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.     

Luminescent properties and energy transfer in the green phosphors LaBSiO5:Tb3+,Ce3+

LaBSiO₅ phosphors doped with Ce³⁺ and Tb³⁺ were synthesized using the conventional solid‐state method at 1100 °C. The phase purity and luminescent properties of these phosphors are investigated. LaBSiO₅:Tb³⁺ phosphors show intense green emission, and LaBSiO₅ phosphors doped with Ce³⁺ show blue–violet emission under UV light excitation. LaBSiO₅ phosphors co‐doped with Ce³⁺ and Tb³⁺ exhibit blue–violet and green emission under excitation by UV light. The blue–violet emission is due to the 5d–4f transition of Ce³⁺ and the green emission is ascribed to the ⁵D₄ → ⁷ F₅ transition of Tb³⁺. The spectral overlap between the excitation band of Tb³⁺ and the emission band of Ce³⁺ supports the occurrence of energy transfer from Ce³⁺ to Tb³⁺, and the energy transfer process was investigated. Copyright © 2014 John Wiley & Sons, Ltd.     

Preparation and luminescence properties of KLaSiO4:Tb3+ phosphors

KLaSiO₄:Tb³⁺ phosphors were synthesized using the sol–gel method. The structure and luminescence properties of the materials were characterized using X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, thermogravimetry–differential thermal analysis, fluorescence spectra and calculated Commission Internationale de l'éclairage coordinates. The results showed that the material had a hexagonal structure, and that doping of Tb³⁺ did not change the crystal structure of KLaSiO₄. FTIR spectroscopy confirmed the existence of stretching vibrations of Si–O, bending vibrations of Si–O–Si, and asymmetric tensile vibrations of Si–O in KLaSiO₄. The excitation spectrum of the sample consisted of 4f⁷→5d¹ broadband absorption and the characteristic excitation peak of Tb³⁺, the excitation peak at 232 nm belongs to the spin allowed ⁷F_J→⁷D_J transition of Tb³⁺, the excitation peak at 268 nm belongs to the spin forbidden ⁷F_J→⁹D_J transition of Tb³⁺, and the absorption band of ⁷F_J→⁷D_J transition is split. Under excitation at 232 nm, the emission peak of the sample was composed of the ⁵D₄→⁷F_J (J = 6, 5, 4, 3) energy level transition of Tb³⁺. The highest emission peak is located at 543 nm, which belongs to the ⁵D₄→⁷F₅ transition and emits green light. Concentration quenching occurred when the Tb³⁺ doping concentration was greater than 1% mol, the quenching mechanism was an electric dipole–electric dipole action. When the ratio of citric acid to total metal ions was 1:1 and the annealing temperature was 800°C, the surface defects of the phosphors were greatly reduced, the quenching effect was reduced, and the luminous intensity reached the maximum.     

Structure and photoluminescent properties of green‐emitting terbium‐doped GdV1−xPxO4 phosphor prepared by solution combustion method

Terbium‐doped gadolinium orthovanadate (GdVO₄:Tb³⁺), orthophosphate monohydrate (GdPO₄·H₂O:Tb³⁺) and orthovanadate–phosphate (GdV,PO₄:Tb³⁺) powder phosphors were synthesized using a solution combustion method. X‐Ray diffraction analysis confirmed the formation of crystalline GdVO₄, GdPO₄·H₂O and GdV,PO₄. Scanning electron microscopy images showed that the powder was composed of an agglomeration of particles of different shapes, ranging from spherical to oval to wire‐like structures. The chemical elements present were confirmed by energy dispersive spectroscopy, and the stretching mode frequencies were determined by Fourier transform infrared spectroscopy. UV–visible spectroscopy spectra showed a strong absorption band with a maximum at 200 nm assigned to the absorption of VO₄^3? and minor excitation bands assigned to f → f transitions of Tb³⁺. Four characteristic emission peaks were observed at 491, 546, 588 and 623 nm, and are attributed to ⁵D₄ → ⁷F_j (j = 6, 5, 4 and 3). The photoluminescent prominent green emission peak (⁵D₄ → ⁷F₅) was centred at 546 nm. The structure and possible mechanism of light emission from GdV_1?xP_xO₄:% Tb³⁺ are discussed. Copyright © 2016 John Wiley & Sons, Ltd.     

Thermoluminescence and photoluminescence studies on γ‐ray‐irradiated Ce3+,Tb3+‐doped potassium chloride single crystals

Single crystals of KCl doped with Ce³⁺,Tb³⁺ were grown using the Bridgeman–Stockbarger technique. Thermoluminescence (TL), optical absorption, photoluminescence (PL), photo‐stimulated luminescence (PSL), and thermal‐stimulated luminescence (TSL) properties were studied after γ‐ray irradiation at room temperature. The glow curve of the γ‐ray‐irradiated crystal exhibits three peaks at 420, 470 and 525 K. F‐Light bleaching (560 nm) leads to a drastic change in the TL glow curve. The optical absorption measurements indicate that F‐ and V‐centres are formed in the crystal during γ‐ray irradiation. It was attempted to incorporate a broad band of cerium activator into the narrow band of terbium in the KCl host without a reduction in the emission intensity. Cerium co‐doped KCl:Tb crystals showed broad band emission due to the d–f transition of cerium and a reduction in the intensity of the emission peak due to ⁵D₃–⁷F_j (j = 3, 4) transition of terbium, when excited at 330 nm. These results support that energy transfer occurs from cerium to terbium in the KCl host. Co‐doping Ce³⁺ ions greatly intensified the excitation peak at 339 nm for the emission at 400 nm of Tb³⁺. The emission due to Tb³⁺ ions was confirmed by PSL and TSL spectra. Copyright © 2015 John Wiley & Sons, Ltd.     

Photoluminescence of Alq3‐ and Tb‐activated aluminium–tris(8‐hydroxyquinoline) complex for blue chip‐excited OLEDs

The tris(8‐hydroxyquinoline)–aluminium complex is the most important and widely studied as electron transporting and green light emitting material. Alq₃ and Tb_xAl_(1‐x)q₃ have been synthesized (where x = 0.1, 0.3, 0.5, 0.7 and 0.9) and blended films of Alq₃ and Tb_xAl_(1‐x)q₃ with PMMA and PS at different percentage weight (wt%) concentrations (e.g., 0.1, 1, 5, 10, 25 and 50 wt%) have been prepared. The synthesized materials and their blended thin films have been characterized by a photoluminescence (PL) technique; the synthesis and PL characterization are reported in this paper. The synthesized metal complex shows bright emission of green light with blue light excitation (440 nm) and the prepared Tb_xAl_(1‐x)q₃ phosphor may be applicable in blue chip‐excited OLEDs for the newly developed wallpaper lighting technology. Copyright © 2012 John Wiley & Sons, Ltd.     

Luminescence study of Eu3+doped Li6Y(BO3)3 phosphor for solid‐state lighting

In this study, Li₆Y_1–xEu_x(BO₃)₃ phosphor was successfully synthesized using a modified solid‐state diffusion method. The Eu³⁺ ion concentration was varied at 0.05, 0.1, 0.2, 0.5 and 1 mol%. The phosphor was characterized for phase purity, morphology, luminescent properties and molecular transmission at room temperature. The XRD pattern suggests a result closely matching the standard JCPDS file (#80‐0843). The emission and excitation spectra were followed to discover the luminescence traits. The excitation spectra indicate that the current phosphor can be efficiently excited at 395 nm and at 466 nm (blue light) to give emission at 595 and 614 nm due to the ⁵D₀ → ⁷F_j transition of Eu³⁺ ions. Concentration quenching was observed at 0.5 mol% Eu³⁺ in the Li₆Y_1–xEu_x(BO₃)₃ host lattice. Strong red emission with CIE chromaticity coordinates of phosphor is x = 0.63 and y = 0.36 achieved with dominant red emission at 614 nm the ⁵D₀ → ⁷ F₂ electric dipole transition of Eu³⁺ ions. The novel Li₆Y_1–xEu_x(BO₃)₃ phosphor may be a suitable red‐emitting component for solid‐state lighting using double‐excited wavelengths, i.e. near‐UV at 395 nm and blue light at 466 nm. 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.     

Tunable emission from LiBaBO3:Eu3+;Bi3+ phosphor for solid‐state lighting

Europium (Eu³⁺) and bismuth (Bi³⁺) co‐activated LiBaBO₃ powder phosphors were synthesized by a solid‐state reaction and the structure, particle morphology, optical and photoluminescent properties were investigated. X‐Ray diffraction patterns of the LiBaBO₃ phosphors crystallized in a pure monoclinic phase, i.e. there were no secondary phases due to either incidental impurities or undecomposed starting materials. Scanning electron microscopy images showed that the powders were made up of fluffy needle‐like particles that were randomly aligned. The band‐gap of the LiBaBO₃ host was estimated to be 3.33 eV from the UV/vis absorption data. Blue emission was observed from the LiBaBO₃ host, which is ascribed to self‐activation of the host matrix. In addition, greenish‐blue (493 nm) and red (613 nm) emissions were observed from europium‐doped samples and were attributed to the emissions of Eu²⁺ and Eu³⁺, respectively. Furthermore, after codoping with Bi³⁺, the emission intensity of Eu³⁺ located at 613 nm was significantly enhanced. From the Commission Internationale de I′Eclairage (CIE) color coordinates, white emission was observed from LiBa_1–xBO₃:xEu³⁺ (x = 0.020 and 0.025) phosphor powders with color coordinates of x = 0.368, y = 0.378 and x = 0.376, y = 0.366, respectively.     

Intense green light emission and thermoluminescence glow curve analysis of Tb3+-activated CaY2O4 phosphor

Here, the synthesis and luminescence analysis of the Tb³⁺-activated phosphor were reported. The CaY₂O₄ phosphors were synthesized using a modified solid-state reaction method with a variable doping concentration of Tb³⁺ ion (0.1–2.5 mol%). As synthesized, the phosphor was characterized using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analysis techniques for the optimized concentration of doping ions. The prepared phosphor showed a cubic structure, and FTIR analysis confirmed functional group analysis. It was discovered that the intensity of 1.5 mol% was higher than at other concentrations after the photoluminescence (PL) excitation and emission spectra were recorded for different concentrations of doping ions. The excitation was monitored at 542 nm, and the emission was monitored at 237 nm. At 237 nm excitation, the emission peaks were found at 620 nm (⁵D₄→⁷F₃), 582 nm (⁵D₄→⁷F₄), 542 nm (⁵D₄→⁷F₅), and 484 nm (⁵D₄→⁷F₆). The 1931 CIE (x, y) chromaticity coordinates showed the distribution of the spectral region calculated from the PL emission spectra. The values of (x = 0.34 and y = 0.60) were very close to dark green emission. Therefore, the produced phosphor would be very useful for light-emitting diode (green component) applications. Thermoluminescence glow curve analysis for various concentrations of doping ions and various ultraviolet (UV) exposure times was carried out, and a single broad peak was found at 252°C. The computerized glow curve deconvolution method was used to obtain the related kinetic parameters. The prepared phosphor exhibited an excellent response to UV dose and could be useful for UV ray dosimetry.     

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.     

Improvement of light emission of Mn-doped Zn(2) SiO(4) phosphors with sodium

Mn‐doped willemite (Zn₂SiO₄:Mn) green phosphor were synthesized by sol–gel technology. The effect of the addition of sodium, as in the composition Zn_{(1.92 – X)} Na_XMn_0.08SiO₄, on the emission behavior was studied. FT–IR and EPR results revealed that sodium ion is incorporated into the lattice and results in the formation of isolated Mn²⁺ and Mn–Mn pairs. The maximum emission intensity of the sample under ultraviolet (UV) excitation occurred at the sodium concentration of x = ~0.03. The green emission at about 525 nm is assigned to Mn²⁺–Mn²⁺ pair centres on nearest neighbour Zn sites. The highest intensity of the green emission for x = ~0.03 is well close to the highest concentration of the Mn²⁺–Mn²⁺ pair. Copyright © 2012 John Wiley & Sons, Ltd.     

Tunable luminescence properties and energy transfer in LaAl11O18:Eu,Tb phosphor

Eu²⁺ and Tb³⁺ singly doped and co‐doped LaAl₁₁O₁₈ phosphors were prepared by a combustion method using urea as a fuel. The phase structure and photoluminescence (PL) properties of the prepared phosphors were characterized by powder X‐ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence excitation and emission spectra. When the content of Eu²⁺ was fixed at 0.01, the emission chromaticity coordinates could be adjusted from blue to green region by tuning the contents of Tb³⁺ ions from 0.01 to 0.03 through an energy transfer (ET) process. The fluorescence data collected from the samples with different contents of Tb³⁺ into LaAl₁₁O₁₈: Eu, show the enhanced green emission at 545 nm associated with ⁵D₄ –⁷F₅ transitions of Tb³⁺. The enhancement was attributed to ET from Eu²⁺ to Tb³⁺, and therefore Eu²⁺ ion acts as a sensitizer (an energy donor) while Tb³⁺ ion as an activator. The ET from Eu²⁺ to Tb³⁺ is performed through dipole–dipole interaction. The ET efficiency and critical distance were also calculated. The present Eu²⁺–Tb³⁺ co‐doped LaAl₁₁O₁₈ phosphor will have potential application for UV convertible white light‐emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd.     

Intensity enhancement of photoluminescence in Tb3+/Eu3+ co-doped Ca14Zn6Al10O35 phosphor for WLEDs

This article focuses on the effect of monovalent cation doping on the optical properties of rare earth (RE = Eu³⁺, Tb³⁺) co-doped Ca₁₄Zn₆Al₁₀O₃₅ which has been synthesized by a low temperature combustion method. Crystalline phase of the Ca₁₄Zn₆Al₁₀O₃₅ phosphor was examined and confirmed by X-ray diffraction measurement. Under near-ultraviolet light excitation Eu³⁺-doped Ca₁₄Zn₆Al₁₀O₃₅ phosphor exhibit characterization of Eu³⁺ emission bands that are located at a maximum wavelength (λ_max) of approximately 470 nm and other peaks centred at 593 nm and 615 nm, respectively. With Tb³⁺-doped Ca₁₄Zn₆Al₁₀O₃₅ phosphor showing a green emission band centred at 544 nm under near-ultraviolet range. Furthermore, we studied the energy transfer process in Eu³⁺/Tb³⁺pair and enhancement in photoluminescence (PL) intensity with doping different charge compensation. Here we obtained the optimum PL emission intensity of the phosphor in broad and intense visible spectral range which may be significant for the fabrication of white light emitting diodes (WLEDs).     

Tunable emission,energy transfer and charge compensation in SrMoO4:Sm3+,Tb3+,Na+ phosphor

A series of SrMoO₄:Sm³⁺,Tb³⁺,Na⁺ phosphors was synthesized using a high‐temperature solid‐state reaction method in air. On excitation at 290 nm, SrMoO₄:Sm³⁺,Tb³⁺ phosphor emitted light that varied systematically from green to reddish‐orange on changing the Sm³⁺ and Tb³⁺ ion concentrations. The emission intensities of SrMoO₄:Sm³⁺ and SrMoO₄:Sm³⁺,Tb³⁺ phosphors were increased two to four times due to charge compensation when Na⁺ was added as a charge compensator. The luminescence mechanism and energy transfer could be explained using energy‐level diagrams of the MoO₄^2– group, Sm³⁺ and Tb³⁺ ions. SrMoO₄:Sm³⁺,Tb³⁺,Na⁺ could be used as reddish‐orange phosphor in white light‐emitting diodes (LEDs) based on an ~ 405 nm near‐UV LED chip. This research is helpful in adjusting and improving the luminescence properties of other phosphors. Copyright © 2015 John Wiley & Sons, Ltd.     

Multi-color luminescence of Sm3+-doped Na2YMg2V3O12 phosphor potentially applicable in white-LEDs

A novel multi-color emitting Na₂YMg₂V₃O₁₂:Sm³⁺ phosphor was synthesized using a solid-state reaction, and its crystal structure, luminescence properties, and thermal stability were studied. Charge transfer within the (VO₄)³⁻ groups in the Na₂YMg₂V₃O₁₂ host led to a broad emission band between 400 and 700 nm, with a maximum at 530 nm. The Na₂Y_1−xMg₂V₃O₁₂:xSm³⁺ phosphors exhibited a multi-color emission band under 365 nm near-ultraviolet (near-UV) light, consisting of the green emission of the (VO₄)³⁻ groups and sharp emission peaks at 570 nm (yellow), 618 nm (orange), 657 nm (red), and 714 nm (deep red) of Sm³⁺ ions. The optimal doping concentration of Sm³⁺ ions was found to be 0.05 mol%, and the dipole–dipole (d–d) interaction was primarily responsible for the concentration quenching phenomenon. Using the acquired Na₂YMg₂V₃O₁₂:Sm³⁺ phosphors, commercial BaMgAl₁₀O₁₇:Eu²⁺ blue phosphor, and a near-UV light-emitting diode (LED) chip, a white-LED lamp was designed and packaged. It produced bright neutral white light, manifesting a CIE coordinate of (0.314, 0.373), a color rendering index (CRI) of 84.9, and a correlated color temperature (CCT) of 6377 K. These findings indicate the potential of Na₂YMg₂V₃O₁₂:Sm³⁺ phosphor to be used as a multi-color component for solid-state illumination.     

Novel red colour emitting Ca0.995Mg2(SO4)3:0.5Eu2+ phosphor under ultraviolet,blue, and green excitation for plant growth LEDs

In the recent few years, Eu²⁺- and Mn⁴⁺-activated phosphors are widely used as potential colour converters for indoor plant cultivation lighting application due to their marvellous luminescence characteristics as well as low cost. In this investigation, we synthesized novel red colour-emitting Ca_(2−x)Mg₂(SO₄)₃:xmol% Eu²⁺ (x = 0–1.0 mol%) phosphors via a solid-state reaction method in a reducing atmosphere. The photoluminescence (PL) excitation spectra of synthesized phosphors exhibited a broad excitation band with three excitation bands peaking at 349 nm, 494 nm, and 554 nm. Under these excitations, emission spectra exhibited a broad band in the red colour region at ~634 nm. The PL emission intensity was measured for different concentrations of Eu²⁺. The maximum Eu²⁺ doping concentration in the Ca₂Mg₂(SO₄)₃ host was observed for 0.5 mol%. According to Dexter theory, it was determined that dipole–dipole interaction was responsible for the concentration quenching. The luminous red colour emission of the sample was confirmed using Commission international de l'eclairage colour coordinates. The results of PL excitation and emission spectra of the prepared phosphors were well matched with excitation and emission wavelengths of phytochrome P_R. Therefore, from the entire investigation and obtained results it was concluded that the synthesized Ca_0.995Mg₂(SO₄)₃:0.5mol%Eu²⁺ phosphor has huge potential for plant cultivation application.     

Structural and luminescence properties of Y2‐xGeMoO8:REx (RE = Eu,Tb) phosphors

Y_2‐xGeMoO₈:RE_x (RE = Eu, Tb) phosphors were synthesized using a facile sol–gel method. The morphology and structure of the phosphors were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X‐ray diffraction (XRD); while their luminescent properties were investigated by photoluminescence (PL) spectrometry. Our results reveal that all of these Y_2‐xGeMoO₈:RE_x (RE = Eu, Tb) phosphors adopted the tetragonal phase, belonging to Scheelite (CaWO₄) structure. The obtained YGeMoO₈:Eu phosphors exhibit a strong emission in the red light range which can be assigned to the ⁵D₀ → ⁷F₂ transition of Eu³⁺ when it is excited at 459 nm. Under 392 and 489 nm excitation, the YGeMoO₈:Tb phosphors present predominant green emission (⁵D₄ → ⁷F₅) at 540 nm. The highest emission of the phosphors can be achieved by adjusting the doping concentration to be 0.25 for Eu³⁺ and 0.15 for Tb³⁺, respectively. The promising luminescence properties of these materials indicate that they can be potentially applied to white‐light‐emitting diodes. Copyright © 2013 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.     

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.