Functioning Of EU Research Articles

Structure-Dopant Concentration Relations in Europium-Doped Yttrium Molybdate and Peak-Sharpening for Luminescence Temperature Sensing.

A set of Eu3+-doped molybdates, Y2-xEuxMo3O12 (x = 0.04; 0.16; 0.2; 0.4; 0.8; 1; 1.6; 2), was synthesized using a solid-state technique and their properties studied as a function of Eu3+ concentration. X-ray diffraction showed that the replacement of Y3+ with larger Eu3+ resulted in a transformation from orthorhombic (low doping concentrations) through tetragonal (high doping concentrations), reaching monoclinic structure for full replacement in Eu2Mo3O12. The intensity of typical Eu3+ red emission slightly increases in the orthorhombic structure then rises significantly with dopant concentration and has the highest value for the tetragonal Y2Mo3O12:80mol% Eu3+. Further, the complete substitution of Y3+ with Eu3+ in the case of monoclinic Eu2Mo3O12 leads to decreased emission intensity. Lifetime follows a similar trend; it is lower in the orthorhombic structure, reaching slightly higher values for the tetragonal structure and showing a strong decrease for monoclinic Eu2Mo3O12. Temperature-sensing properties of the sample with the highest red Eu3+ emission, Y2Mo3O12:80mol% Eu3+, were analyzed by the luminescence intensity ratio method. For the first time, the peak-sharpening algorithm was employed to separate overlapping peaks in luminescence thermometry, in contrast to the peak deconvolution method. The Sr (relative sensitivity) value of 2.8 % K-1 was obtained at room temperature.

Sensitive Luminescence Thermometry through Excitation Intensity Ratio in Eu-Doped BaTiO3.

Optical ratiometric thermometry techniques have gained much attention in recent years due to their reliable and noncontact temperature sensing capability for industrial and biorelated applications. Herein, we exploited the temperature dependence of the absorption band of BaTiO3 (BTO) for novel excitation intensity ratio (EIR) thermometry. Photoluminescence and excitation properties of Eu3+-doped BTO powders were studied as a function of Eu3+ doping concentration. The excitation peak intensities at 397 and 468 nm, corresponding to the 7F0 → 5L6 and 5D2 transitions of Eu3+, were used as EIR parameters. The temperature dependence of the EIR can be explained by the competitive absorption between Eu3+ and the BTO host. The EIR properties were studied in relation to the doping concentration, registering a maximum relative sensitivity (Sr) of 4.89% K-1 in BTO:Eu3+ (0.5%) at 303 K. An amphoteric Eu3+ occupation mode at both Ba2+ and Ti4+ sites was found to interpret the doping concentration dependence of the Sr. The reduced Ba2+ site occupation ratio proved to be responsible for the low Sr values at high Eu3+ doping concentrations. Accordingly, an Eu3+/Ti3+ codoping method was further proposed to improve the Sr by increasing the Ba2+ site occupation ratio. Our result showed that BTO:Eu3+ (0.5%) demonstrated an enhancement of Sr from 4.89 to 6.42% K-1 at 303 K after 2% Ti3+ codoping.

Synthesis and Structural Features of Tunable Emitting Single- Phased Eu3+/ Tb3+ Co- Doped LaAlO3 Nanophosphors

In the prevailing study, single- phased color- tunable La1-x-yEuxTbyAlO3 co- doped nanocrystalline phosphors have been synthesized via the most simplistic and low cost urea- aided solution combustion synthetic route. This was done by adjusting the doping concentration of Eu3+ (x = 0.01, 0.03, 0.05, 0.07 mol) and Tb3+ (y = 0.03 mol) ions in the LaAlO3 host lattice. The X- ray powder diffraction (XRD) and Rietveld refinement analysis confirmed the formation of single- phased La0.97-xAlO3: xEu3+/ 0.03Tb3+ (x = 0.07), co- doped nanophosphor at 800°C. The synthesized nanophosphors were crystallized in cubic crystal system having Pm3̄m space group with 221 space group number. The morphological studies i.e., field emission scanning electron microscopy (FE- SEM), and transmission electron microscope (TEM) images depicted the agglomerated clusters of distinct spherical shaped particles of La0.97-xAlO3: xEu3+/ 0.03Tb3+ in nano- regime. Energy dispersive X- ray analysis (EDAX) was employed to ascertain the real elemental mapping of the fabricated phosphors. Through diffuse reflectance (DR) spectroscopy measurements, the optical band gap value for La0.92Eu0.05Tb0.03AlO3 nanocrystalline phosphor was determined to be 5.26 eV. The photoluminescent excitation (PLE) and photoluminescent emission (PL) spectra were studied in detail as a function of Eu3+ ion contents and La1-x-0.03AlO3: xEu3+/ 0.03Tb3+ (x = 0.05 mol) co- doped sample exhibits strongest emission and over the 0.05 Eu3+ ions doping concentration, the emission intensity falls as a consequence of the quenching phenomenon. The concentration quenching in directed co- doped nanophosphors was attributed to the dipole - dipole interactions. With the exploitation of photoluminescent data, Commission International de I'Eclairage 1931 (CIE) color coordinates (x, y) of co- doped samples have been calculated from the emission spectra, which revealed the color could be tuned i.e., from orange to red region in La0.97-xAlO3: xEu3+/ 0.03Tb3+ samples with divergences in the Eu3+ and other significant photometric assets viz. correlated color temperature (CCT), color purity (CP) of the synthesized La1-x-yAlO3: xEu3+, yTb3+ co- doped nanocrystalline photoluminescent materials were also determined. The studies outcomes suggested that Eu3+/ Tb3+ co- doped LaAlO3 phosphors have great potential as color- tunable luminescent material in solid- state lighting and display technologies.

Correlation between the unit cell parameters and electronic transitions in Bi1-xEuxFeO3 thin films

Among AFeO3 (A being divalent or trivalent cation) perovskites, BiFeO3 (BFO) exhibits unique as well as complex electronic structure. In the present study local structure of BFO have been manipulated systematically and correlation with the electronic structure has been presented in detail. An electronic energy-level diagram of polycrystalline Bi1-xEuxFeO3 (0 ≤ x ≤ 0.225) has been presented. Using detailed quantitative structural analysis, diffuse reflectance spectrum and the Kubelka-Munk model, the effect of local structural modification on the electronic structure has been investigated. Systematic structural modification has been achieved by Eu3+ substitution which affects bond length, bond angle, and octahedral rotation, consequently, drives the system towards a higher symmetry configuration. Changes in the multiple electronic transitions in pure BFO thin films as a function of Eu3+ substitution have been investigated in detail. An additional change is the emergence of the 4f levels of the rare earth substituent in the valence and conduction bands, Charge-transfer, and doubly degenerated d-d transitions (6A1g→4T2g and 6A1g→4T1g) have been traced as a function of local changes at the unit cell level. In centrosymmetric configuration, 6A1g→4T1g electronic transition is found to be forbidden by the Laporte Rule.

Trivalent rare-earth-codoped silicate phosphor materials (Ba1.3Ca0.7−x−y SiO4: xDy3+/yEu3+) for solid-state lighting

Trivalent dysprosium/europium-codoped silicate phosphors (Ba1.3Ca0.7x−y SiO4: xDy3+/yEu3+) were prepared as a function of Eu3+ concentration (x = 0.03 and y = 0.01–0.05). The phosphors showed the averaged crystallite size of ∼37.2 ± 1.3 nm and displayed nano-/micro-scale grains with some void defects. The energy bandgap is about 4.3 eV for co-doped samples and 3.2 eV for the silicate host. The photoluminescence spectra indicated that the presence of Eu3+ ions enhanced the red light emission, and the emission peaks located at the versatile wavelengths of 482, 577, 592, 614, 652, and 703 nm. Then, the internal quantum efficiencies were estimated by using the Judd–Ofelt model. Resultantly, the best quantum efficiency was ∼74% when the doping concentrations were 3 mol% Dy3+ and 4 mol% Eu3+ ions. Finally, the CIE coordinate data exhibited that the emission color could be tuned from white to reddish-orange by changing the Eu3+ contents, proposing the applicability of Ba1.3Ca0.7−x−y SiO4:xDy3+/yEu3+ phosphors to the solid-state lighting.

Dazzling Red-Emitting Europium(III) Ion-Doped Ca2LaHf2Al3O12 Garnet-Type Phosphor Materials with Potential Application in Solid-State White Lighting.

Bright red-emitting phosphors with high color purity and high photoluminescence quantum yield (PLQY) are highly demanded for the fabrication of high-performance warm-white light-emitting diodes (LEDs). Herein, we demonstrated a novel efficient Eu3+-activated Ca2LaHf2Al3O12 garnet phosphor with excellent luminescence properties for near-ultraviolet (near-UV) excited warm-white LEDs. The Ca2LaHf2Al3O12:Eu3+ phosphors exhibited an intense excitation spectrum in the near-UV region with a maximum around 394 nm, and they produced dazzling red luminescence peaking at 592, 614, 659, and 711 nm due to the 5D0 → 7FJ (J = 1-4) transitions of Eu3+ ions when the excitation wavelength was set at 394 nm. Luminescent properties have been studied as a function of Eu3+ doping concentration, and the highest emission intensity was achieved at 50 mol % Eu3+, while the dipole-dipole interaction brought the concentration quenching effect. The Ca2LaHf2Al3O12:50%Eu3+ sample exhibited CIE chromaticity coordinates of (0.6419, 0.3575) with a color purity of 92.7%, and its PLQY was measured to be 64%. The thermal stability and activation energy of Ca2LaHf2Al3O12:50%Eu3+ phosphors were also discussed and analyzed. Finally, we made a near-UV chip-based white LED device in which the Ca2LaHf2Al3O12:50%Eu3+ phosphor was utilized as a red ingredient. A bright warm-white light emission was realized from this LED device under 80 mA driving current, accompanied by a high color rendering index (CRI) of 88.3, a low correlation color temperature of 3853 K, and good CIE chromaticity coordinates of (0.3909, 0.3934). These results revealed that these red-emitting Ca2LaHf2Al3O12:Eu3+ phosphors have promising application prospect in near-UV-excited warm-white LEDs with high a CRI.

Efficacy of Eu3+ on improving the near–infrared optical nonlinearities and optical limiting properties of antimony sodium borate glasses

Efficacy of Eu3+ ions nonlinear optical and optical limiting performances of antimony sodium borate gasses was investigated and discussed in detail. Nonlinear optical absorption and refraction features were evaluated in open and closed aperture Z–scan modes, respectively. The open aperture Z–scan profiles of the glasses demonstrated a reverse saturable absorption behaviour attributed to two photon absorption. The closed aperture Z–scan profiles exhibited positive type nonlinear refraction due to self–focusing effect. The two photon absorption coefficients demonstrated an increasing trend while the optical limiting threshold values demonstrated a decreasing trend as the function of Eu3+ concentration in the composition. This improved two photon absorption and decreased OL threshold coefficients with respect to Eu2O3 concentration in the compositions endorse the glasses as contending materials for the fabrication of optical limiters, which are promising use for protection of eyes and other sensitive instruments from laser induced damages.

Synthesis and characterization of Eu3+ doped TiO2 thin films deposited by spray pyrolysis technique for photocatalytic application

In this study, nanocrystalline TiO2: Eu3+ thin films are successfully formed by spray pyrolysis technique deposited on glass substrate. Structure, optical, electrical, surface morphology, and photocatalytic degradation of Methylene blue have been examined. The XRD analysis illustrate the tetragonal crystal structure of films with anatase phase and reduces crystallite size linearly with increasing Eu3+ concentration. The optical properties of the films are analyzed using transmittance and reflectance spectra, which are measured using UV–vis-NIR double-beam spectrophotometer. Optical properties such as refractive index (n), extinction coefficient (k), optical conductivity (σ) and Urbach energy (Eu) have been calculated as a function of Eu3+ concentration. Film thickness were evaluated using the refractive index dependence on wavelength. The films thickness were determined as 97.13, 122.62, 123.24, 117.14 and 128.25 nm, respectively, for Eu doped TiO2 at 0,4, 6, 8 and 10 wt % doping concentration. The band gap values raised from 3.29 to 3.42 eV with increasing the Eu3+ dopant concentration. The highest electrical conductivity was found to be 3.01 × 10−2(Ω·cm)−1 at high doping level with 10 wt% Eu3+. Scanning electron microscopy (SEM) analysis indicated consistent allocation of irregular and spherical shaped grains covering the substrate surface. The average grain size in range of 82.5—51.1 nm is observed and films show porous nature. The photocatalytic effect of TiO2: Eu3+ thin films is predicted from the degradation of methylene blue (MB) at room temperature under UV light irradiation. An enhancement in photocatalytic degradation observed by increasing the amount of Eu3+ due to increase in the (electron-hole) pair production and increase of film thickness. These results make TiO2: Eu3+ thin films as attractive candidate for photovoltaic cells and other optoelectronic device applications.

Effect of Eu3+ doping concentration on the structural and luminescence properties of NaYF4: Eu3+ nanoparticles

In our study, hexagonal-NaYF4: Eu3+ nanoparticles were synthesized by the solvothermal method at 180◦C for 24 hours. The typical vibrational spectrum showed the appearance of characteristic organic modes of oleic acid in the sample. The presence of elements such as Na, Y, F and Eu was indicated in the energy-dispersive X-ray spectroscopy (EDX). X-ray diffraction (XRD) patterns revealed that the NaYF4 host possessed the hexagonal structure when the doping contents below 5 mol%. At the Eu3+ amount of 10 mol%, the XRD appeared additional peaks of cubic phase of NaYF4 host. Both XRD and TEM data showed that the crystal sizes increase slightly as a function of Eu3+ doping concentration. Under an excitation at 395 nm, photoluminescence (PL) spectra revealed that the ratio of emission intensity between orange and red were controlled by changing the doping concentration. The optimal doping concentration was about 7 mol% for achieving the highest emission intensity. Moreover, PL data also demonstrated that a part of ions Eu3+ could occupy at Y3+ sites in the crystal structure of NaYF4. Because of their outstanding luminescent properties, NaYF4:Eu nanoparticles would the potential material for applications in biomedical medicine, optoelectronics.

Effect of the Eu3+-Sn4+ substitution on the structural and optical properties of SnO2:Eu3+

SnO2 nanocrystals with an average partiaxsxddccle size around 50 nm were prepared by using hydrothermal method. X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) data show that the doping of Eu3+ with concentrations ranging from 0 to 2 mol% resulted in a slight decrease of size from 50 to 35 nm. The High Resolution Transmittance Electron Microscopy (HRTEM) results of 1 mol% doping sample provide that the crystals size is around 38 nm and the interplanar spacing is 0.34 nm characterized for (110) planes of SnO2. Moreover, the peak shape and relative intensity of Eu3+ emission upon a direct and indirect excitation indicate the presence of two sites around Eu3+ ions, that are in the D2h sites of SnO2 and on the surface of nanocrystals. The Eu3+ ions located in different sites are selectivity excited. An optimizing of synthesis parameters can promote the incorporation of Eu3+ ions in SnO2 crystal lattice. Specially, the doping leads to the growth of crystallites along (101) preferred plane. The competition between red and orange emission as a function of Eu3+ contents was also considered. Under indirect excitation, the asymmetric ratio between 5D0-7F2 and 5D0-7F1 transitions of Eu3+ ions is unaltered at 0.3 in the range of Eu concentrations from 0.5 to 2 mol% achieved for the first time. PL spectra and decay measurements give evidence about the strong energy transfer between SnO2 and Eu3+ ions.

Synthesis of GdBO3:Eu3+ nanophosphors via acetylacetone assisted aqueous sol–gel route: Effect of some synthesis parameters

Abstract Nano-sized Eu3+ -doped GdBO3 vaterite type nanophosphors have been synthesized successfully via acetylacetone assisted aqueous sol–gel route. Systematic investigation of the influence of Eu3+ ion content and pH value of the suspension of precursors on structural, morphological and luminescence spectroscopic properties has been performed. X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, field emission-scanning electron microscopy (FE-SEM), Thermogravimetric and differential thermal gravimetry (TG/DTA), room temperature steady and time resolved photoluminescence (PL) spectroscopy techniques were employed to characterize the obtained powder samples. It has been found that the Eu3+ ion content and pH value precursors suspension have important effect on the structural, morphology and emission properties. The XRD analysis reveals that GdBO3: 10% mol Eu3+ synthesized at pH = 2 and pH = 10 exhibit the quasi-purest P63/mmc vaterite structure. The vibrational absorption of (BO3)3- group is assigned to the GdBO3 with calcite type or other vaterite structure namely triclinic and monoclinic. The morphologies of GdBO3 particles size increases with increasing of pH value. All sample present only the orange-red colors emission from 5D0 levels to the 7FJ levels (J = 0–3) of Eu3+ ion. Furthermore, it was found that 10% concentration of Eu3+ presents the quenching of emission in GdBO3. Also, it was that the emission intensity was affected by the pH value and sample with pH = 10 exhibits the highest emission intensity. The asymmetry ratio parameter R between red and orange emission intensities in function of Eu3+ content and pH value is determinate and discussed.

Photoluminescence properties of the material based on SiO2–Y2O3:Eu3+,Tb3+ under different in situ temperature prepared by the sol-gel process

The codoped SiO2–Y2O3:Tb3+,Eu3+ (xTb: 1.0 mol%; xEu: 0.1; 0.2; 0.5; 0.7 and 1.0 mol%) nanomaterials were prepared at room temperature by sol-gel process and heat treated at 900 and 1000 °C during 4 h, under air atmosphere. The materials were characterized by X-ray powder diffraction (XRD) and UV excited photoluminescence. The material exhibits Y2O3 cubic, one peak positioned around 26° assigned to the cristobalite SiO2 phase and amorphous SiO2 phases due to the Y2O3 and SiO2 presences. The emission bands observed in the emission spectra under excitation at 301 are assigned to the Tb3+ and Eu3+ ions, with clear evidence of energy transfer from Tb3+ to Eu3+. The line assigned to the 5D0→7F2 transition (Eu3+) increase the intensity as a function of Eu3+ concentration. The sensibility under controlled temperature variation was investigate. The Eu3+: 0.5 mol% doped material (annealed @900 °C) exhibited higher thermic sensitivity (with maximum relative sensitivity 0.294% K−1 in 303 K). Under excitation at 395 nm, the red color emission increases the intensity due the thermal treatment. Furthermore, CIE parameters and the color correlated temperature (CCT) are discussed in order to characterize the greenish color emission. Based on the results, these luminescence materials may be potential candidates for optical thermometry diodes, solid-state lighting and nano in vivo biological system.

Luminescence properties of a novel red phosphor 6LaPO4 -3La3 PO7 -2La7 P3 O18 :Eu3.

Eu3+ -doped 6LaPO4 -3La3 PO7 -2La7 P3 O18 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 (3.00-6.00mol%). Excitation spectra of 6LaPO4 -3La3 PO7 -2La7 P3 O18 :Eu3+ showed strong absorption bands at 280, 395, and 466nm, while the luminescence spectra exhibited prominent red emission peak centred at 615nm (5 D0 →7 F2 ) in the red region. CIE chromaticity coordinates of the 6LaPO4 -3La3 PO7 -2La7 P3 O18 :5%Eu3+ phosphor were (0.668, 0.313) in the red region, and defined its potential application as a red phosphor.

Multicolor and Warm White Emissions with a High Color Rendering Index in a Tb3+/Eu3+-Codoped Phosphor Ceramic Plate.

A series of Tb3+/Eu3+-codoped phosphor ceramic plates with a high color rendering index (CRI) for a near-ultraviolet light emitting diode (LED) were fabricated. Color emission can be tuned from green to reddish as a function of Eu3+ concentration. By doping only 0.15 mol% of Eu3+ concentration, a comfortable warm white emission is promoted as a result of simultaneous emissions of Tb3+ and Eu3+ ions. A theoretical model is proposed to calculate the contributions of the emitted color of the donor (Tb3+) and acceptor (Eu3+) ions in terms of europium concentration. The energy transfer from Tb3+ to Eu3+ ions is corroborated by the luminescence spectra and decay time of Tb3+, with a maximum energy transfer efficiency of 76% for 28 mol% of Tb3+ and 14 mol% of Eu3+. Warm white LEDs were constructed using a 380 nm UV chip and showed a CRI of 82.5, which was one of highest values reported for Tb3+/Eu3+-codoped samples. Color-correlated temperature (CCT), color coordinate (CC), and luminous efficacy (LE) were utilized to know the potentials as a phosphor converter in solid-state lighting.

Energy-transfer Er3+ to Eu3+ and frequency upconversion visible emission in PbGeO3:PbF2:CdF2 glass

Er3+ to Eu3+ energy-transfer and frequency upconversion in PbGeO3:PbF2:CdF2 glass are reported. Emission spectra excited at 980 nm was obtained for Er3+-doped samples, while Eu3+ emissions only occurred for double-doped (Er3+/Eu3+) or triple-doped (Yb3+/Er3+/Eu3+) samples. Codoped samples’ spectra exhibit bands around 520 (2H11/2 – 4I15/2), 545 (4S3/2 – 4I15/2), 590 (5D0 – 7F1), 610 (5D0 – 7F2), 660 (4F9/2 – 4I15/2) and 700 (5D0 – 7F4) nm. The Er3+ green emissions’ lifetimes were examined as a function of Eu3+ content evidencing Er3+-to-Eu3+ energy-transfer. The addition of Yb3+ enhanced the Eu3+ ions’ emissions suggesting potential application for upconversion-based white light phosphor.

Photoluminescent properties and Judd-Ofelt analysis of Eu3+-doped NaMg(PO3)3 red phosphor

A series of novel red-emitting Na1-xMg(PO3)3: xEu3+ phosphors were successfully synthesized using the high-temperature solid-state method. The crystal structure, photoluminescence spectra, decay lifetime and quantum efficiency of the phosphors were investigated as a function of Eu3+ concentration. A dominant red emission peak centered at 612 nm along with an intense 5D0→7F4 transition at 699 nm indicates that Eu3+ occupies low symmetry sites in NaMg(PO3)3 host lattice, which was confirmed by Judd-Ofelt analysis. The crystallographic site-occupations of Eu3+ were investigated by the site-selective excitation and emission spectra in the 5D0→7F0 region, which indicates that Eu3+ ion in NaMg(PO3)3 prefers to occupy the crystallographic site of C3 symmetry. The emission intensity is closely dependent on Eu3+ concentration with critical concentration of 8 mol%. NaMg(PO3)3: Eu3+ phosphor exhibits good thermal stability (67.2% at 473 K).

A novel dazzling Eu3+‐doped whitlockite‐type phosphate red‐emitting phosphor for white light‐emitting diodes

AbstractA series of novel red‐emitting Ca8ZnLa1−xEux(PO4)7 phosphors were successfully synthesized using the high‐temperature solid‐state reaction method. The crystal structure, photoluminescence spectra, thermal stability, and quantum efficiency of the phosphors were investigated as a function of Eu3+ concentration. Detailed analysis of their structural properties revealed that all the phosphors could be assigned as whitlockite‐type β‐Ca3(PO4)2 structures. Both the PL emission spectra and decay curves suggest that emission intensity is largely dependent on Eu3+ concentration, with no quenching as the Eu3+ concentration approaches 100%. A dominant red emission band centered at 611 nm indicates that Eu3+ occupies a low symmetry sites within the Ca8ZnLa(PO4)7 host lattice, which was confirm by Judd‐Ofelt theory. Ca8ZnLa1−xEux(PO4)7 phosphors exhibited good color coordinates (0.6516, 0.3480), high color purity (~96.3%), and high quantum efficiency (~78%). Temperature‐dependent emission spectra showed that the phosphors possessed good thermal stability. A white light‐emitting diode (LED) device were fabricated by integrating a mixture of obtained phosphors, commercial green‐emitting and blue‐emitting phosphors into a near‐ultraviolet LED chip. The fabricated white LED device emits glaring white light with high color rendering index (83.9) and proper correlated color temperature (5570 K). These results demonstrate that the Ca8ZnLa1−xEux(PO4)7 phosphors are a promising candidate for solid‐state lighting.

Photoluminescence properties of novel Ba2Lu5B5O17:Eu3+ red emitting phosphors with high color purity for near-UV excited white light emitting diodes.

A series of new red-emitting Ba2Lu4.98−xEuxLa0.02B5O17 (0.1 ≤ x ≤ 1.0) phosphors were synthesized via the high-temperature solid-state reaction method. The phase formation of the as-synthesized Ba2Lu4.48Eu0.5La0.02B5O17 phosphor was confirmed by powder X-ray diffraction analysis. It was found that La3+ doping resulted in the reduction of LuBO3 impurities and thus pure phase Ba2Lu5B5O17 was realised. The morphology of Ba2Lu4.48Eu0.5La0.02B5O17 phosphors was studied by field emission scanning electron microscopy (FE-SEM). As a function of Eu3+ concentration the photoluminescence spectra and decay lifetimes were investigated in detail. Under excitation at 396 nm, a dominant red emission peak located at 616 nm (5D0 → 7F2) indicated that Eu3+ ions mainly occupied low symmetry sites with a non-inversion center in Ba2Lu4.48Eu0.5La0.02B5O17. The optimal Eu3+ ion concentration was found to be x = 0.5 and the critical distance of Eu3+ was determined to be 6.55 Å. In addition, the concentration quenching takes place via dipole–dipole interactions. The phosphors exhibited good CIE (Commission International de I'Eclairage) color coordinates (x = 0.643, y = 0.356) situated in the red region and a high color purity of 97.8%. Furthermore, the internal quantum efficiency and the thermal stability of Ba2Lu4.48Eu0.5La0.02B5O17 phosphors were also investigated systematically. The results suggest that Ba2Lu4.48Eu0.5La0.02B5O17 may be a potential red phosphor for white light-emitting diodes.

Charge transfer transition and energy transfer in Eu3+-doped Gd10V2O20

Eu3+-doped Gd10(1-x)Eu10xV2O20 (x = 0 – 1) phosphors were synthesized via the sol-gel process. The formation of a single phase compound was verified through the X-ray diffraction studies. Luminescence properties of Gd10V2O20:Eu3+ are investigated by optical and laser excitation spectroscopy. The emission and excitation spectra, luminescence decays were measured in the temperature region 7–300K. The strong emission due to the vanadate group of Gd10V2O20:Eu3+ is observed at low temperature. The charge transfer transition of Eu3+ depends strongly on the Eu3+-concentration in Gd10V2O20:Eu3+. The emission intensity as a function of Eu3+ concentration under excitation of charge transfer band is inconsistent with that of the 4f7 states (the 5L6 state) of Eu3+. The energy transfer occurs between two Eu3+ ions at low Eu3+ concentration (< 10mol%), while energy diffusion dominates at high Eu3+ concentration.

Spectroscopic investigation on europium doped heavy metal borate glasses for red luminescent application

The present study explores a new borate family glasses based on 10ZnO–5Na2O–10Bi2O3–(75 − x) B2O3–xEu2O3 (x = 0, 0.1, 0.5, 1, 1.5, 2, 3 mol%) composition, synthesized by rapid melt quench technique. Prepared glasses were subjected to the density and refractive index measurements and their values were used to calculate other physical properties of the glass matrix as a function of Eu3+ concentration. XRD confirmed amorphous nature of the glasses. FTIR spectra in the absorption mode were recorded in the 400–4000 cm−1 region to identify different functional groups in the glass matrix. Deconvoluted FTIR spectra showed increase in BO4 units with rise in europium content which confirmed the ‘network strengthener’ role of europium ions by creating bridging oxygens (BOs). Optical properties were investigated for their luminescence behavior through various spectroscopic techniques such as UV–Vis–NIR absorption, excitation, emission, decay profiles, and color measurements at room temperature. Lasing properties of the glasses like total radiative life time, branching ratio, emission cross section, and optical gain were obtained from the calculated Judd–Ofelt (Ω2,Ω4) intensity parameters. From the measured values of emission, cross sections, branching ratios, life times, strong photoluminescence features, and CIE chromaticity coordinates, 0.5 mol% of Eu3+ ions doped ZnNaBiB glasses showed optimum performance and are potential candidate for red light generation at 613 nm.