Enhanced red emission from BaMoO4: Eu3+ by Bi3+ co‐doping

A series of Bi³⁺,Eu³⁺‐doped BaMoO₄ phosphors was synthesized using a hydrothermal method. The crystal structure, morphology and optical properties of the phosphors were studied using X‐ray diffraction (XRD), scanning electron microscope (SEM) and photoluminescence (PL) measurements. Three different particle morphologies were detected in the SEM observation. The energy dispersive spectroscopy (EDS) results indicated that the solubility of Bi³⁺ in spherical or rugby‐like BaMoO₄ particles was very low and the excess Bi³⁺ element was cumulated in the irregular particles. Characteristic emissions of Eu³⁺ ions (⁵D₀ → ⁷F_J; J = 0, 1, 2, 3, 4) were observed under excitation in ultraviolet (UV) light, with the most intense transition being the ⁵D₀ → ⁷F₂ transition. Energy transfer from MoO₄^2? and Bi³⁺ to Eu³⁺ can be readily achieved. Red emission intensity of Eu³⁺ was enhanced by a factor of two by co‐doping with a small amount of Bi³⁺. Optical properties as a function of Bi³⁺ content were studied and the optimum Bi³⁺ content in BaMoO₄ nanocrystals was determined to be 0.4 mol%.     

Optical properties of Eu2+/Eu3+ mixed valence phosphor Ca2SiO2F2:Eu2+/Eu3+

The Eu²⁺/Eu³⁺ mixed valence phosphor Ca₂SiO₂F₂:Eu²⁺/Eu³⁺ was prepared using a solid‐state reaction synthesis method in a CO atmosphere, and the optical properties were investigated. The spectroscopic properties revealed that Ca²⁺ ions were occupied by both Eu²⁺ and Eu³⁺ ions in Ca₂SiO₂F₂, and both ions were able to generate their characteristic emissions. A broad 5d → 4f Eu²⁺ band at ~470 nm and narrow 4f → 4f Eu³⁺ peaks upon excitation with n‐UV light were observed. The ratio between Eu²⁺ and Eu³⁺ emissions changed regularly, and the relative intensity of the red component from Eu³⁺ became systematically stronger with increasing overall Eu content. As a result, the emission color of these phosphors can be tunable from blue to pink under n‐UV light excitation.     

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.     

Eu3+‐doped polystyrene and polyvinylidene fluoride nanofibers made by electrospinning for photoluminescent fabric designing

Eu³⁺‐doped polystyrene and polyvinylidene fluoride (PVDF/Eu³⁺ and PS/Eu³⁺) nanofibers were made using electrospinning. These fibers were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT‐IR), energy dispersive spectroscopy (EDX) and photoluminescence (PL). Spectral analysis of PVDF/Eu³⁺ and PS/Eu³⁺ nanofibers was based on their emission spectra. A bright red emission was noticed from Eu³⁺ that was assigned to the hypersensitive ⁵D₀ → ⁷F₂ transition. The enhanced intensity ratios of ⁵D₀ → ⁷F₂ to ⁵D₀ → ⁷F₁ transitions in the nanofibers indicated a more polarized chemical environment for the Eu³⁺ ions and greater hypersensitivity for the ⁵D₀ → ⁷F₂ transition, which showed the potential for application in various polymer optoelectronic devices. The Eu³⁺‐doped polymer (PVDF/Eu³⁺ and PS/Eu³⁺) nanofibers are suitable for the photoluminescent white light fabric design of smart textiles. This paper focuses on the potential application of smart fabrics to address challenges in human life.     

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 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.     

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.     

Luminescence properties of neodymium,samarium, and europium niobate and tantalate thin films

Thin films of lanthanide orthoniobate LnNbO₄ (LnNO) and orthotantalate LnTaO₄ (LnTO), (Ln = Nd, Sm, Eu) were fabricated using the sol–gel method with subsequent spin-coating on the PbZrO₃/Al₂O₃ substrate and annealing at 1000°C. X-ray diffraction patterns showed monoclinic M-LnNbO₄ or M´-LnTaO₄, which coexists with the orthorhombic or tetragonal phase. X-ray photoelectron spectroscopy demonstrated the presence of Nd³⁺, Sm³⁺/Sm²⁺ and Eu³⁺/Eu²⁺ ions. The luminescence properties of polymorphic films were investigated. Excitation spectra of PbZrO₃ interlayer represented broad bands at 410 and 550 nm that were assigned to charge transfer bands (CTB). In all films, the CTB broad band at ~275 nm related to charge transfer transition of Ln³⁺→O²⁻ and NbO₄³⁻ or TaO₄³⁻ groups. In excitation spectra, ⁴I_9/2→⁴G_5/2 (Nd³⁺), ⁶H_5/2→⁶P_3/2 (Sm³⁺) and ⁷F₀→⁵L₆ (Eu³⁺) transitions (at 585, 402 and 395 nm), respectively were found to be more intense than any other Ln³⁺ transition. The emission spectra showed narrow and intense bands at 1065, 600, and 614 nm that were ascribed to Nd³⁺, Sm³⁺, and Eu³⁺ 4f–f intraconfigurational transitions ⁴F_3/2→⁴I_11/2, ⁴G_5/2→⁶H_7/2, and ⁵D₀→⁷F₂, respectively. The excellent luminescence properties of films make them new potential groups for visible and/or near-infrared applications such as sensors and imaging equipment.     

Photoluminescence properties of Ca2Al2O5:RE3+ (RE = Eu,Dy and Tb) phosphors for solid state lighting

Ca₂Al₂O₅:Eu³⁺, Ca₂Al₂O₅:Dy³⁺ and Ca₂Al₂O₅:Tb³⁺ phosphors were synthesized using a combustion synthesis method. The prepared phosphors were characterized by X‐ray powder diffraction for phase purity, by scanning electron microscopy for morphology, and by photoluminescence for emission and excitation measurements. The Ca₂Al₂O₅:Eu³⁺ phosphors could be efficiently excited at 396 nm and showed red emission at 594 nm and 616 nm due to ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂ transitions. Dy³⁺‐doped phosphors showed blue emission at 482 nm and yellow emission at 573 nm. Ca₂Al₂O₅:Tb³⁺ phosphors showed emission at 545 nm when excited at 352 nm. Concentration quenching occurred in both Eu³⁺ and Dy³⁺phosphors at 0.5 mol%. Photoluminescence results suggested that the aluminate‐based phosphor could be a potential candidate for application in environmentally friendly based lighting technologies.     

Photoluminescence enhancement in Na3SO4Cl:X (X = Ce3+, Eu3+ or Dy3+) material

The compound Na₃SO₄Cl X (X = Ce³⁺, Eu³⁺ or Dy³⁺) prepared by the wet chemical method was studied for its photoluminescence (PL) and energy transfer characteristics. The PL from Na₃SO₄Cl:Ce³⁺ shows strong emission at 322 nm at an excitation of 272 nm. Therefore, an efficient Ce³⁺ → Dy³⁺, Eu²⁺ → Dy³⁺ and Eu²⁺ → Eu³⁺ energy transfer had taken place in this host. The Dy³⁺ emission caused by Ce³⁺ → Dy³⁺ energy transfer under ultraviolet (UV) wavelengths peaked at around 477 nm and 572 nm due to ⁴ F_9/2 → ⁶H_15/2 and ⁶H_13/2 transitions with yellow–orange emission in the Na₃SO₄Cl lattice. An intense Dy³⁺ emission was observed at 482 and 576 nm caused by the Eu²⁺ → Dy³⁺ energy transfer process and due to ⁴ F_9/2 → ⁶H_15/2 and ⁴ F_9/2 → ⁶H_13/2 transitions respectively. The Eu³⁺ blue to red light emission caused by the Eu²⁺ → Eu³⁺ energy transfer peaked at 593 nm and 617 nm due to ⁵D₀ → ⁵D₃ transitions. The presence of trivalent Eu in Na₃SO₄Cl suggested the presence of Eu³⁺ in the host compound that occupied two different lattice sites and that peaked at 593 and 617 nm due to ⁵D₀ → ⁷ F₁ and ⁵D₀ → ⁷ F₂ transitions respectively. The trivalent europium ion is very useful for studying the nature of metal coordination in various systems due to its non‐degenerate emitting ⁵D₀ state. The present paper discusses the photoluminescence characteristics of Eu²⁺ → Dy³⁺ and Eu²⁺ → Eu³⁺ energy transfer. This compound may be useful as a lamp phosphor. Copyright © 2015 John Wiley & Sons, Ltd.     

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).     

Photoluminescence and structural analysis of trivalent europium doped MLaAl3O7 (M = Ba,Ca, Mg and Sr) nanophosphors

The solution combustion technique was used to synthesize MLaAl₃O₇ (M = Ba, Ca, Mg, and Sr) nanophosphors‐doped with Eu³⁺ using metal nitrates as precursors. The photoluminescence (PL) emission spectra exhibited three peaks at 587–591, 610–616, and 653–654 corresponding to ⁵D₀→⁷F₁, ⁵D₀→⁷F₂, and ⁵D₀→⁷F₃ transitions, respectively. Upon excitation at 254 nm, these nanophosphors displayed strong red emission with the dominant peak attributed to the ⁵D₀→⁷F₂ transition of Eu³⁺. The materials were further heated at 900 and 1050°C for 2 h to examine the consequence of temperature on crystal lattice and PL emission intensity. X‐ray diffraction (XRD) analysis proved that all the synthesized materials were of a crystalline nature. CaLaAl₃O₇ material has a tetragonal crystal structure with space group P421m. Scherer's equation was used to calculate the crystallite size of synthesized phosphors using XRD data. A Fourier transformation infrared study was used to observe the stretching vibrations of metal–oxygen bonds. Infrared peaks for stretching vibrations corresponding to lanthanum–oxygen and aluminium–oxygen bonds were found at 582 and 777 cm^–1 respectively for CaLaAl₃O₇ phosphor material. Transmission electron microscopy images were used to determine the size of particles (18–37 nm for the as‐prepared materials) and also to analyze the three‐dimensional view of these materials. The experimental data indicate that these materials may be promising red‐emitting nanophosphors for use in white light‐emitting diodes.     

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.     

Ho3+‐doped strontium–aluminium–bismuth–borate glasses for green light emission

Strontium–aluminium–bismuth–borate glasses (SAlBiB) doped with different concentrations of Ho³⁺ were prepared using conventional melt quenching technique and their structural and optical properties investigated. X‐ray diffraction and scanning electron microscopy analysis were used to study the structural properties. Optical properties were studied by measuring the optical absorption and visible luminescence spectra. The Judd–Ofelt (J‐O) theory was applied to evaluate J‐O intensity parameters, Ω_λ (λ = 2, 4 and 6). Using J‐O intensity parameters, radiative properties such as spontaneous transition probabilities (A_R), branching ratios (β_R) and radiative lifetimes (τ_R) were determined. From the emission spectra, a strong green emission nearly at 549 nm corresponding to the transition, ⁵S₂(⁵F₄)→⁵I₈ was observed. Emission peak positions (λ_P), effective bandwidths (Δλ_eff) and stimulated emission cross‐sections (σ_p) were calculated for the observed emission transitions, ⁵F₃→⁵I₈, ⁵S₂(⁵F₄)→⁵I₈ and ⁵F₅→⁵I₈ of Ho³⁺ in all the glass matrices. Chromaticity color coordinates were calculated using the emission spectra. The experimental results suggest that SAlBiB glass matrix with 1.5 mol% of Ho³⁺ has better emission properties. Copyright © 2014 John Wiley & Sons, Ltd.     

Spectroscopic and photoluminescence characterization of Dy3+ in Sr0.5Ca0.5TiO3 phosphor

The spectroscopic and photoluminescence characteristics of trivalent dysprosium (Dy³⁺)‐doped Sr_0.5Ca_0.5TiO₃ phosphor materials synthesized via solid‐state reaction method were studied. The X‐ray diffraction profile confirmed the orthorhombic perovskite structure of the prepared samples. Judd–Ofelt analysis was carried out to obtain the intensity parameters and predicted radiative properties of Sr_0.5Ca_0.5TiO₃:2wt%Dy³⁺. The photoluminescence spectrum of Dy³⁺‐doped Sr_0.5Ca_0.5TiO₃ showed three emission peaks at 481, 574 and 638 nm corresponding to ⁴F_9/2→⁶H_15/2, ⁴F_9/2→⁶H_13/2 and ⁴F_9/2→⁶H_11/2 transitions respectively. The variation of luminescence intensity with different excitation wavelengths and Dy³⁺ concentrations is discussed. The decay profiles of ⁴F_9/2 excited levels of Dy³⁺ ions show bi‐exponential behaviour and also a decrease in average lifetime with increase in Dy³⁺ concentration. Yellow to blue luminescence intensity ratio, CIE chromaticity co‐ordinates and correlated color temperature were also calculated for different concentrations of Dy³⁺‐doped Sr_0.5Ca_0.5TiO₃ phosphor at different λ_ex. Copyright © 2015 John Wiley & Sons, Ltd.     

Noncytotoxic Dy3+-activated glass emits cool white light for near ultraviolet-based white light-emitting diodes,visible lasers,and biomedical applications

Using the melt quenching technique, a lithium zinc borate glass (LZB) system with trivalent dysprosium ions (Dy³⁺) was synthesized, and the luminescence and lasing properties of these materials were examined for the generation of white light. Structural investigation through X-ray diffraction revealed that the prepared glass had an amorphous nature. The optimized glass containing 0.5 Dy³⁺ had a direct optical band gap of 2.782 eV and an indirect optical band gap of 3.110 eV. A strong excitation band at 386 nm (⁶H_15/2→⁴I_13/2) was recognized in the ultraviolet (UV) light region of its excitation spectrum. Emission bands could be seen in the photoluminescence spectrum at 659, 573, and 480 nm under the 386 nm excitation. These transitions of emission resembled electronic transitions such as (⁴F_9/2→⁶H_11/2), (⁴F_9/2→⁶H_13/2), and (⁴F_9/2→⁶H_15/2). In a pristine glass matrix, the higher intensity ratio of yellow to blue can result in the production of white light. The optimized Dy³⁺ ion concentration was observed to be 0.5 mol%. In addition, an analysis of lifetime decay was conducted for all synthesized glasses, and their decay trends were systematically investigated. Noticeably, we assessed the photometric parameters and found that they were close to the white light standard. Furthermore, a cytotoxicity study was carried out using lung fibroblast (WI-38) cell lines for the optimized 0.5Dy³⁺-doped LZB glass and it appeared to be noncytotoxic. It is clear from the results that the noncytotoxic LZB glass doped with 0.5 Dy³⁺ ions could be a suggestive choice for the manufacture of white light-emitting diodes and lasers using near-UVs.     

ZnWO4:Eu3+ phosphor with intense blue LED excitation: photoluminescence and electron density distribution analysis

A high intensity 464 nm excitable ZnWO₄:Eu³⁺ red‐emitting phosphor for warm white lighting applications was prepared using a solid‐state reaction method by varying the dopant Eu³⁺ concentration. Crystalline purity and phase identification was confirmed and revealed using powder X‐ray diffraction and Rietveld refinement analysis. The surface morphology of Zn_1‐xEu_xWO₄ (x = 0, 0.01, 0.02, 0.03, 0.04 and 0.05) was examined using scanning electron microscopy (SEM) techniques. From SEM analysis, the ZnWO₄:Eu³⁺ phosphor prepared at 1–3% molar Eu³⁺ concentrations exhibited a small pebble‐like morphology with a smooth surface. On increasing the molar concentration of Eu³⁺ to >3%, the pebble stone morphology disappeared and a large, smooth irregular polygon‐shaped granular‐like morphology was obtained. Of the higher mol% Eu³⁺, the 4% Eu³⁺‐doped ZnWO₄ showed the best photoluminescence properties with high intensity and sharp excitation at 395 and 464 nm, followed by red emission centred at 615 nm with excellent CIE coordinates (x = 0.58 and y = 0.41) in the core red region. Elemental composition and chemical state analysis were carried out for the 4% Eu³⁺‐doped ZnWO₄ phosphor using X‐ray photoelectron spectroscopy and energy dispersive X‐ray spectroscopy studies. Based on all the above analyses, the Eu³⁺‐doped ZnWO₄ phosphor was found to be a very efficient red‐emitting phosphor under near‐UV light as well as under visible light excitation and could be used for white LED and field emissive displays applications.     

Intensity of cooperative vibronic transitions in the Eu(III), Gd(III) and Tb(III) formates spectra

The luminescence and absorption spectra of the lanthanide ions in solids and coordination compounds are characterized by sharp pure electronic lines, which are accompanied by much weaker lines of vibronic transitions. The vibronic spectroscopy is a good probing tool for investigations of the properties of surrounding ion ligands. The lanthanides formates are efficient luminescent crystals and can be viewed as the elementary type in the whole class of the oxygen-containing lanthanide coordination compounds. The intensity of vibronic transitions in spectra of luminescence and excitation europium (⁵D₀→⁷F₂, ⁷F₀→⁵D₂), terbium (⁷F₆→⁵D₄), gadolinium (⁶P_7/2→⁸S_7/2) in anhydrous formates of the type Ln(HCOO)₃ (Ln = Eu, Tb, Gd) and Y(HCOO)₃.2H₂O doped with Eu³⁺ and Tb³⁺ (C ~1 mol%) are reported. Also, the infrared and Raman spectra were obtained for the same compounds. Related integral intensity vibronic sidebands depend on the type of electronic transition of the same ion and varies for the same electronic transitions in different crystals. The obtained experimental data referring to the rate constants of vibronic transitions and intensity distribution in vibronic spectra on normal vibrations of the formate groups are in agreement with the predictions based on the Stavola–Dexter theory of cooperative vibronic transitions.     

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.     

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.