Transition Of Eu Research Articles

Concentration effect on the luminescent and structural properties of YPO4: Eu3+

Different concentrations of Eu3+ doped YPO4 samples were prepared using the co-precipitation reaction. The prepared samples were characterized by using XRD, PL (Photoluminescence), and FTIR. The crystallite sizes of the samples are found to be in the range of 10–18 nm. Photoluminescence studies give information about the excitation and emission spectra of the synthesized samples. Among the different concentrations of Eu3+ doped samples, 5at.% doped sample gives the highest emission spectrum as compared to others. Two intense emission peaks were found at 593 nm and 618 nm. These peaks are due to 5D0 -7F1 (magnetic dipole transition) and 5D0 - 7F2 (electric dipole transition) transitions of Eu3+ respectively. The average lifetime of the synthesized samples is found to be 3.52 ms.

Synthesis and PL Characterization of Zn4B6O13 : Eu3+ Phosphor

Modified solid state synthesis had been used to synthesize Zn4B6O13:Eu3+ phosphor. Compared to other methods, modified solid-state synthesis has several advantages.. Zn4B6O13:Eu3+ phosphor’s’ photoluminescence properties have been investigated.. The PL excitation spectra shows sharp peak at 393nm due to transition of 4f→5d. The shoulder peak of the PL emission spectra is observed at 614nm due to the 5Do→ 7F2 (red) transition of Eu3+ ion while the other peak is observed at 593nm due to the 5Do→ 7F1 (orange). All of the properties of the developed Zn4B6O13:Eu3+phosphor indicate that it could be beneficial in the lamp industry and solid state lighting.

Achieving Bright Reddish-Orange Luminescence in CaSnO3 Ceramics through Doping Manipulation

The reddish-orange phosphors of rare-earth activator have attracted intense interest due to their applications in lighting and display devices, including plasma display panel, field emission display and white light diode. In this work, Eu-doped CaSnO3 phosphor materials were prepared and examined. Their X-ray diffraction patterns were used for lattice parameters calculations and show that there was no phase transformation in all doping conditions. XANES studies suggest the stabilization of Sn and Eu ions in 4+ and 3+ oxidation states in the prepared phosphors, respectively. A broad emission band, with a major peak at 614 nm upon excitation wavelength of 395 nm, was observed in the range of 550 to 730 nm at room temperature due to 5D0 → 7FJ transition of Eu3+ ions. The luminescent spectra of the samples showed the intense light emission in the red-orange light region.

A novel blue emitting europium doped lanthanum magnesium hexaaluminate long persistent phosphor and analysis of traps distribution

Long persistent luminescent (LPL) materials are highly anti attention due to its energy conservation and environmental protection. Here, a novel blue LPL material LaMgAl11O19: Eu2+ (LMAO: Eu2+) have been synthesized successfully by high temperature solid state method, and its LPL properties was studied for the first time. The X-ray diffraction, refinement and crystal structure were used to characterize the phase composition of the synthesized samples. The LMAO: Eu2+ phosphor mainly exhibits blue center at 454 nm, which was mainly attributed to the 5 d-4f transition of Eu2+. The LPL properties were characterized by the LPL decay curves, LPL spectrum and the thermoluminescence (TL) curves. After removing the excitation sourc e, a blue LPL is produced approximately 9 min. Finally, the trap distribution and LPL mechanism are analyzed in detail through TL spectroscopy.

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+.

Eu3+ and Tb3+ doped LiCaY5(BO3)6: Efficient red and green phosphors under UV or NUV excitations

Eu3+ and Tb3+ are typical red and green-emitting photoluminescent (PL) activators and rare earth borates are well-known good PL hosts. In this contribution, a recently reported borate LiCaY5(BO3)6 was selected as the host to study the Eu3+ and Tb3+ photoluminescence systematically. LiCa(Y1-xEux)5(BO3)6 (0 ≤ x ≤ 1), LiCa(Y1-yTby)5(BO3)6 (0 ≤ y ≤ 1) and LiCa(Y0.88-zTb0.12Euz)5(BO3)6 (0.01 ≤ z ≤ 0.07) were synthesized by solid state reactions and the powder X-ray diffraction proved the high purity and crystallinity by quantifying the unit cell volume expansion when replacing Y3+ with Eu3+ and Tb3+. Charge transfer band and f-f transitions of Eu3+ in ultraviolet (UV) and near UV range are both intense because there exists a strongly noncentrosymmetric site in the host. Concentration quenching effect was also observed at x = 0.30 and 0.50 when excited by CTB and 392 nm, respectively. For Tb3+, strong f-d and weak f-f transitions were observed along with the typical green emission, and the concentration quenching occurs at y = 0.12 and 0.30, respectively. It is interesting to observe the Tb3+ to Eu3+ energy transfer in co-doped phosphors, thus the color tunable emissions from green to yellow, and to red were realized by manipulating the dopant concentrations. A preliminary trial to combine these borates with NUV LED chips gave typical red, green, and warm white lights, indicating the potentials as LED-pumped phosphors.

Effect of pH on synthesis, characterization and fluorescence behavior of WO3:Eu3 nano powders

WO3:Eu3+ nanoparticles with different pH values were prepared by citric acid method. The structure and morphology of nano-powders were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The luminescence properties of the nano-powders were tested by a fluorescence spectrometer. The results showed that the average particle size of the prepared WO3:Eu3+ nano powders were the smallest and reached 32 nm at pH = 1. Under different excitation wavelengths, the main emission peak of the sample was at 615 nm, corresponding to the 5D0 →7F2 electron transition of Eu3+. The emission intensity of WO3:Eu3+ nanoparticles prepared at pH = 5 was the highest at 615 nm.

Investigation on photoluminescence and Judd–Ofelt parameters in Eu ion-doped CaZrO3 in relation to the local structural property

In this study, we investigated the photoluminescence (PL) of Eu ion-doped CaZrO3 in a wide doping concentration range (x = 0.005–0.1). The change in the local structure with Eu3+ doping was analyzed by employing Rietveld refinement on the X-ray diffraction patterns. X-ray photoemission spectroscopy revealed that the valence states of Eu ions are mainly trivalent in the CaZrO3 matrix for all doping concentrations. The emission spectra of our samples showed series peaks originating from the f-f transitions of Eu3+ ions in the red–orange region under ultraviolet photoexcitation. The time-resolved PL measurement demonstrated that the rising time decreased at higher x and that the average decay times were not affected by the doping concentration. The Judd–Ofelt parameters calculated from the PL spectra indicated that the asymmetry ratios changed non-monotonically with the increasing doping concentration of Eu3+, which is in good agreement with the local lattice properties of our samples.

Fluorescence and crystal structure of SrLa1-x AlO4 :xEu3+ phosphor synthesized using a sol-gel method.

The SrLa1-x AlO4 :xEu3+ phosphors were obtained using one calcination of a precursor synthesized using a sol-gel method. When excited at 396 nm, this phosphor emits a red light mixed with several strong peaks centred at 596 nm, 616 nm and 625 nm, attributed to 5 D0 →7 F1, 2 transitions of Eu3+ ions, respectively. The concentration quenching occurs at x = 1.5 mol%mol of SrLa1-x Eux AlO4 and the critical energy transfer distance is calculated to be 13.13 Å, the dipole-dipole interaction was found to play a role. In addition, the colour purity could be up to 97.5%. Simultaneously, the thermal stability of SrLaAlO4 :Eu3+ was measured and the thermal quenching was found at c. 275°C (T0.5 ), the excitation energy was 0.19 eV. Current results demonstrate that SrLaAlO4 :Eu3+ could be a red component candidate for white light LEDs pumped by near-UV chips.

Energy transfer mechanism of KAlF4:Dy3+, Eu3+ co-activated down-conversion phosphor as spectral converters: An approach towards improving photovoltaic efficiency by downshifting layer

Rare earth activated fluoride phosphors have attention in recent years in the field of solid state lighting and solar cell efficiency enhancement. In the present study, RE (RE = Dy3+, Eu3+) activated/co-activated KAlF4 phosphor has been synthesized by low temperature wet chemical method. The structural feature of the samples was analyzed by X-ray Diffraction (XRD), which showed that the samples were crystallized in a well known structure. Photoluminescence (PL) measurement of KAlF4:Dy3+ phosphors we find that they can be efficiently excited at 351 nm and possess dominant emission bands centered at 482 nm (blue) and 572 nm (yellow). From Photoluminescence (PL) measurement of KAlF4:Eu3+ phosphors a strong orange emission at the peak wavelength of 594 nm and 616 nm were observed which could be attributed to the 5D0 → 7F1 and 5D0 → 7F2 transition in Eu3+ ions. On co-doping of rare earths in the host lattice, a strong blue and yellow emissions were observed together with the red emission. This co-doped phosphor is the coated on Si-solar cell by doctor blade method. Solar cell efficiency has been checked by I-V characteristics of the coated and blank cell. Theoretical quantum efficiency has been determined by Judd–Ofelt parameters for the proposed phosphor.

Morphological and optical studies of Gd2O3:Eu nanostructures synthesized via sacrificial template directed co-precipitation route

The morphology of the phosphors plays a major role in altering luminescent characteristics, which can be altered using different templates. The present paper reports for the first time template directed co-precipitation synthesis of Gd2O3:Eu phosphors. Three water soluble templates i.e., Thioglycerol (TG), Dextran, and Polyvinylpyrrolidone (PVP) in varying amount of 0.5 to 2.5 wt% were used during synthesis. The effect of templates on the structural, morphological and luminescent properties of Gd2O3:4mol%Eu phosphors were investigated. The addition of the templates during synthesis altered the morphology of the samples significantly. All the samples exhibited sharp, narrow and intense emission spectra, corresponding to the 5D0-7F0,1,2,3,4 transitions of Eu3+ ions. The photometric parameters such as CIE coordinates and CCT values were determined to check their applicability for practical applications. The synthesized phosphors find potential applications in optoelectronic devices and bio-medical applications.

Eu3+-doped Bi2MoO6 phosphors for highly sensitive and visible H2S gas indicator material: optical and color properties, and gas sensing performance.

Bi2MoO6:Eu3+ phosphors were synthesized by a solid state reaction, and H2S gas sensing performance was investigated. The Bi2MoO6:Eu3+ phosphors showed an excellent red emission due to f-f transition of Eu3+. Owing to the exposure to H2S gas, the emission intensity of the phosphors dramatically decreased to 40% of the initial value. The body color of the phosphor changed from yellow-white to dark brown. The response of the Bi2MoO6:Eu3+ phosphors for H2S gas was started from 10 ppm, and the emission intensity exponentially decreased with increasing the concentration until 500 ppm.

Structural and optical properties of Eu3+ ions in lead glass for photonic applications

The new glass system, with the chemical composition xEu2O3•(100 − x)[4PbO2•Pb] where x = 0-10 mol% Eu2O3, obtained by melt quenching method, was investigated by XRD analysis, FTIR, UV-Vis and PL spectroscopy for optical devices applications. The XRD analysis reveals the vitreous structure of the obtained samples. The FTIR absorption spectra reveal the evolution of the [PbO3], [PbO4], and [PbO6] basic structural units in the glass network as a function of the rare earth content. The disintegration of the [PbO6], octahedral structural units into Pb2+ and non-bonding oxygen ion centers was exhibited in UV–Vis spectra. The optical parameters confirmed the formation of non-bridging oxygen ions and defects in the glass network. Under 395 nm excitation wavelengths, the PL spectra showed the simultaneous emission of the Pb2+ and f−f transitions of Eu3+ ions. The Color parameters manifest that the europium doped lead-based glasses are suitable for w-LED.

Morphology control and luminescent properties of Eu/Tb-doped calcium carbonate nanoparticles using natural limestone

The Eu/Tb-doped CaCO3 nanocrystals including nanoneedles, nanorods and nanospheres are respectively synthesized from natural limestone via carbonation technique. The doping of Eu/Tb ions can not change the polymorph, but the morphologies and sizes of synthesized CaCO3 differ significantly depending on the species and concentrations of Eu/Tb ions. The undoped CaCO3 nanoneedles exhibit a length of 280–920 nm and a diameter of 55–78 nm, while the 6% Eu doped CaCO3 nanorods exhibit a length of 1.68–2.56 μm and a diameter of 560–680 nm, respectively. The introduction of Tb ions changes the CaCO3 morphology from nanoneedle to irregular sphere and the diameter of CaCO3: 8% Tb primary particle is around 110–200 nm. Under the excitation of 318 nm or 384 nm ultraviolet light, CaCO3: x% Eu nanorods exhibit characteristic emission bands at 360 nm and 420 nm assigned to 4f6 5 d1(t2g) →8S7/2 transition of Eu2+ ions and sharp peaks at 596 nm from the 5D0 →7F1 transitions of Eu3+ ions. XPS data further confirm the coexistence of Eu2+ and Eu3+ ions. The CaCO3: y% Tb nanospheres present intense blue-green emission at 424 nm and 545 nm under excitation at 397 nm, which are originating from both 5D3→7FJ and 5D4→7FJ transitions of Tb3+ ions. However, under 343 nm excitation, in addition to the emission of Tb3+, Eu3+ ions also present intense emissions at 572 nm, 596 nm, 624 nm and 650 nm, which may be caused by the unknown Eu -containing impurities from natural limestone. Whiteemitting and color-tunable photoluminescence performance of CaCO3 nanostructures are realized by regulating the excitation wavelengths and doping ions.

Structural, surface and luminescent properties of SrF2:Eu annealed thin films

The effect of calcined temperature on the structural, surface and luminescent properties of a SrF2:Eu thin film were investigated for possible application as a downshifting layer for solar cell application. The film was deposited on sodium lime glass by a spin coating method and obtained after heat-treatment under Ar/H2 atmosphere. The thin film's structure as well as the morphology were investigated with X-ray diffraction and scanning electron microscopy, respectively. The elemental composition of the film was obtained with X-ray photoelectron spectroscopy (XPS). The XPS depth profile showed that oxygen and silicon segregated into the 600 °C calcined film and formed an intermediate layer. The XPS results for the SrF2 thin films confirmed that the elements of thin film existed in their stable form on the surface. The electric dipole allowed transitions of Eu2+ ions dominated the film's photoluminescent (PL) spectra at low calcination temperatures. The 5D0-7F0 PL transition of Eu3+ was, however, observed at elevated temperatures. The results suggested that Eu might be a good sensitizer for other lanthanide ions, such as Tb3+ and Er3+, at low temperature treatments.

Full-color emitting crystal engineered Sr3Al1−xSixO4+xF1−x: Eu2+/3+ oxyfluorides for developing bendable lighting composites

A series of full-color emitting Eu2+/Eu3+-coexisted Sr2.9Al1−xSixO4+xF1−x: 0.1Eu2+/3+ (SASixOF: Eu2+/3+) oxyfluorides were synthesized by annealing the solid precursors in oxygen-deficient atmosphere. The structural changes in Sr3AlO4F (SAOF) owing to the Si4+ ions’ doping were visualized from the Rietveld refinement analysis. The substitution of Si4+ ions in Al sites contracted the AlO4 tetrahedra and could enlarge the Sr sites, and enabled the suitable occupation of Eu2+ ions in the Sr1 sites. Eventually, the X-ray photoelectron spectroscopy studies confirmed the valence conversion of europium ions from its trivalent to the divalent state owing to the Si4+ ions doping in SAOF: Eu2+/3+. Photoluminescence studies of SASixOF: Eu2+/3+ showed a bluish emission band at 482 nm for the 4f-5d transition of Eu2+ ions along with several sharp peaks above 550 nm owing to the intra f-f transition of Eu3+ ions. Increasing the Si4+ ions’ concentration subsequently, enhanced the Eu3+ to Eu2+ conversion rate decreased their emission intensity ratio, owing to which the emission color chromaticity was also tuned from orange-red (CIE: 0.48, 0.29) to nearly white (CIE: 0.30, 0.26) and eventually to the bluish region (CIE: 0.18, 0.23). The nearly white light-emitting composition SASi0.03OF: Eu2+/3+ and the intense bluish light-emitting optimum SASi0.06OF: Eu2+/3+ phosphors were further chosen for fabricating flexible composites based on phosphor and castor oil (CO). At 150 °C, the composite showed almost double emission than the phosphor powders owing to the thermal encapsulation of the powders provided by the CO matrix. The obtained composite started to degrade at a temperature as high as 300 °C. Therefore, the composite made with near white emitting SASi0.03OF: Eu2+/3+ phosphor was integrated with a 372 near UV-LED which showed intense cool white emission with the CIE of (0.29, 0.33), CCT of 7562 K, and CRI of 89. The above studies broadly suggested the adaptability of the obtained composites for flexible lighting applications.

Synthesis and photoluminescence properties of novel red-emitting KMg4(PO4)3: Eu3+ phosphors for UV-excited white-light emitting diodes

The trivalent Eu3+ activated KMg4(PO4)3 phosphor has been successfully prepared via solid state diffusion technique. The phase formation and structural morphological studies carried out by XRD pattern and SEM analysis. The photoluminescence excitation spectra centred at 395 nm attributed to 7F0→5L6 energy transition levels. PL emission spectra centred at 593 nm and 613 nm corresponds to 5D0→7FJ( J=1,2) transitions of Eu3+ in the host respectively. The experimental results showed that Eu3+ singly doped KMg4(PO4)3 phosphor under UV excitation gives intense red emissions. The critical Eu3+ quenching concentration (QC) was determined to be 1.0 mol% along with excellent CIE coordinates of (0.6326, 0.3670). All the above results exhibits, the prepared phosphor is promising material as UV excitable red emitting phosphor for w-LED.

Luminescence properties and energy transfer mechanism of Eu3+ and Tm3+ Co-doped AlN thin films

Eu3+, Tm3+ co-doped AlN thin films have been prepared through ion implantation for the first time. The implanted samples were annealed at 1180 °C in N2 to recover implantation damages and activate the rare-earth ions. Luminescence properties were investigated by photoluminescence and cathodoluminescence spectra. Under 325 nm laser excitation, for both Eu3+-doped AlN and Eu3+, Tm3+ co-doped AlN, the sharp characteristic emission lines corresponding to intra-4fn-shell transitions of Eu3+ were observed, but no any emission peak associated to Tm3+ ion was observed. According to the cathodoluminescence spectra, both Eu3+ and Tm3+ ions can be excited efficiently under high-energy electron beam. For Eu3+, Tm3+ co-doped AlN, the cathodoluminescence emission intensity of Eu3+ and Tm3+ ions varies with the dose ratio of these two ions. A possible energy transfer mechanism between Tm3+ and Eu3+ is proposed. Through changing the dose ratio of Eu3+ respect to Tm3+ ions, the chromaticity coordinates and color temperatures could be effectively regulated.

Controllable hydrothermal synthesis and photoluminescence properties of CaGd2(WO4)4:Eu3+ red‐emitting phosphor

AbstractCaGd2(WO4)4:Eu3+ phosphors with controllable morphology were synthesized via the hydrothermal method. The influences of pH value, reaction time and Eu3+ concentration on the crystal structure, morphology, and photoluminescence properties of CaGd2(WO4)4:Eu3+ were studied. The pure tetragonal structure CaGd2(WO4)4 is obtained when the pH value is 8 and 9. Furthermore, by altering the pH value of the reaction solution, the morphologies of the CaGd2(WO4)4:Eu3+ phosphors evolve from spindle‐shaped grains to tetragonal plate‐like grains and finally to aggregated bulk particles. Under the 394 nm excitation, the phosphors display a bright red emission corresponding to the characteristic 4f‐4f transitions of Eu3+, and the intensity of emission peaks depends mainly on the pH value, the reaction time, and the Eu3+ concentration. The optimum photoluminescence performance is achieved for CaGd2‐x(WO4)4:xEu3+ (x = 1) phosphor synthesized at pH = 8 under the reaction time of 16 h. Finally, the thermal stability of the phosphors is analyzed at different ambient temperatures.

A white LED with orange-red phosphors KBaBP2O8:Eu3+

A series of phosphors K1+xBa1-2xBP2O8:xEu3+ (x = 0.04, 0.06, 0.08, 0.10, 0.12) were prepared by a simple solid-state reaction and the reaction process was carried out in the atmosphere. The phase composition and structure, sample morphology, luminescence performance, and thermal stability of K1+xBa1-2xBP2O8:xEu3+ were investigated by X-ray powder diffraction (XRD), scanning electron microscopic (SEM), and fluorescence spectrophotometer (PL). The XRD results indicate that the K1+xBa1-2xBP2O8:xEu3+ possessed the pure tetragonal system structure with a space group of I4¯2d. The excitation and emission spectra manifest that these phosphors can be effectively excited by the near-ultraviolet light, and exhibit an orange-red emission corresponding to the 5D0→7FJ (J = 1, 2) transitions of Eu3+. The optimum doping concentration of Eu3+ ions in K1+xBa1-2xBP2O8:xEu3+ was x = 0.10. The concentration quenching mechanism between the Eu3+ ions was determined as the dipole–dipole interaction host and the critical distance was procured to be 19.21 Å. The phosphors performed excellent properties between the temperature increased from 25 °C to 225 °C, and may become an orange-red phosphor with great potential in the lighting field.