD pattern revealed that both the samples are microcrystalline in nature. PL of Eu³⁺‐doped SrAl(SO₄)₂Br and MgAl(SO₄)₂Br phosphors exhibited characteristic red emission coming from the ⁵D₀ → ⁷F₂ (616 nm) electron transition, when excited by 396 nm wavelength of light. The maximum intensity of luminescence was observed at a concentration of 1 mol% Eu³⁺. The intensity of the electric dipole transition at 616 nm is greater than that of the magnetic dipole transition at 594 nm. The results showed that MAl(SO₄)₂Br:Eu³⁺, (M = Mg, Sr) phosphors have potential application in near‐UV light‐emitting diodes as efficient red‐emitting phosphor. Copyright © 2014 John Wiley & Sons, Ltd.     

Optical properties and energy transfer of Eu2+/Ce3+ co‐activated Na3Ca6(PO4)5 phosphor

Ce³⁺/Eu²⁺ co‐doped Na₃Ca₆(PO₄)₅ phosphors were prepared using a combustion‐assisted synthesis method. X‐Ray powder diffraction (XRD) analysis confirmed the formation of a Na₃Ca₆(PO₄)₅ crystal phase. Na₃Ca₆(PO₄)₅:Eu²⁺ phosphors have an efficient bluish‐green emission band that peaks at 489 nm, whereas Ce³⁺‐doped Na₃Ca₆(PO₄)₅ showed a bright emission band at 391 nm. Analysis of the experimental results suggests that enhancement of the Eu²⁺ emission intensity in co‐doped Na₃Ca₆(PO₄)₅:Eu²⁺,Ce³⁺ phosphors is due to a resonance‐type energy transfer from Ce³⁺ to Eu²⁺ ions, which is predominantly governed by an exchange interaction mechanism. These results indicate that Ce³⁺/Eu²⁺ co‐doped Na₃Ca₆(PO₄)₅ is potentially useful as a highly efficient, bluish‐green emitting, UV‐convertible phosphor for white‐light‐emitting diodes. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and photoluminescence characteristics of (Y,Gd)BO3:RE (RE = Eu3+, Ce3+, Dy3+ and Tb3+) phosphors for blue chip and near‐UV white LEDs

A series of Eu³⁺‐, Ce³⁺‐, Dy³⁺‐ and Tb³⁺‐doped (Y,Gd)BO₃ phosphors was synthesized by a solid‐state diffusion method. X‐Ray diffraction confirmed their hexagonal structure and the scanning electron microscopy results showed crystalline particles. The excitation spectra revealed that (Y,Gd)BO₃ phosphors doped with Eu³⁺, Ce³⁺ , Dy³⁺ and Tb³⁺ are effectively excited with near UV‐light of 395 nm/blue light, 364, 351 and 314 nm, respectively. Photoluminescence spectra of Eu³⁺‐, Ce³⁺‐ and Tb³⁺/Dy³⁺‐doped phosphor showed intense emission of reddish orange, blue and white light, respectively. The phosphor Y_0.60Gd_0.38BO₃:Ce_0.02 showed CIE 1931 color coordinates of (0.158, 0.031) and better color purity compared with commercially available blue BAM:Eu²⁺ phosphor. The phosphor (Y,Gd)BO₃ doped with Eu³⁺, Dy³⁺ and Tb³⁺ showed CIE 1931 color coordinates of (0.667, 0.332), (0.251, 0.299) and (0.333, 0.391) respectively. Significant photoluminescence characteristics of the prepared phosphors indicate that they might serve as potential candidates for blue chip and near‐UV white light‐emitting diode applications. Copyright © 2015 John Wiley & Sons, Ltd.