Eu3+‐tetrakis β‐diketonate complexes for solid‐state lighting application

Eu³⁺–β‐diketonate complexes are used, for example, in solid‐state lighting (SSL) or light‐converting molecular devices. However, their low emission quantum efficiency due to water molecules coordinated to Eu³⁺ and low photostability are still problems to be addressed. To overcome such challenges, we synthesized Eu³⁺ tetrakis complexes based on [Q][Eu(tfaa)₄] and [Q][Eu(dbm)₄] (Q1 = C₂₆H₅₆N⁺, Q2 = C₁₉H₄₂N⁺, and Q3 = C₁₇H₃₈N⁺), replacing the water molecules in the tris stoichiometry. The tetrakis β‐diketonates showed desirable thermal stability for SSL and, under excitation at 390 nm, they displayed the characteristic Eu³⁺ emission in the red spectral region. The quantum efficiencies of the dbm complexes achieved values as high as 51%, while the tfaa complexes exhibited lower quantum efficiencies (28–33%), but which were superior to those reported for the tris complexes. The structures were evaluated using the Sparkle/PM7 model and comparing the theoretical and the experimental Judd–Ofelt parameters. [Q1][Eu(dbm)₄] was used to coat a near‐UV light‐emitting diode (LED), producing a red‐emitting LED prototype that featured the characteristic emission spectrum of [Q1][Eu(dbm)₄]. The emission intensity of this prototype decreased only 7% after 30 h, confirming its high photostability, which is a notable result considering Eu³⁺ complexes, making it a potential candidate for SSL.     

Synthesis and photoluminescence of EuII in barium zinc orthosilicate: a novel green color emitting phosphor for white‐LEDs

A series of Eu²⁺‐activated barium orthosilicates (BaZnSiO₄) were synthesized using a high‐temperature solid‐state reaction. A photoluminescence excitation study of Eu²⁺ shows a broad absorption band in the range of 270–450 nm, with multiple absorption peak maxima (310, 350 and 400 nm) due to 4f–5d electronic transition. The emission spectra of all the compositions show green color emission (in the spectral region 450–550 nm with a peak maximum at 502 nm and a shoulder at ~ 490 nm) with appropriate Comission Internationale de l'Eclairage (CIE) color coordinates. The two emission peaks are due to the presence of Eu²⁺ in two different Ba sites in the BaZnSiO₄ host lattice. The energy transfers between the Eu²⁺ ions in BaZnSiO₄ host are elucidated from the critical concentration quenching data based on the electronic multipolar interaction. All Eu²⁺‐activated BaZnSiO₄ phosphor materials can be efficiently excited in the ultraviolet (UV) to near UV‐region (270–420 nm), making them attractive candidate as a green phosphor for solid state lighting–white light‐emitting diodes.     

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.     

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.     

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.     

Synthesis,density functional theory calculations and luminescence of lanthanide complexes with 2,6‐bis[(3‐methoxybenzylidene)hydrazinocarbonyl] pyridine Schiff base ligand

A pyridine‐diacylhydrazone Schiff base ligand, L = 2,6‐bis[(3‐methoxy benzylidene)hydrazinocarbonyl]pyridine was prepared and characterized by single crystal X‐ray diffraction. Lanthanide complexes, Ln–L, {[LnL(NO₃)₂]NO₃.xH₂O (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Er)} were prepared and characterized by elemental analysis, molar conductance, thermal analysis (TGA/DTGA), mass spectrometry (MS), Fourier transform infra‐red (FT‐IR) and nuclear magnetic resonance (NMR) spectroscopy. Ln–L complexes are isostructural with four binding sites provided by two nitro groups along with four coordination sites for L. Density functional theory (DFT) calculations on L and its cationic [LnL(NO₃)₂]⁺ complexes were carried out at the B3LYP/6–31G(d) level of theory. The FT‐IR vibrational wavenumbers were computed and compared with the experimentally values. The luminescence investigations of L and Ln–L indicated that Tb–L and Eu–L complexes showed the characteristic luminescence of Tb(III) and Eu(III) ions. Ln–L complexes show higher antioxidant activity than the parent L ligand.     

Tunable luminescence and energy transfer in Ca3SiO4Cl2:Ce3+,Li+,Mn2+,Eu2+ phosphors

A series of color‐tunable Ca_{3–2x‐y‐z}SiO₄Cl₂ (CSC):xCe³⁺,xLi⁺,yMn²⁺,zEu²⁺ phosphors with low temperature phase structure was synthesized via the sol–gel method. An energy transfer process from Ce³⁺ to Mn²⁺ in CSC:0.01Ce³⁺,0.01Li⁺,yMn²⁺ (y = 0.03–0.09) and the mechanism was verified to be an electric dipole–dipole interaction. The Ce³⁺ and Mn²⁺ emission intensities were greatly enhanced by co‐doping Eu²⁺ ions into CSC:0.01Ce³⁺,0.01Li⁺,0.07Mn²⁺ phosphors due to competitive energy transfers from Eu²⁺/Ce³⁺ to Mn²⁺, and Ce³⁺ to Eu²⁺. Under 332 nm excitation, CSC:0.01Ce³⁺,0.01Li+,0.07Mn²⁺,zEu²⁺ (z = 0.0005–0.002) exhibited tunable emission colors from green to white with coexisting orange, green and violet‐blue emissions. These phosphors could have potential application in white light‐emitting diodes.     

The luminescent properties and crystal structure of Sr(1.5‐x)‐(1.5y)Mg0.5SiO4:xEu2+,yCe3+ blue phosphor synthesized by co‐precipitation method

In order to improve the luminescent performance of silicate blue phosphors, Sr_{(1.5‐x)‐(1.5y)}Mg_0.5SiO₄:xEu²⁺,yCe³⁺ phosphors were synthesized using one‐step calcination of a precursor prepared by chemical co‐precipitation. The crystal structure and luminescent properties of the phosphors were analyzed using X‐ray diffraction and fluorescence spectrophotometry, respectively. Because the activated ions (Eu²⁺) can occupy two different types of sites (Sr₁ and Sr₂), the emission spectrum of Eu²⁺ excited at 350 nm contains two single bands (EM₁ and EM₂) in the wavelength range 400–550 nm, centered at 463 nm, and the emission intensity first increases and then decreases with increasing concentrations of Eu²⁺ ions. Co‐doping of Ce³⁺ ions can greatly enhance the emission intensity of Eu²⁺ by transferring its excitation energy to Eu²⁺. Because of concentration quenching, a higher substitution concentration of Ce³⁺ can lead to a decrease in the intensity. Meanwhile, the quantum efficiency of the phosphor is improved after doping with Ce³⁺, and a blue shift phenomenon is observed in the CIE chromaticity diagram. The results indicate that Sr_{(1.5‐x)‐(1.5y)}Mg_0.5SiO₄:xEu²⁺,yCe³⁺ can be used as a potential new blue phosphor for white light‐emitting diodes.     

Enhancing the luminescence of Eu3+/Eu2+ ion‐doped hydroxyapatite by fluoridation and thermal annealing

This paper reports a novel way for the synthesis of a europium (Eu)‐doped fluor‐hydroxyapatite (FHA) nanostructure to control the luminescence of hydroxyapatite nanophosphor, particularly, by applying optimum fluorine concentrations, annealed temperatures and pH value. The Eu‐doped FHA was made using the co‐precipitation method followed by thermal annealing in air and reducing in a H₂ atmosphere to control the visible light emission center of the nanophosphors. The intensities of the OH^? group decreased with the increasing fluorine concentrations. For the specimens annealed in air, the light emission center of the nanophosphor was 615 nm, which was emission from the Eu³⁺ ion. However, when they were annealed in reduced gas (Ar + 5% H₂), a 448 nm light emission center from the Eu²⁺ ion of FHA was observed. The presence of fluorine in Eu‐doped FHA resulted in a significant enhancement of nanophosphor luminescence, which has potential application in light emission and nanomedicine.     

Synthesis and luminescence characterization of Y2BaZnO5:RE (RE = Eu3+, Tb3+, Pr3+ and Sm3+) phosphors

Modified synthesis and luminescence of Y₂BaZnO₅ phosphors activated with the rare earths (RE) Eu³⁺, Tb³⁺, Pr³⁺ and Sm³⁺ are reported. RE₂BaZnO₅ phosphors have attracted attention because of their interesting magnetic and optical properties; and are usually prepared using a two‐step solid‐state reaction. In the first step, carbonates or similar precursors are thoroughly mixed and heated at 900°C to decompose them to oxides. To eliminate the unwanted phases like BaRE₂O₄, the resulting powders are reheated at 1100°C for a long time. We prepared Y₂BaZnO₅ phosphors activated with various activators by replacing the first step with combustion synthesis. The photoluminescence results are presented. The photoluminescence results for Eu³⁺, Tb³⁺ and Pr³⁺ are in good agreement with the literature. However, photoluminescence emission from Sm³⁺ has not been documented previously. The excitation spectrum of Eu³⁺ is dominated by a charge transfer band around 261 nm, and an additional band around 238 nm is always present, irrespective of the type of activator. The presence of this band for all these different types of activators was interpreted as host absorption.     

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).     

Luminescence properties of a novel red phosphor 6LaPO4–3La3PO7–2La7P3O18:Eu3+

Eu³⁺‐doped 6LaPO₄–3La₃PO₇–2La₇P₃O₁₈ red luminescent phosphors were synthesized by co‐deposition and high‐temperature solid‐state methods and its polyphase state was confirmed by X‐ray diffraction analysis. Transmission electron microscopy showed the grain morphology as a mixture of rods and spheres. Luminescence properties of the phosphor were investigated and its red emission parameters were evaluated as a function of Eu³⁺ concentration (3.00–6.00 mol%). Excitation spectra of 6LaPO₄–3La₃PO₇–2La₇P₃O₁₈:Eu³⁺ showed strong absorption bands at 280, 395, and 466 nm, while the luminescence spectra exhibited prominent red emission peak centred at 615 nm (⁵D₀→⁷F₂) in the red region. CIE chromaticity coordinates of the 6LaPO₄–3La₃PO₇–2La₇P₃O₁₈:5%Eu³⁺ phosphor were (0.668, 0.313) in the red region, and defined its potential application as a red phosphor.     

Photoluminescence and thermoluminescence properties of Eu2+ doped and Eu2+,Dy3+ co‐doped Ba2MgSi2O7 phosphors

In this work, we report the preparation, characterization, comparison and luminescence mechanisms of Eu²⁺‐doped and Eu²⁺,Dy³⁺‐co‐doped Ba₂MgSi₂O₇ (BMSO) phosphors. Prepared phosphors were synthesized via a high temperature solid‐state reaction method. All prepared phosphors appeared white. The phase structure, particle size, and elemental analysis were analyzed using X‐ray diffraction (XRD), transmission electron microscopy (TEM) and energy‐dispersive X‐ray (EDX) analysis. The luminescence properties of the phosphors were investigated by thermoluminescence (TL) and photoluminescence (PL). The PL excitation and emission spectra of Ba₂MgSi₂O₇:Eu²⁺ showed the peak to be around 381 nm and 490 nm respectively. The PL excitation spectrum of Ba₂MgSi₂O₇:Eu²⁺Dy³⁺ showed the peak to be around 341 nm and 388 nm, and the emission spectrum had a broad band around 488 nm. These emissions originated from the 4f⁶ 5d¹ to 4f⁷ transition of Eu²⁺. TL analysis revealed that the maximum TL intensity was found at 5 mol% of Eu²⁺ doping in Ba₂MgSi₂O₇ phosphors after 15 min of ultraviolet (UV) light exposure. TL intensity was increased when Dy³⁺ ions were co‐doped in Ba₂MgSi₂O₇:Eu²⁺ and maximum TL intensity was observed for 2 mol% of Dy³⁺. TL emission spectra of Ba_1.95MgSi₂O₇:0.05Eu²⁺ and Ba_1.93MgSi₂O₇:0.05Eu²⁺,0.02Dy³⁺ phosphors were found at 500 nm. TL intensity increased with UV exposure time up to 15 min, then decreased for the higher UV radiation dose for both Eu doping and Eu,Dy co‐doping. The trap depths were calculated to be 0.54 eV for Ba_1.95MgSi₂O₇:0.05Eu²⁺ and 0.54 eV and 0.75 eV for Ba_1.93MgSi₂O₇:0.05Eu²⁺,0.02Dy³⁺ phosphors. It was observed that co‐doping with small amounts of Dy³⁺ enhanced the thermoluminescence properties of Ba₂MgSi₂O₇ phosphor. Copyright © 2016 John Wiley & Sons, Ltd. [Correction added on 5 April 2016, after first online publication: The following parts of the abstract have been edited for consistency. '4f65d1' has been corrected to '4f⁶ 5d¹', '4f7' has been corrected to '4f⁷', 'Ba1.95' has been corrected to 'Ba_1.95' and 'Ba1.93' has been corrected to 'Ba_1.93' respectively.]     

Synthesis and optical properties of Eu3+‐substituted glaserite‐type orthovanadates CsK2Y[VO4]2

A new Eu³⁺‐substituted CsK₂Y[VO₄]₂ glaserite‐type orthovanadate phosphor was synthesized by the conventional high temperature solid‐state reaction method. The phase purity was confirmed by powder X‐ray diffraction study and it reveals that all the compositions crystallize in the hexagonal structure. The morphology and elemental composition were measured by FE‐SEM with Energy Dispersive Analysis Of X Rays (EDAX). The band gap is determined by diffuse reflectance spectra. The self‐activated luminescence of the host and Eu³⁺‐substituted luminescence behaviours were studied in detail by photoluminescence spectra. The host CsK₂Y[VO₄]₂ shows green emission, whereas the Eu³⁺‐substituted compositions show red emission. Effect of Eu³⁺ concentrations on the photoluminescence behaviour were also been studied. The Eu³⁺‐doped samples show not only several sharp emission lines but also a broad emission band due to presence of the [VO₄]^3? in the host, which clearly indicates that there is incomplete energy transfer from (VO₄) charge transfer band to Eu³⁺_. The life time of the phosphors also been studied. The Commission Internationale de l'Eclairage (CIE) chromaticity colour coordinates were calculated and it is very much closer to the National Television Standard Committee (NTSC) standards. These investigations evidently reveal that the self‐activated and Eu³⁺‐activated phosphors show a great potential applications as a red phosphor for solid‐state lighting includes white light‐emitting diodes (wLEDs).     

Sol‐gel synthesis and luminescent properties of red‐emitting Y(P,V)O4:Eu3+ phosphors

Eu³⁺‐activated Y(P,V)O₄ phosphors were prepared by the EDTA sol‐gel method, and the corresponding morphologies and luminescent properties were investigated. The sample particles were relatively spheroid with size of 2–3 µm and had a smooth surface. The excitation spectra for Y(P,V)O₄:Eu³⁺ consisted of three strong excitation bands in the 200–350 nm range, which were attributed to a Eu³⁺‐ O^2? charge‐transfer band and ¹A₁?¹ T₁/¹ T₂ transitions in VO₄^3?. The as‐synthesized phosphors exhibited a highly efficient red luminescence at 613 nm due to the Eu^{3+ 5}D₀?⁷ F₂ electric dipole transition. With the increase in the V⁵⁺/P⁵⁺ ratio, the luminescence intensity of the red phosphor under UV excitation was greatly improved due to enhanced VO₄^3? → Eu³⁺ energy transfer. Copyright © 2015 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.     

Sr2ZnWO6:Eu3+,Bi3+,Li+: a potential white‐emitting phosphor for near‐ultraviolet white light‐emitting diodes

A series of Sr₂ZnWO₆ phosphors co‐doped with Eu³⁺, Bi³⁺ and Li⁺ were prepared using the Pechini method. The samples were tested using X‐ray diffraction and luminescence spectroscopy. The results show that the samples can be effectively excited by near‐ultraviolet (UV) and UV light. The introduction of Bi³⁺ and Li⁺ significantly enhances the fluorescence emission of Sr₂ZnWO₆:Eu³⁺ and changes the light emitted by the phosphors from bluish‐green to white. When excited at 371 nm, Sr_2–x–zZn_1–yWO₆:xEu³⁺,yBi³⁺,zLi⁺ (x = 0.05, y = 0.05, z = 0.05, 0.1 and 0.15) samples emit high‐performance white light. Intense red–orange emission is also observed when excited by UV light. The obtained phosphor is a potential white‐emitting phosphor that could meet the needs of excitation sources with near‐UV chips. In addition, this phosphor might have promising application as a red–orange emitting phosphor for white light‐emitting diodes based on UV light‐emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis,photophysics, electrochemistry,thermal stability and electroluminescent performances of a new europium complex with bis(β‐diketone) ligand containing carbazole group

We synthesized a new europium complex [Eu(ecbpd)₃(Phen)] with bis(β‐diketone) ligand containing a carbazole group, in which ecbpd and Phen are dehydro‐3,3′‐(9‐ethyl‐9H‐carbazole‐3,6‐diyl)bis(1‐phenylpropane‐1,3‐dione) and 1,10‐phenanthroline, respectively. Its UV/vis and photoluminescent spectra, quantum yield, luminescence lifetime, electrochemistry, thermal stability and electroluminescent performances were studied. This europium complex showed low efficiency luminescence, which is probably due to the mismatching energy levels of its ligand and Eu³⁺, as well as the double Eu³⁺ core resonance.     

Ultrasound assisted synthesis of CaF2:Eu3+ phosphor nanoparticles

In this work, the optical and structural properties of ultrasonically prepared CaF₂:Eu³⁺ nanoparticles have been reported. Ultrasonically prepared CaF₂:Eu³⁺ phosphor shows orange, red emission bands at 591 nm and 612 nm, respectively, when it is excited by 394 light‐emitting diode (LED) excitation wavelengths. Further phosphor materials are well characterized by X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM) techniques to confirm the phase purity, metal oxygen (MO) bonding and crystallites size of the materials. Here synthesized materials show a tube‐like structure under 100 nm resolution and 0.1 mol% is the best doping value of the europium ion (Eu³⁺) in calcium fluoride (CaF₂) that shows highest intensity when prepared with an ultrasound assisted method.     

Luminescent properties of sol–gel processed red‐emitting phosphor Ca0.6Sr0.4–1.5x‐0.5yMo0.4 W0.6O4:EuxLiy

A series of red‐emitting phosphors Ca_0.6Sr_{0.4–1.5x‐0.5y}Mo_0.4 W_0.6O₄:Eu_xLi_y (x = 0.02–0.12, y = 0–0.12) has been synthesized by a sol‐gel method. The effects of calcining temperature, concentrations of Li⁺ and Eu³⁺, and compensation ions on the luminescent properties were investigated. X‐ray diffraction and scanning electron microscopic results showed that as‐prepared phosphors were of single phase with several microns. The Li⁺ compensated compositions showed remarkably intense red emission at 619 nm. The emission intensity of the series reached maximum for compositions at x = 0.08 and y = 0.08 when the calcining temperature was 900 °C. Copyright © 2014 John Wiley & Sons, Ltd.