Concentration Of Europium Ions Research Articles

Spectral-luminescence characteristics of solid solutions ZrO2-Eu2O3 crystals

Data on the structure of (100-x) mol.% ZrO2 - х mol.% Eu2O3 solid solution concentration series (x = 4, 6, 8, 10, 12, 15, 20, 27) have been presented. The crystals with x = 4 have a hexagonal structure, while those with x = 8 are a mixture of cubic and tetragonal phases. The crystals with x = 10, 12 and 15 have a cubic structure, and those with x = 27 are two-phase and contain cubic modification and pyrochlore phase.Luminescent spectra of the (100-x) mol.% ZrO2 - х mol.% Eu2O3 solid solutions have been taken in the as-grown and air-annealed states. The presence of Eu2+ ions was revealed in (100-x) mol.% ZrO2 - х mol.% Eu2O3 solid solution concentration series (x = 4, 6, 8, 10, 12, 15, 20, 27) after growth, the content of which decreases significantly after heat treatment in air. It has been shown that in (96-85) mol.% ZrO2 - (4–15) mol.% Eu2O3 crystals the relative proportion of optical centers of Eu3+ surrounded by oxygen seven-vertex is lower compared to crystals (96.7–85) mol.% ZrO2 - (3.6–15) mol.% Gd2O3 - 0.1 mol.% Eu2O3. The (73, 80) mol.% ZrO2 - (20, 27) mol.% Eu2O3 crystals contain optical centers of Eu3+ surrounded by oxygen six-vertex with two oxygen vacancies along the diagonal faces of the cubic crystal lattice. Their percentage being higher than in the (79.9, 76.9) mol.% ZrO2 - (20, 33) mol.% Gd2O3 - 0.1 mol.% Eu2O3 crystals.In crystals of (100-x) mol.% ZrO2 - х mol.% Eu2O3 solid solution concentration series (x = 4, 6, 8, 10, 12, 15, 20, 27), the presence of concentration quenching was revealed with increasing concentration of europium ions.

Physical and Luminescence Properties of Europium Ions Doped Barium Tellurite Glass

Barium tellurite (Ba-Te) base glass with and without europium ions have been synthesized by customary melting and quenching method. XRD is done for the verification of the nature of prepared specimens. DSC of the samples was done to determine the glass transition temperature. Density (ρ) of specimens was calculated by Archimedes’s principle. Other physical parameters as oxygen packing density (OPD), Europium ion concentration (CL) in the specimen, molar volume (Vm), intermolecular distance Ri, Polaron radius Rp, europium ion concentration and Molar index of refraction Rm, were computed. In order to study the optical characteristics of the specimens, for instance, coefficient of absorption, forbidden energy gap (Eg), refractive index, and Urbach Energy (E), UV-visible absorption characterizations of Ba-Te glasses was performed in the range of 340-1000 nm. PL characterization has performed for photoluminescence study.

Doped lanthanum cerate pyrochlore for multicolor luminescent phosphor: Decisive role of energy transfer and defects

Designing of efficient luminescent materials requires proper understanding of energy transfer, defect evolution and dopant local structure. The present work is a perfect amalgam wherein we have thoroughly investigated the concentration dependent host sensitized energy transfer, defect evolution and local structure of europium ion in La2Ce2O7 (LCO) pyrochlore material. Raman spectroscopy suggested stabilization of defect fluorite structure for LCO as well as LCO:Eu3+ (LCOE) but degree of structural distortion as well as oxygen vacancies (OVs) increases with increase in europium ion concentration. Diffuse reflectance spectroscopy suggested band gap narrowing at higher doping level owing to enhanced density of OVs. Positron annihilation lifetime spectroscopy suggested an increase in the formation of oxygen vacancies and vacancy clusters near the surfaces at higher doping. As a result, LCO, on irradiation with 250 nm ultraviolet photon showed visible emission due to OVs as well charge transfer transition. On Eu3+ doping emission spectra was rich in host as well as europium emission and host to europium energy transfer increases with increase in europium ion concentration. This get's reflected as violet blue emission at lower doping and yellowish white at higher doping level ≥7.5% under host excitation and orange-red emission under 471 nm dopant excitation. Europium ion emission spectral profiles in LCOE suggested stabilization of Eu3+ in CeO6 octahedra as is also confirmed using lifetime spectroscopy. Judd-Ofelt measurement further reflected higher branching ratio for 5D0→7F2, internal quantum yield ~48% and high Ω2 compared to Ω4. This work highlights the importance of local dopant site, HSET, excitation photon and defects in designing color tunable luminescent materials and is expected to play an important role in designing the phosphor converted light emitting diodes (pc-LEDs).

Development of novel Na2Mg3Zn2Si12O30:Eu3+ red phosphor for white light emitting diodes

A novel Eu3+ activated Na2Mg3Zn2Si12O30 red emitting phosphor was synthesized by solid state reaction at ambient conditions. The phase formation of prepared samples were confirmed by powder X-ray diffraction (XRD) and their luminescent properties were studied by photoluminescence(PL) spectroscopy. The surface morphology of samples were studied using SEM technique. The XRD profile of prepared samples are well matched with JCPDS card no(48–0418). The crystallite size is calculated using Scherrer's formula and found to be 0.5623 μm. The PL emission spectra shows intense peak around 614 nm arising as a result of electric dipole transition upon 394 nm excitation. The influence of increasing europium ion concentration on photoluminescence emission intensity were also studied. It is observed that PL intensity initially increases up to 11 mol% Eu3+ and then decreases. The concentration quenching is due to dipole-dipole interaction. Further, the commission International del’Eclairagethe (CIE) chromaticity coordinates, CCT and color purity for optimized Na2Mg3Zn2Si12O30:Eu3+(11 mol%) are calculated for 394 nm excitation and found to be (0.6391,0.3592), 1110K and 99.6% respectively. Moreover Eu3+activated Na2Mg3Zn2Si12O30 shows good thermal stability having activation energy 0.258eV. All the above results reveal that Na2Mg3Zn2Si12O30 doped Eu3+ can serve as potential candidates for red phosphor of WLED applications.

Co-emission and energy transfer of Sm3+ and/or Eu3+ activated zinc-germanate- tellurite glass as a potential tunable orange to reddish-orange phosphor

Sm3+/Eu3+ single doped and co-doped zinc-germanate-tellurite glasses were prepared by the glass melting method. Raman and optical spectroscopic properties of Sm3+, Eu3+ and Sm3+/Eu3+ doped TeO2-GeO2-ZnO glasses have been characterized through optical absorption and pulsed/steady fluorescence. Excitation and emission spectra measurements indicated that the energy transfer process Sm → Eu is active in the samples. The concentration of europium ions was varied to provide red emission for possible control over the chromaticity tuning in the red-orange region. Upon 344 nm excitation, the color of the global emission can be adjusted from orange of 2038 K to reddish-orange of 1683 K by increasing the Eu3+ content from 1 up to 2% mol, and co-doped with 0.5% mol Sm3+. Reddish-orange color purity very close to 100% is attained when the phosphors are excited at 406 nm. The time shortening of Sm3+ emission decay in the presence of Eu3+ was attributed to a Sm3+ → Eu3+ non-radiative energy transfer process. From fitting the Sm3+ emission decay profile with the Inokuti-Hirayama model, it was inferred that the energy transfer process could be dominated by an electric dipole-dipole interaction.

Photoluminescent and structural properties of color tunable trivalent europium doped SrGdAlO4 nanophosphors

A series of Eu3+ ion doped SrGdAlO4 nanophosphors were prepared via solution combustion technique utilizing urea as a fuel. Structural properties of the tetragonal phase of the host/doped lattice belonging to the space group I4/mmm were characterized by powder X-ray diffraction (PXRD). Photoluminescence spectra, decay curves, UV–Visible diffuse reflectance spectra (UV–Vis DRS) and Judd–Ofelt analysis were utilized to characterize the photoluminescent properties. The radiative rates (Ar), branching ratios (Br) and intensity parameters (Ωλ) were estimated by Judd–Ofelt analysis. The optimal doping concentration of europium ions for SrGdAlO4 host lattice was found to be 20 mol%, above which concentration quenching was observed due to dipole–dipole interactions. CIE coordinates values lie in the blue region at lower concentrations of Eu3+ ions, which shifted towards white and then to reddish-orange region with higher concentrations of Eu3+ ions, suggesting the color tunable property of the synthesized nanophosphors. Lower value of CCT and color tunable phenomenon proved it as potential candidate for warm white light and phosphor converted white light emitting diodes (Pc-WLEDs) applications. The optical band gap of both host lattice (5.50 eV) as well as of 20 mol% Eu3+ doped SrGdAlO4 nanophosphors (5.26 eV) lie in the range of semiconductors which enhanced their areas of applications.

Evaluation of a novel PVC-based efficient potentiometric sensor containing a tripodal diglycolamide (TREN-DGA) ionophore for europium(III) estimation

Polymeric membrane-based electrodes containing a multiple diglycolamide (DGA), such as a N-pivot diglycolamide (diglycolamide-TREN (TREN-DGA) and a C-pivot diglycolamide (tripodal diglycolamide) (T-DGA) as ionophore, and polyvinyl chloride (PVC) as the base polymer were fabricated. These membranes were tested for the potentiometric determination of europium ions in acidic feed solutions. The membrane with a composition of 81.5% PVC and 18.5% TREN-DGA showed a wide dynamic range (3.2 × 10−7 to 1.0 × 10−2 M) with a slope of 17.2 ± 0.4 mV per decade for europium ion. The presence of sodium tetraphenyl borate (NaTPB) as ionic additive in the DGA-TREN containing membrane marginally improved the dynamic range in the detection of europium ion. On the other hand, the membrane with a composition of 77.3% PVC and 22.7% T-DGA does not show any systematic potential response against variation of the concentration of europium ions in the external solution containing 1 M HNO3. The physical characterization of these membranes was carried out using techniques such as thermogravimetry (TGA), Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) in order to understand the effect of the different constituents of the membrane on the potential response for europium ion. AFM measurements revealed that the morphology of the membrane remained intact even after prolonged use of the membrane. The interference effect of Ca2+, Mg2+, Cu2+, Fe3+, Bi3+, Zn2+, Cd2+ and UO22+ on the potential response was investigated. The response time of the proposed sensor was found to be less than five seconds. The lifetime of the sensor electrode was found to be three months under proper storing conditions. The membrane sensor was employed in the determination of Eu3+ in synthetic water samples.

Influence of europium (Eu3+) ions on the optical properties of lithium zinc phosphate glasses

Europium doped lithium zinc phosphate glasses with composition xEu2O3-(15-x) Li2O-45ZnO-40P2O5 (where x=0, 0.1, 0.3 and 0.5 mol %) named as EP0, EP1, EP3 and EP5 respectively, are prepared by melt-quenching method and the influence of Eu3+ ions on physical and optical properties of these glasses has been studied. Optical properties were studied using optical absorption spectra which was recorded at room temperature in the UV-Visible region. Optical direct band gap and indirect band gap energies were measured and their values range from 3.167 to 4.23eV and 2.08 to 3.02eV, respectively. Refractive indices have been measured with respect to different concentration of europium ions. Fluorescence spectroscopy measurements have been performed by excitation in the UV-Visible range, which resulted in the significant fluorescence peaks. The luminescence color of the glass system is characterized using Commission International de l’Eclairage de France 1931 standards.

Role of Synthesis Method on Luminescence Properties of Europium(II, III) Ions in β-Ca2SiO4: Probing Local Site and Structure.

The europium ion probes the symmetry disorder in the crystal structure, although the distortion due to charge compensation in the case of aliovalent dopant remains interesting, especially preparation involves low and high temperatures. This work studies the preparation of the β-Ca2SiO4 (from here on C2S) particle from Pechini (C2SP) and hydrothermal (C2SH) methods, and its luminescence variance upon doping with Eu2+ and Eu3+ ions. The blue shift of the charge-transfer band (CTB) in the excitation spectra indicates a larger Eu3+-O2- distance in Eu3+ doped C2SH. The changes in vibrational frequencies due to stretching and bending vibrations in the FTIR and the Raman spectra and binding energy shift in the XPS analysis confirmed the distorted SiO44- tetrahedra in C2SH. The high hydrothermal temperature and pressure produce distortion, which leads to symmetry lowering although doping of aliovalent ion may slightly change the position of the Ca atoms. The increasing asymmetry ratio value from C2SP to C2SH clearly indicates that the europium ion stabilized in a more distorted geometry. It is also supported by Judd-Ofelt analysis. The concentration quenching and site-occupancy of Eu3+ ions in two nonequivalent sites of C2S were discussed. The charge state and concentration of europium ions in C2SP and C2SH were determined using X-ray photoelectron spectroscopy measurements. The C2S particles were studied by X-ray powder diffraction, FTIR, Raman, BET surface area, TGA/DTA, electron microscopy, XPS, and luminescence spectroscopy. The impact of citrate ion on the morphology and particle size of C2SH has been hypothesized on the basis of the microscopy images. This study provides insights that are needed for further understanding the structure of C2S and thereby improves the applications in optical and biomedical areas and cement hydration.

Multichannel Luminescence Properties of Mixed-Valent Eu2+/Eu3+ Coactivated SrAl3BO7 Nanocrystalline Phosphors for Near-UV LEDs.

Up to now, orchestrating the coexistence of Eu2+ and Eu3+ activators in a single host lattice has been an extremely difficult task, especially for the appearance of the characteristic emission of Eu2+ and Eu3+ in order to generate white light. Nevertheless, here we demonstrate a new Eu2+/Eu3+ coactivated SrAl3BO7 nanocrystalline phosphor with abundant and excellent multichannel luminescence properties. A series of Eu2+/Eu3+ coactivated SrAl3BO7 nanocrystalline phosphors were prepared through a Pechini-type sol-gel method followed by a reduction process. With excitation of UV/NUV light, the prepared SrAl3BO7:Eu2+,Eu3+ phosphors show not only the characteristic f-f transitions of Eu3+ ion (5DJ → 7FJ,J', J, J' = 0-3), but also the 5d → 4f transitions of Eu2+ ion with comparable intensity from 400 to 700 nm in the whole visible spectral region. The luminescence color of the SrAl3BO7:Eu2+,Eu3+ phosphor can be tuned from blue, blue-green, white, and orange to orange-red by changing the excitation wavelength, the overall doping concentration of europium ions (Eu2+, Eu3+), and the relative ratio of Eu2+ to Eu3+ ions to some extent. A single-phase white-light emission has been realized in SrAl3BO7:Eu2+,Eu3+ phosphor. The obtained SrAl3BO7:Eu2+,Eu3+ phosphor has potential application in the area of NUV white-light-emitting diodes.

Photoluminescence in europium ion–substituted bismuth niobate particles

ABSTRACTIn order to understand the influence of the substitution of europium ion for bismuth ion in the structural and photoluminescence properties of bismuth niobate, bismuth niobate ceramic powders, with different amount of europium ion, were prepared using sol–gel citrate route. The structural and morphological studies were made with X-ray diffraction, Raman, and scanning electron microscopy measurements. Rietveld’s analysis of X-ray diffraction proves the formation and increment of europium niobate phase in europium ion–substituted bismuth niobate samples with increase of europium ion concentration. Photoluminescence results also concur to that of X-ray diffraction and Raman with gradual swapping of europium ion emission from one phase to the other phase at higher concentration.

Effect of europium ion concentration on the structural and photoluminescence properties of novel Li2BaZrO4: Eu3+ nanocrystals

This work reports the influence of Eu3+ ion concentration on the structure and photoluminescence properties of Li2BaZrO4 nanocrystals including its intrinsic quantum efficiency (IQE). Chemical bath method was employed in the synthesis procedure. X-ray diffraction results showed tetragonal phase for Eu3+ ion concentration in the range 1 and 7 mol% and cubic phase at 8 mol%. The presence of barium oxide (BaO) was confirmed from selected area electron diffraction (SAED). The excitation spectra for these phosphors consisted of broad charge transfer (CT) bands due to the combination of Zr4+ - O2− and Eu3+-O2− charge transfer states. Superimposed on the CT band were direct excitation levels of Eu3+ and Ba2+ ions, in the range 320–450 nm. At high Eu3+ ions concentrations, the intensities of CT bands decreased because some of the ions were coordinated with Ba2+ ions. Photoluminescence emissions for all the doped samples at room temperature appeared to be entirely from intraconfigurational Eu3+ emissions and depended both on the site symmetry as well as the ion concentration. The quadrupole-quadrupole multipolar process was found to be solely responsible for the luminescence quenching. The intensity parameters (Ω2,Ω4), asymmetry ratio, R0 and the average decay lifetime of the nanocrystals showed dependence on concentration. High internal quantum efficiency (IQE) values were obtained at low Eu3+ ion concentrations, but efficiency decreased with increasing ion concentration. The CIE coordinates values were comparable to existing red phosphors and in combination with the high IQE make this phosphor a good candidate for red light emitting applications.

Relation between structure conversion and spectra-tuning properties of Eu2+-doped strontium aluminate phosphor

Phosphors based on strontium aluminates activated by Eu2+ ions with various Al/Sr ratios were synthesized by a traditional high-temperature solid-state method. The influences of Al/Sr ratio, sintering temperature, the doping concentration of europium ions on structural transformation and luminescent properties of the phosphors were studied. The quenching and luminescent mechanisms were also discussed. The optimum synthetic temperature and time are about 1350 °C and 3.5 h derived from the analysis and experiment. At the range of Al/Sr ratio from 1.5 to 4.0, there are only three crystal structures, Sr3Al2O6 (1.5) cubic structure, SrAl2O4 (2.0–3.0) monoclinic crystal system and Sr4Al14O25 (3.0–4.0) orthorhombic crystal system. Under UV light excitation, the emission peaks gradually generate blueshift from 510 nm of Sr3Al2O6:Eu2+ phosphor to 483 nm of Sr4Al14O25:Eu2+ phosphor and the two emission peaks are originated from 4f 65d 1 to 4f 7 intrinsic transition of Eu2+ ions. The best green and blue luminescent samples are SrAl2O4:Eu2+ and Sr4Al14O25:Eu2+, and their color purity is 0.6667 and 0.8229, respectively. The best doping amount of Eu2+ is 0.5 at.%, and the concentration quenching mechanism of Eu2+ ions in SrAl2O4:Eu2+ and Sr4Al14O25:Eu2+ phosphors can be ascribed to the dipole–dipole interaction. There are three types of 6, 7 and 10 coordination numbers around Sr2+(Eu2+) ion, which forms three types of polyhedras, resulting in generating three excitation peaks at 334, 368 and 430 nm corresponding to the 6, 7 and 10 coordination polyhedral. The relation between energy level splitting and coordination number can be expressed as E 6 (6-coordination) > E 7 (7-coordination) > E 10 (10-coordination) in aluminate phosphor, and the splitting width of 6, 7 and 10 coordination numbers is 1.29, 0.78 and 0.31 eV, respectively. The coordination field only affects the energy top of crystal field splitting, and the larger the coordination number is, the lower the energy level top of crystal field splitting in Sr4Al14O25:Eu2+ phosphor is.

Evaluation of europium-doped HA/β-TCP ratio fluorescence in biphasic calcium phosphate nanocomposites controlled by the pH value during the synthesis

Europium-doped hydroxyapatite (HA), beta-tricalcium phosphate (β-TCP) and biphasic phosphate nanopowders were synthesized by co-precipitation method and their crystal structures and fluorescence properties were investigated depending on the pH of the starting solution. In the range of pH 6–10, HA and β-TCP phases coexist. The β-TCP proportion increased as the pH of the solution decreased, while HA yields decreased. At pH below 6, monophasic β-TCP powder was obtained after thermal treatment. In particular, HA and β-TCP can be used as luminescent materials when activated by Eu3+ ions in substitution of Ca2+ ions. Herein, the Eu3+ ions doped HA and β-TCP phase composition were analyzed in order to investigate the fluorescence emission of the HA, β-TCP and biphasic compounds. Eu-doped HA exhibited a red-orange emission at 575nm with several minor peaks at 610–640nm, while Eu-doped β-TCP had an unexpected strong red emission at 610–620nm and a secondary band at 590–600nm. In fact, the Eu:β-TCP integrated emission area is almost 20-fold higher than Eu:HA for the same europium ion concentration. These results demonstrate the potential of Eu:β-TCP as biomarker for medical applications, as drug release and targeting based on their luminescent properties.

Influence of Eu3 + doping content on antioxidant properties of Lu2O3 sol-gel derived nanoparticles

This paper presents the synthesis of pure and europium-doped lutetium oxide (Lu2O3) powders prepared by sol-gel method. The influence of europium ion concentration into Lu2O3 nanocrystallites was investigated for first time in an in vitro system using a modified ABTS radical cation decolorization assay to determine the antioxidant activity. The crystalline structure of Lu2O3 and Eu:Lu2O3 powders was elucidated by XRD obtaining cubic phase in all system without secondary products in accordance with FT-IR results. By TEM and Scherrer equation, it was determined that Lu2O3 and Eu:Lu2O3 powders presented nearly spherical particle morphology with crystallites sizes in the range of 8 to 13nm. The antioxidant assays results revealed that europium ion enhance Lu2O3 powders antioxidant properties, showing that 12.5mol% of europium is sufficient to reach its maximum capacity.

Mechanoluminescence Study of Europium Doped CaZrO3 Phosphor.

Behaviour displayed by mechanoluminescence (ML) in CaZrO3:Eu(3+) doped phosphors with variable concentration of europium ions are described. When the ML is excited impulsively by the impact of a load on the phosphors the ML intensity increases with time, attains a maximum value and then it decreases. In the ML intensity versus time curve, the peak increases and shifts towards shorter time values with increasing impact velocities. Sample was synthesized by combustion synthesis method with variable concentration of Eu(3+) ions (0.1, 0.2, 0.5, 1, 1.5mol%) and characterized by X-ray diffraction technique. The total ML intensity IT is defined as the area below the ML intensity versus time curve. Initially IT increases with impact velocity V0 of the load and then it attains a saturation value for higher values of impact velocities which follow the relation IT=IT (0) exp.(-Vc/V0) where IT (0) and Vc are constants. Total ML intensity increases linearly with the mass of the phosphors for higher impact velocities. The ML intensity Im, corresponding to the peak of ML intensity versus time curve increases linearly with the impact velocities. The time tm, is found to be linearly related to 1000/V0. The mechanoluminescence induced by impulsive excitation in europium doped CaZrO3 phosphors plays a significance role in the understanding of biological sensors and display device application.

Europium Effect on the Electron Transport in Graphene Ribbons

We report in this complementary theoretical–experimental work the effect of gating on the electron transport of graphene ribbons when exposed to very low concentration of europium in an aqueous solution. We find a direct correlation between the level of concentration of europium ions in the solvent and the change in electron transport in graphene, observing a change of up to 3 orders of magnitude at the lowest level of concentration tested (0.1 mM), suggesting a possibility that graphene ribbons can be used for detecting very low concentrations of europium in liquid solutions.

Selective Occupancy of Sites by Rare Earths in K<sub>2</sub>Nd<sub>(1-X)</sub>Eu<sub>x</sub>Nb<sub>5</sub>O<sub>15</sub> Nanopowders, where X = 0, 0.0025, 0.025, 0.05 and 0.1, Prepared by Modified Polyol Method

Niobates with tetragonal tungsten bronze TTB-type structure have presented great technological potential due to their dielectric, ferroelectric, pyroelectric properties. The preparation by the modified polyol method and structural characterization of K2Nd(1-x)EuxNb5O15 nanopowders, where x = 0; 0.0025; 0.025; 0.05 e 0.1, were investigated. The structural parameters were analyzed as a function of concentration of europium ions in the K2NdNb5O15 host structure using the Rietveld method. From structural parameters was determined the TTB-type structure with tetragonal symmetry, where the pentagonal sites is occupied by K+ and Eu3+ ions and tetragonal sites is occupied only by Nd3+ ions. The addition of europium in the host structure led to a decrease in the lattice parameters, compatible with the increasing degree of distortion of NbO6 polyhedra. The average crystallite size showed values between 18.25 and 26nm.

Structural and luminescent properties of Eu3+-doped GdSrAl3O7 nanophosphor

Eu3+-doped GdSrAl3O7 nanophosphor with promising luminescent properties has been synthesized by low-temperature solution combustion synthesis. The structural properties examined by X-ray diffractometer, scanning electron microscopy, and transmission electron microscopy showed that pure tetragonal GdSrAl3O7: Eu3+ red nanophosphor having narrow size distribution in 50–55 nm range could be readily obtained at low temperature 550 °C. The photoluminescent excitation and emission spectra, life time, and concentration effect were studied in detail. Under excitation at 266 nm, Eu3+-doped GdSrAl3O7 nanophosphor revealed weak green emission and strong red emission attributed to 5D1 → 7F1–2 and 5D0 → 7F0–3 transitions of Eu3+ ion, respectively in the region of 525–700 nm. The red emission from 5D0 → 7F2 transition at 616 nm exhibits the highest intensity under the optimized concentration of 10 mol% after which the quenching mechanism became relevant. Quenching behavior of the europium in the GdSrAl3O7 host was explained by nonradiative cross-relaxation phenomenon. Moreover, Eu3+-doped GdSrAl3O7 nanophosphor can generate light from orange to deeper red by properly tuning the concentration of europium ions based on the energy transfer principle.

Combustion Synthesis and Optical Properties of Eu3+-Doped BaGd2ZnO5 f–f Transition Nanophosphor for White LED

An Eu3+-doped BaGd2(1−x)ZnO5 nanophosphor has been synthesized by means of a single-step, urea-assisted, solution-combustion process. The structural, morphological, and optical properties of the nanophosphor were studied by x-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, and photoluminescence spectroscopy. The XRD results showed that the pure orthorhombic BaGd2ZnO5 structure with space group Pbnm was obtained at 900°C. The intense red luminescence at 628 nm on near-UV (396 nm) excitation is because of the hypersensitive 5D0 → 7F2 transition of luminescent activator Eu3+ ions, located at a site with no inversion symmetry in the BaGd2ZnO5 crystal lattice. The optimum doping concentration and decay time of Eu3+-doped BaGd2(1−x)ZnO5 nanophosphor were also determined. The emission could be effectively tuned from blue to the white and red regions by varying the concentration of europium ions. Decay curve analysis revealed that cross-relaxation is primarily responsible for the concentration quenching. High luminescent intensity, low-cost, easy synthesis, uniform shape, and controlled color tunability suggest use of BaGd2ZnO5:Eu3+ as an efficient red-emitting nanophosphor for near-UV-based LED solid-state lighting applications.