Increase Of Eu3 Research Articles

Effect of monovalent, divalent, and trivalent ions codoped with LaOCl: Eu3+ phosphors and its Judd-Ofelt analysis for display device applications

In this work, Lanthanum oxychloride LaOCl: Eu3+ (0–9 mol%) was synthesized using a conventional solid-state approach over the course of relatively low temperature (400 °C) and a shorter duration of 1 h. To investigate the phase purity of phosphors, crystallographic studies were performed using PXRD, which revealed the tetragonal structure with space group P4/nmm (No. 129). Morphological investigations were made using FESEM which unveils the agglomeration of phosphors. Photoluminescence spectra reveals that, the intensity of the 5D0→7F2 transition (618 nm), which increases with an increase in Eu3+ concentration (1–9 mol%), rises to a maximum of 7 mol% before quenching causes it to fall. The reason behind the quenching concentration of Eu3+ ions at 7 mol% was dipole-quadruple interaction which is determined using the Van Uitert equation. To improve luminescence efficiency metal ions like Li+, Na+, K+, Ca2+, and Bi3+ were exploited, among these LaOCl: Eu3+ co-doped with Li+ ion exhibit the highest PL intensity (39 times that of Eu3+). The Commission International de I'Eclairage (CIE) chromaticity coordinates of LaOCl: Eu3+ co-doped with Li+ phosphor is (0.590, 0.346) which is close to commercial red light-emitting phosphors. These phosphor materials were mixed with PVA and developed a flexible phosphor polymer composite, which can be used for flexible display device applications. Spectral parameters like J-O intensity parameters are used to analyze optical materials, these parameters were determined with the help of luminescence spectra.

Luminescence properties of Ca2GdNbO6: Sm3+, Eu3+ red phosphors with high quantum yield and excellent thermal stability for WLEDs

A series of Ca2GdNbO6: xSm3+ (0.01 ≤ x ≤ 0.15) and Ca2GdNbO6: 0.03Sm3+, yEu3+ (0.05 ≤ y ≤ 0.3) phosphors were synthesized by the traditional solid-state sintering process. XRD and the corresponding refinement results indicate that both Sm3+ and Eu3+ ions are doped successfully into the lattice of Ca2GdNbO6. The micro-morphology shows that the elements of Ca2GdNbO6: 0.03Sm3+, 0.2Eu3+ phosphor are evenly distributed in the sample, and the particle size is about 2 μm. The optical properties and fluorescence lifetime of Ca2GdNbO6: 0.03Sm3+, Eu3+ phosphors were detailedly studied. The emission peak at 5D0→7F2 (614 nm) is the strongest and emits red light under 406 nm excitation. The increase of Eu3+ concentration causes the energy transfers from Sm3+ to Eu3+ ions, and the transfer efficiency reaches 28.6%. Ca2GdNbO6: 0.03Sm3+, 0.2Eu3+ phosphor has a quantum yield of about 82.7%, and thermal quenching activation energy is of 0.312 eV. The color coordinate (0.646, 0.352) of Ca2GdNbO6: 0.03Sm3+, 0.2Eu3+ phosphors is located in the red area. The LED device fabricated based on the above phosphor emit bright white light, and CCT = 5400 K, Ra = 92.8. The results present that Ca2GdNbO6: 0.03Sm3+, Eu3+ phosphors potentially find use in the future.

Photoluminescence and optical transition investigations of europium doped bismuth borate glasses for laser and LEDs applications

The current work present the fabrication and characterization of lithium based bismuth borate glasses doped with different europium contents. The grown samples were evaluated for its structural, physical, optical and luminescence investigations. The structural confirmation were conducted by XRD and FTIR spectra. The Absorption spectrum observed in UV-Vis-NIR region and demonstrate two sharp peaks at 2092 and 2200 nm. The bandgap and Judd-Ofelt parameters Ω2, Ω4, Ω6 were computed from absorption spectrum of LiBBiEu2.0 glass. Under 395-nm excitation five emission bands were discovered in the emission spectra. From photoluminescence emission spectra the radiative properties like branching ratio (83), stimulated emission cross section (590.595 × 10−22 cm2), and radiative transition probability (4087.90 s−1), were determined for 5D0→ 7F2 transition. The high optical gain 1.193 × 10−20 cm2 s of LiBBiEu2.0 glass make it possible to be used as best lasing material. From the 5D0 emission level of decay curve the experimental lifetime were calculated which decreased with rise in Eu3+ contents. The increased in orange-red (R/O) ratio with increase in Eu3+ contents confirm asymmetric environment around Eu3+ ions in the host glasses. Based on these results the developed glasses can be used as promising material in red LEDs and red laser in optical devices.

Influence of europium doping on the crystallization, morphology, and the cathodoluminescent properties of PbNb2O6:Eu3+ phosphors

Undoped PbNb2O6 and Eu3+ ion doped PbNb2O6 samples were synthesized by high temperature mixed oxide method, applying a heat treatment temperature of 1250°C and an annealing time of 6 hours. In order to elucidate the structural and optical behavior of PbNb2O6:Eu3+ phosphors, XRD (X-ray diffraction), SEM (scanning electron microscopy), EDS (energy dispersive spectroscopy), CL (cathodoluminescence) and absoption analyses were performed. The X-ray diffraction results showed that the undoped PbNb2O6 sample crystallized in a rhombohedral symmetry while Eu3+ doped samples formed in orthorhombic symmetry. The morphologies of the rhombohedral and orthorhombic grains were examined by SEM-EDS. The CL spectra showed spectral profiles between 580 and 780 nm in relation to the 4f–4f transitions of Eu3+. A strong emission was observed at about 620 nm, corresponding to the red color and associated with the 5D0 → 7F2 transition of Eu3+, while the undoped sample did not exhibit CL emission of the host which is probably due to the presence of lead in the host structure. In addition, the CL analysis results showed that the emission intensity increased with the increase of Eu3+ ion concentration. The increase in magnetic dipole transition caused by the electron beam radiation effect of the CL with increasing doping concentration is associated with the change of dipole moments of the Eu3+ doped tungsten bronze host and thus differentiating the emission spectrum. UV lamp excited photograph of undoped sample showed blue-violet color while Eu3+ doped phosphors with red color became more significant with increasing Eu3+ concentration.

Synthesis, crystal structure, and photo-luminescence properties of a cyan-emitting β-Mg2.25Al3·5Si5·25O18:Eu2+

At the synthesis temperature of α-cordierite (α-Mg2Al4Si5O18), compositions of Mg2+xAl4-2xSi5+xO18 crystallized as β-cordierite (β-Mg2+xAl4-2xSi5+xO18) when x is over 0.2. By doping Eu2+ into optimal host β-Mg2.25Al3·5Si5·25O18 (β-MASO), a series of novel cyan luminescence materials were obtained. Excitation spectra ranged from 250 to 450 nm, and peaked around 365 nm. Under wavelength of excitation peaks, emission maximum of series samples moves from 464 nm to 485 nm with the increase of Eu2+. Decay behaviors and Gaussian multiple fitting results of emission spectrum, consistent with crystal analysis that the Eu2+ occupy three kinds of crystallographic sites. For representative sample β-MASO:0.02Eu2+, internal quantum efficiencies (η1) is about ∼56.96%, and its emission intensity remains at 66% of initial intensity at 150 °C. Under excitation at UV (365 nm) lamp, the white light with warm tune was obtained by mixing β-MASO:0.02Eu2+ with red CaAlSiN3:Eu2+. The electro-luminescence spectrum mainly distributes in blue (400–520 nm) and red (600–740 nm) regions and overlap with main absorption zone of plants.

Synthesis, structure and luminescence properties of bifunctional KCaF3 phosphor influenced by incorporating Eu3+ ions for solid state lighting and TL dosimetry applications

Europium doped KCaF3 phosphors (KCaF3:Eu3+) were prepared using various concentrations of Eu3+ by conventional solid-state reaction process. The X-ray diffraction (XRD) studies confirmed the formation of orthorhombic structured KCaF3:Eu3+ phosphors. Scanning Electron Microscopy (SEM) image of the synthesized phosphor exhibits agglomerated particles with irregular shapes. The composition of the synthesized sample was determined by Energy Dispersive Spectroscopy (EDS) spectrum and elemental mapping showed the homogeneous dispersion of Eu3+ ions into the synthesized KCaF3:Eu3+ phosphor. The emission peak intensity at 594 nm from photoluminescence (PL) spectra was found to increase with the increase of Eu3+ concentrations from 0.02 mol% to 0.06 mol% and decreased with the further increase of Eu3+ concentration up to 0.1 mol%. CIE1931 chromaticity diagram coordinates (x, y) of KCaF3:(0.06 mol%) Eu3+ phosphors were positioned in the reddish-orange region (x = 0.5736, y = 0.4224). Photoluminescence property confirms the suitability of KCaF3:Eu3+ phosphors for Solid state lighting application. X-ray induced luminescence (radioluminescence, RL) is recorded for KCaF3:Eu3+ phosphors showing the characteristic emission of Eu2+ and Eu3+. ESR study on KCaF3:Eu3+ phosphors confirm the presence of Eu2+ ions. Beta irradiated thermoluminescence (TL) glow curve of Eu3+ doped KCaF3 phosphors is measured and deconvoluted using Gaussian fitting. TL kinetic parameters like activation energy (Ea) and frequency factor (s) are calculated for all the deconvoluted peaks using peak shape method which shows the synthesized KCaF3:Eu3+ phosphors is suitable for dosimetry application.

Cation Valences and Multiferroic Properties of EuTiO3 Co-Doped with Ba and Transition Metals of Co/Ni.

Eu1−xBaxTi1−yMyO3 (M = Co or Ni) was sintered at 1400 °C under a reduction atmosphere. X-ray photoelectron spectroscopy revealed the mixed valences of Eu2+/Eu3+ and Ti4+/Ti3+ in EuTiO3 and Eu0.7Ba0.3TiO3, as well as some oxygen vacancies required to keep the charge neutrality. The co-doping of Co2+/Ni2+ in Eu0.7Ba0.3TiO3 resulted in the disappearance of oxygen vacancies, as a result of a reduction in Ti3+ numbers and an increase in Eu3+ numbers. On the other hand, Ba2+ doping led to an increased lattice parameter due to its larger ionic size than Eu2+, whereas the Co2+/Ni2+ co-doping resulted in smaller lattice parameters because of the combined effects of ionic size and variation in the oxygen-vacancy numbers. Eu0.7Ba0.3TiO3 exhibited a clear ferroelectricity, which persisted in the Co2+/Ni2+ co-doped samples until the doping levels of y = 0.05 and 0.10, respectively. Eu0.7Ba0.3TiO3 remained to be antiferromagnetic with a reduced transition temperature of 3.1 K, but co-doping of Co2+/Ni2+ turned the samples from antiferromagnetic to ferromagnetic with transition temperatures of 2.98 K and 2.72 K, respectively. The cause for such a transition could not be explained by the larger lattice volume, oxygen vacancies and mixed valences of Eu2+/Eu3+, which were proposed in previous works. Instead, it was more likely to arise from a large asymmetric distortion of the Eu–O polyhedron introduced by the aliovalent doping, which promotes the admixture of Eu 5d and 4f states.

X‐Ray Luminescence, Photoluminescence, and Radiation Shielding Properties of Europium‐Doped Oxide Glasses for Red Light‐Emitting Device Applications

This study is focused on bringing significance to the X‐ray luminescence, photoluminescence, and radiation shielding properties of Eu3+ ions doped oxide glasses. X‐ray luminescence spectra show signature emission peaks at 579, 590, 613, 645, and 700 nm corresponding from 5D0 to 7F0, 1,2,3,4. The asymmetry ratio decreases with an increase in Eu3+ concentration. X‐ray luminescence shows the highest and broad emission at 613 nm followed by 700 nm. Judd–Ofelt (J–O) analyses are employed to understand the oscillator strength and to obtain radiative properties. Thermal corrections are instigated using the J–O theory. The phonon sideband analysis is studied and it is found that the prepared glasses show phonon energy around 1384 cm−1. Radiative properties are employed using J–O parameters. The quantum efficiency for 1 mol% Eu2O3 content is 60.57%. Structural analysis is employed using a Fourier transform infra‐red study and it is found that the glasses show signature B–O vibrations in BO3 and BO4 units. The CIE 2015 color coordinate, delta UV, and color correlated temperature values are evaluated. Radiation shielding properties such as mass attenuation coefficient, total attenuation coefficient, effective atomic number, and electron density are calculated. Higher radiation shielding values are observed for the Eu2O3 doped glasses compared to undoped glasses.

Tunable color and energy transfer of Y2Mg3Ge3O12: Tb3+, Tm3+, Eu3+ phosphors with excellent thermal stability

Y2Mg3Ge3O12: RE3+ (RE ​= ​Tb, Eu, Tm) phosphors were prepared by solid phase method. XRD and EDS show that the samples were pure phases. The ET efficiency of Y2Mg3Ge3O12: Tb3+, Eu3+ can reach up to 96.63%, and the mechanism is d-d interaction. In Y2Mg3Ge3O12: Tb3+, Eu3+, Tm3+, the intensity of Tb3+ decreases with the increase of Eu3+ concentrations, and the intensity of Tm3+ is basically unchanged, the intensity of Eu3+ increased first and then decreased. Meanwhile, the ET efficiency can reach up to 77.53%. Moreover, the luminescence intensity at 423 ​K can still be maintained at 87–96.58% of that at the initial temperature. The value of CCT which shows a decreasing trend with increasing Eu3+ concentrations also indicates that warm white light can be obtained by triple doping of Tb3+-Eu3+-Tm3+. The above findings show that these samples are likely to be used in warm w-LEDs.

Influence of Eu3+ substitution on structural, magnetic and dielectric properties of Bi0.9La0.1FeO3

Enhanced magneto-electrical (ME) properties of BiFeO3 multiferroics are attained by the modification of structural morphology that is essential for the possible applications in multifunctional devices like miniaturization. This study focused on the improvement of the magnetic and dielectric properties in an ideal BiFeO3 achieved by the gradually substitution of Eu3+in place of Fe3+ (B-site) with slight addition of La3+ replacing Bi3+ (A-Site). In this regards the composition Bi0.9La0.1Fe1-xEuxO3 (x = 0, 0.02, 0.05, 0.07, 0.10 and 0.15) were synthesized by solid state reaction method. XRD patterns indicate the samples crystallize with the normal distorted rhombohedral phase (R3c space group) and oxygen vacancies are significantly suppressed by the increase of Eu3+ amount. The lowest porosity (1.9%) is observed in the sample for x = 0.07. The crystallite sizes are increased due to 15% Eu doping. The average size of the grains are observed to be increased in the micrograph for Eu doping compared to the undoped one. The strongest absorbance peak around 560 cm−1 in FTIR spectroscopy for all the samples confirm the octahedral FeO6 bonding while a pair of feeble peaks around 370 cm−1 and 440 cm−1 confirm the existence of BiO6 octahedral phase adjacent with FeO6 group. The magnetic saturation (Ms) is 0.89 emu/g for the undoped Bi0.9La0.1FeO3 and Ms increases for Eu3+ substitution at the Fe-site of the compound. The maximum Ms (1.58 emu/g) is observed in the sample for x = 0.07. The permeability (μ) and permittivity (ε) are highly affected by the reformed structure with various grain sizes and porosities (%) which have been reported in this work. The composition for 7% Eu3+ doping shows an excellent matching between μ’ and ε’ (μ’/ε’=0.9) with lower magnetic loss (tanδμ = 0.0133) over the frequency range from 1 MHz to 100 MHz.

Thermally enhanced photoluminescence and temperature sensing properties of Sc2W3O12:Eu3+ phosphors

Recently, lanthanide-ion-doped luminescent materials have been extensively used as optical thermometry probes due to their fast responses, non-contact, and high sensitivity properties. Based on different responses of two emissions to temperature, the fluorescence intensity ratio (FIR) technique can be used to estimate the sensitivities for assessing the optical thermometry performances. In this study, we introduce different doping concentrations of Eu3+ ions into negative thermal expansion material Sc2W3O12 to increase the thermal-enhanced luminescence from 373 K to 548 K, and investigate the temperature sensing properties in detail. All samples can exhibit their good luminescence behaviors thermally enhanced. The emission intensity of Sc2W3O12:6-mol% Eu3+ phosphor reaches 147.8% of initial intensity at 473 K. As the Eu3+ doping concentration increases, the resistance of the sample to thermal quenching decreases. The FIR technique based on each of the transitions 5D→ 7F1 (592 nm) and 5D→ 7F2 (613 nm) of Eu3+ ions demonstrates a maximum relative temperature sensitivity of 3.063% K−1 at 298 K for Sc2W3O12:6-mol% Eu3+ phosphor. The sensitivity of sample decreases with the increase of Eu3+ concentration. Benefiting from the thermal-enhanced luminescence performance and good temperature sensing properties, the Sc2W3O12:Eu3+ phosphors can be used as optical thermometers.

A dual-emission fluorescent ratiometric probe based on bimetallic lanthanide complex interacted in nanoclay for monitoring of food spoilage

Owing to increasing food-safety issues, food insecurity is an enormous threat to human health and the economy. Therefore, it is necessary to explore efficient and early food spoilage detection. Herein, we develop a ratiometric fluorescent probe based on the embedding of bimetallic Ln3+ (Eu3+ and Tb3+) complex intercalated in nanoclay, which can monitor the real-time visual surveillance freshness of food. The fluorescent probe exhibits a dual-emission responsive to biogenic amine along with a significant decrease in Tb3+ emission intensity and an increase in Eu3+ emission intensity, enabling an obviously distinguishable color transition from yellow to orange to rose red clearly discerned by naked eyes. The probe shows an outstanding response and excellent sensitivity which has a low limit of detection (LOD=0.137 mg L−1) for target biogenic amines (histamine) in the range (4–22 mg L−1). Besides, we use the gel to inspect the change in the freshness of raw fish in a hermetic space. It is proved that the nanocomposite can be applied to the on-site inspection of the food freshness. This work provides a novel direction for the evolution of fluorescent nano-clay based lanthanide complexes as a new platform for application in food surveillance.

A potential red-emitting phosphor Na2.5Zr2Si1.5P1.5O12: Eu3+ for WLEDs with excellent thermal stability, color purity and high quantum efficiency

Developing and researching high quantum efficiency red phosphor with small thermal quenching performance was vital for white light-emitting diodes (WLEDs). Herein, a series of novel red emitters Na2.5Zr2-xSi1.5P1.5O12: xEu3+ (NZSPO: Eu3+, 0 ≤ x ≤ 0.07) were prepared and studied. The detailed crystal structure, morphology features and coordinated information of the cations were studied by X-ray diffraction, Rietveld refinement and SEM. The spectral analysis results showed that NZSPO: Eu3+ phosphor could exhibit excellent CIE chromaticity coordinate and high color purity. Excitingly, the internal quantum efficiency of the optimized NZSPO: 0.05Eu3+ could reach 72.14%. And the intensity could still keep 93.3% compared with the initial emission intensity at 140 °C. The concentration quenching mechanism was investigated and then demonstrated to be dominated by the dipole-dipole interaction. In addition, the lifetime of NZSPO: Eu3+ decreased with the increase of Eu3+ concentration, and the average decay time was 1.85 ms. The CCT of the white light emitted by the packaged WLED was 5337 K and the CIE coordinates could reach (0.3357, 0.3338), which was on the verge of the standard white coordinates (0.33, 0.33). All the results showed that NZSPO: Eu3+ could be served as a prospective red light-emitting phosphor for WLEDs.

Synthesis optimisation and efficiency enhancement in Eu3+ doped barium molybdenum titanate phosphors for w-LED applications

Barium Molybdenum Titanate (Ba3MoTiO8) phosphor activated with Eu3+ ions has been synthesized successfully by three different routes such as solid-state reaction method (SSM), combustion method (CMM), and sol-gel combustion method (SGM) to optimize relatively best synthesis technique and temperature of synthesis. X-Ray Diffraction (XRD) patterns have been used to confirm the phase and crystallinity of the as-prepared phosphor. Scanning Electron Microscope (SEM) and Raman spectra have been used to study the morphological behaviorhas and different vibrational bands present in the structure of the titled phosphor respectively. Diffuse Reflectance Spectra (DRS) have been recorded to find out the optical band gap of phosphors. Photoluminescence (PL) spectral features recorded under 393 nm and 465 nm excitation wavelengths reveal an intense red emission at 612 nm corresponding to 5D0→7F2 transition of the doped Eu3+ ions. CMM synthesized sample has shown maximum luminescence intensity out of the three methods and further studies have been carried out by preparing a series of europium ions doped Ba3MoTiO8 phosphor using the CMM technique. The PL decay curves recorded for 612 nm red emission under 393 nm excitation show non-linear double exponential nature with a decrease in an experimental lifetime with an increase in Eu3+ ions concentration in the as-prepared phosphors. All the morphological and photoluminescence studies carried out on the Eu3+ ions doped Ba3MoTiO8 phosphor contemplate the suitability of the as-prepared phosphor for a red component in white light-emitting diode (w-LEDs) applications.

Effective sensitization of Eu3+ visible red emission by Sm3+ in thermally stable potassium zinc alumino borosilicate glasses for photonic device applications

Sm3+/Eu3+ co-doped thermally stable potassium zinc alumino borosilicate glasses prepared by melt quenching method have been characterized by using spectroscopic techniques to understand their luminescence behavior. For an undoped glass, the XRD pattern recorded confirms the amorphous nature whereas FT-IR and Raman spectrum confirms the functional groups present. Addition of Sm3+ ions as a sensitizer makes the as prepared glasses more efficient for display devices. The mechanism of the energy transfer from Sm3+ to Eu3+ ion has been observed through non-radiative process. The non-exponential time decay curves are giving decreasing lifetimes with increase in Eu3+ ion concentration confirms the energy transfer. The calculated CIE points for the glasses move towards the red region with increase in the concentration of Eu3+ ions under the UV excitation. All the results obtained contemplate the suitability of the as prepared glasses for photonic device applications such as w-LEDs, solar cells and display devices.

A novel Eu2+/Tb3+ co‐doped phosphor with pyroxene structure applied for cryogenic thermometric sensing

AbstractPyroxene‐type phosphors were widely developed due to the advantages of high chemical stability, luminous efficiency, and low production cost. In this contribution, a series of Eu2+/Tb3+ co‐doped Ca0.75Sr0.2Mg1.05Si2O6 (CSMS) phosphors with pyroxene structure were successfully synthesized by the solid‐state method. Under the 340 nm excitation, the emission peaks of the phosphor show a redshift with the increase of Eu2+ concentration. The emitting color of Eu2+/Tb3+ co‐doped samples shows a redshift attributed to the energy transfer from Eu2+ to Tb3+. Simultaneously, acquired thermometer exposes superbly temperature‐sensitive properties (Sa and Sr having maximum values 4.7% K−1 and 0.6% K−1, respectively) over the cryogenic temperature range (77–280 K). Furthermore, it has good stability and precision at cryogenic temperatures, indicating that CSMS:0.03Eu2+/0.03Tb3+ phosphor is a very promising fluorescent material suitable for cryogenic temperature sensing.

Luminescence and energy transfer of Dy3+-Eu3+ co-doped glass-ceramics containing ZnMoO4

Dy3+-Eu3+ co-doped glass-ceramics (GCs) containing ZnMoO4 were successfully prepared. The temperature range of heat treatment was preliminarily determined by differential scanning calorimeter (DSC) and thermogravimetry (TG). The crystalline phase was determined by X-ray diffraction (XRD), the structural feature was analyzed on the basis of Rietveld refinement, the morphology was observed by scanning electron microscopy (SEM), the absorption coefficients were calculated by light transmission curves. Combined with the above analysis, the optimal heat treatment condition was discussed. Through the fluorescence spectra and decay curve, there existed an energy transfer between Dy3+ and Eu3+, and the energy transfer efficiency from Dy3+ to Eu3+ increased with the increase of Eu3+ concentration. By calculating the critical distance and linearly fitting the data, it could be concluded that the mechanism of energy transfer was dipole-dipole interaction. With the changed of Dy3+-Eu3+ doped concentration, the color coordinates of these samples can be tuned in the white light region, and the 0.4% Dy3+-0.7% Eu3+ co-doped glass-ceramics obtained warm white light emission with low correlated color temperature (CCT). These results clearly showed that Dy3+-Eu3+ co-doped GCs containing ZnMoO4 could be used as a potential candidate material in the field of white light-emitting diodes (w-LEDs).

Polymorph controlled synthesis and photoluminescence properties of Eu3+ doped BiNbO4

Homogeneous doping of rare earth (RE) ions at atomic level is ideal for enhancing luminescence efficiency. Molten-salt synthesis facilitates crystal growth with improved phase-selectivity and dopant homogeneity. Herein, we present a facile and phase-selective synthesis of orthorhombic α-BiNbO4 and monoclinic β-BiNbO4 under Na2SO4-K2SO4 fluxes in the temperature range of 900 °C to 1050 °C. A series of Eu3+ doped BiNbO4 samples with different crystalline structures were obtained. The influences of Eu3+ doping on the crystal structure were systematicly investigated. α-BiNbO4 has a higher Eu3+-doping limit (>15 mol%) while β-BiNbO4 was unstable upon Eu3+ doping and gradually transformed into α-BiNbO4 with the increase of Eu3+ doping concentration. Moreover, all prepared Eu3+ doped BiNbO4 samples can be effectively excited by near-ultraviolet and blue light and exhibit intense red emissions due to the 5D0/7F2 transition of Eu3+ ions. In addition, the quenching concentration can reach above 10 mol% Eu3+ for both polymorphs. The temperature-dependent emission results revealed that α-BiNbO4 possesses a superior thermal stability with activation energy of 0.271 eV, larger than β-BiNbO4 with activation energy of 0.233 eV. The results reported here provide new insights into the understanding of polymorph-dependent property for photon down-conversion rare-earth luminescence of BiNbO4:Eu3+.

Novel red-emitting phosphor La2Ti6O15:Eu3+ for fabricating warm white LED-devices

Eu3+-doped La2Ti6O15 nanoparticles were prepared by the sol-gel process. The phase-formations, crystal structure, photoluminescence properties, and lighting application were reported. La2Ti6O15 has band energy of 3.6 eV, which can be narrowed with the increase of Eu3+-doping in the lattices. A broad intrinsic emission band (400–750 nm) peaked at 515 nm was observed at 300 K Eu3+-doped La2Ti6O15 phosphors present bright red-luminescence from 5D0→7F2 transitions (615 nm). The luminescence has an excellent thermal stability performance with an activation energy of ΔE = 0.33 eV. Importantly, it fits well with the commercial LED-chip because of its efficient excitation in blue (465 nm) and near-UV region (395 nm). Red-LED device packaged with the optimal phosphor was achieved with luminous efficiency of 43.75 lm/W. It was suggested that La2Ti6O15:Eu3+ could be a potential candidate for fabricating high-power warm white-LEDs.

Impact of Ag species on luminescence and spectroscopic properties of Eu3+ doped fluoro-phosphate glasses

In this paper, we investigate the influence of silver (Ag) doping concentration on structural, luminescence and spectroscopic features of Eu3+ doped fluoro-phosphate glasses. Highly transparent glasses were prepared using the classic melt-quenching route. The vitreous structure of the glasses has been confirmed by XRD analysis. Absorption and luminescence studies indicate the presence of different Ag species in the glassy host. Our results suggest that the greatest enhancement of Eu3+ luminescence can be ensured by an energy transfer (ET) from single Ag+ ions and molecular-like (ML)-Ag nanoclusters (NCs), as evidenced by a maximum increase in Eu3+ luminescence intensity upon excitation of 442 nm, which is the direct excitation of these species. Judd-Ofelt model was used to investigate the local structure around the active Eu3+ ions and evaluate their radiative parameters under Ag doping. Such parameters suggest that the present glass is promising as efficient and stable luminophore.