Dominant Red Emission Research Articles

Highly Sensitive Temperature Sensors Resulting from the Luminescent Behavior of Sm3+-Doped Ba2MgMoO6 High-Symmetry Double-Perovskite Molybdate Phosphors.

We present double-perovskite molybdate with the formula of Ba2MgMoO6 doped with Sm3+ ions as a potential red phosphor to improve the color characteristics of white-light-emitting dioded (wLEDs). The new orange-red phosphor was synthesized using the co-precipitation (CP) method, and then its structural and spectroscopic properties were determined. Red emission at 642.6 nm dominates, which results from the electric dipole (ED) transition of the 4G5/2 → 6H9/2 type, and the materials are characterized by short luminescence decay times. BMM:Sm3+ is, to our best knowledge, the clearest example of dominant red emission of Sm3+ resulting from the location of the dopant in octahedral sites of high-symmetry cubic structure. In the sample containing 0.1% Sm3+, Sm3+ ions are located in both Mg2+ and Ba2+ sites, while at higher concentrations the Ba2+ site is less preferable for doping, as a result of which the emission becomes more uniform and single-site. The relative sensitivity calculated from FIR has a maximum of 2.7% K-1 at -30 °C and another local maximum of 1.6% K-1 at 75 °C. Such value is, to the best of our knowledge, one of the highest achieved for luminescent thermometry performed using only Sm3+ ions. To sum up, the obtained materials are good candidates as red phosphor to improve the color characteristics of wLEDs, obtaining a color-rendering index (CRI) of 91 and coordinated color temperature (CCT) of 2943 K, constituting a warm white emission. In addition to this, a promising precedent for temperature sensing using high-symmetry perovskite materials is the high sensitivity achieved, which results from the high symmetry of the BMM host.

Eu3+-activated NaBa4B3O9 phosphors toward multifunctional LED applications

Currently, most trivalent europium ion (Eu3+)-activated phosphors exhibit dominant red emissions at around 616 nm originating from 5D0 → 7F2 transition. However, recently, some works have indicated that Eu3+ ions could generate intense far-red emission (∼706 nm), which is assigned to the transition 5D0 → 7F4. Thus, utilization of the far-red emission from the transition 5D0 → 7F4 could expand the application fields of Eu3+-activated phosphors. Herein, we prepare a series of NaBa4-xB3O9:xEu3+ (x = 0.01, 0.05, 0.1, 0.15, and 0.2 mol) phosphors via the conventional solid-state reaction method. These phosphors possess dual intense emission at around 617 nm (5D0 → 7F2) and 706 nm (5D0 → 7F4) owing to Eu3+ ions occupying the distorted [BaO8] sites with C2 symmetry. Furthermore, owing to the dual emission, the NaBa4B3O9:Eu3+ phosphors could be used in various applications such as plant growth lighting or phosphor-converted white light emitting diodes.

Dominant red upconversion emission in LiErF4-based nanoparticles by reducing spontaneous emission of Yb3+

The achievement of dominant red upconversion emission by reducing spontaneous emission from Yb3+.

A novel narrow-band red-emitting multi-layer phosphor for white – Light emitting devices

SrZr2La2O7: Eu+3 (0.5–2.5 mol %) phosphors have been synthesized through the standard solid-state reaction technique. The photoluminescent and other structural properties such as PXRD (Powder X-ray Diffraction), SEM (Scanning Electron Microscopy) and Energy Dispersive X-ray spectroscopy (EDX), FTIR (Fourier transform infrared spectroscopy), PSD (Particle Size Distribution) of the phosphors were learned. The photoluminescence spectra show that the phosphor exhibited intense and dominant red emissions at 627 nm belonging to the 5D0 → 7F2 electric dipole transition. The FWHM of the red emissions at 627 nm is only 8.0 nm increasing in luminous efficacy. Hereby we propose a novel RED phosphor for RED emitting LEDs with phosphor-embedded polymer matrix layers of variable thickness and stacking up to 400 µm. The intensity of the red color was enhanced by self-excitation of photon absorption and emission. As a result, Eu3+doped SrZr2La2O7 phosphors can be widely used as red phosphors in UV chip-based WLEDs and displays. The phosphor exhibits high color purity up to 99% when excited at 590 nm. X-ray powder diffraction analysis confirms that the phosphor is highly crystalline and has a cubic phase.

Structural and photoluminescent features of Eu3+ activated single‐phase niobate phosphor for lighting applications

AbstractSingle‐phase barium sodium niobate phosphor (Ba2NaNb5O15: BNNO) doped with europium (Eu3+) ions have been synthesized by solid‐state reaction route. Pure and single‐phase formation with the tetragonal structure of the synthesized Eu3+‐doped BNNO (BNNO: Eu3+) phosphor was confirmed by X‐ray diffraction. The SEM image of BNNO sample indicates irregular morphology and nonuniform micron‐sized particle formation. The intense excitation peak located at 463 nm appeared in the excitation spectrum for BNNO: Eu3+ phosphors when monitored atred (615 nm) emission of Eu3+ ions. Under 463 nm excitation, the emission spectra for BNNO: Eu3+ exhibit dominant red (615 nm) emission peak. The luminescence intensity increases progressively up to the 10.0 mol% of Eu3+ ions and decreases further due to the concertation quenching effect. The energy transfer mechanism responsible for concentration quenching has been investigated in detail. The chromaticity coordinates assessed for BNNO: Eu3+ phosphors, which are located in the red region of Commission International de l'Eclairage 1931 diagram. The structural, morphological, and spectroscopic results attained for the synthesized phosphor (BNNO: Eu3+) demonstrate potential candidature as a red component phosphor in solid‐state lighting applications.

Blue-excited red emission of CeO2:Eu3+, Al3+ cubic phosphor: Influence of Al3+ ion doping and Judd-Ofelt theory

In this work, a series of CeO2: 0.1 Eu3+, xAl3+ (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5 mol %) red phosphors could be efficiently excited with blue-light was successfully prepared by solid-state reaction. The X-ray diffraction confirmed the formation of a single-phase CeO2 cubic with high crystallinity. Under blue light (466 nm) excitation, the CeO2: Eu, Al phosphors showed dominant red emission of Eu3+ ions associated with 5D0 – 7F2 transition, which matched well with the commercial blue light InGaN chip. Significantly, the red emission intensity of sample co-doped with 0.3% mol Al3+ was enhanced by 8-times compared to the un-doped one. This result was caused by the presence of Al3+ ions forming oxygen vacancies and disturbing the symmetry of the host, leading to effectively enhanced red emission of the system. The enhanced red emission mechanism of the CeO2:Eu3+, Al3+ phosphors was further explained by Judd-Ofelt (J-O) theory analysis and radiative properties, including branching ratios (βr), transition probability (A), radiative lifetime (τcal), and stimulated emission cross-section (σe) of the phosphor were determined. The CeO2:0.1Eu3+, 0.3Al3+ phosphor shows intense red emission, a long lifetime (0.735 ms), and high quantum efficiency (49.46%), making it a suitable candidate as a red component for preparing low-cost WLEDs.

High-efficiency energy transfer in the strong orange-red-emitting phosphor CeO2:Sm3+, Eu3.

High-efficiency energy transfer (ET) from Sm3+ to Eu3+ leads to dominant red emission in Sm3+, Eu3+ co-doped single-phase cubic CeO2 phosphors. In this work, a series of Sm3+ singly and Sm3+/Eu3+ co-doped CeO2 cubic phosphors was successfully synthesized by solution combustion followed by heat treatment at 800 °C in air. The crystal structure, morphology, chemical element composition, and luminescence properties of the obtained phosphors were investigated using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and photoluminescence analysis. Under 360 nm excitation, the Sm3+ singly doped CeO2 phosphor emitted strong yellow-red light at 573 nm (4G5/2-6H5/2) and 615 nm (4G5/2-6H7/2). Meanwhile, the CeO2:Sm3+, Eu3+ phosphors showed the emission characteristic of both Sm3+ and Eu3+, with the highest emission intensity at 631 nm. The emission intensity of Sm3+ decreased with increasing Eu3+ content, suggesting the ET from Sm3+ to Eu3+ in the CeO2:Sm3+, Eu3+ phosphors. The decay kinetics of the 4G5/2-6H5/2 transition of Sm3+ in the CeO2:Sm3+, Eu3+ phosphors were investigated, confirming the high-efficiency ET from Sm3+ to Eu3+ (reached 84%). The critical distance of energy transfer (RC = 13.7 Å) and the Dexter theory analysis confirmed the ET mechanism corresponding to the quadrupole-quadrupole interaction. These results indicate that the high-efficiency ET from Sm3+ to Eu3+ in CeO2:Sm3+, Eu3+ phosphors is an excellent strategy to improve the emission efficiency of Eu3+.

A novel red-emitting Na5W3O9F5:Eu3+ phosphor with high color purity for blue-based WLEDs

Red phosphor plays a key role in improving the lighting and display quality of phosphor-converted white light-emitting diodes (pc-WLEDs). Meanwhile, developing new luminescent matrix materials can positively contribute to the acquisition of ideal and efficient phosphors. In this work, we propose a novel red-emitting Na5W3O9F5:Eu3+ (NWOF:Eu3+) phosphor. The phase composition, morphology, electronic structure and photoluminescence properties of the NWOF:Eu3+ phosphor were systematically investigated. The EXAFS results prove that the Eu3+ dopants occupy the Na2 and Na3 sites in the NWOF host. Under 466 nm blue light excitation, NWOF:xEu3+ (0.05 ≤ x ≤ 0.25) phosphors display a dominant red emission at 607 nm and achieves a high color purity (97.44%) due to the dominant electric dipole transition (5D0→7F2) of Eu3+ ions. Impressively, this red-emitting NWOF:0.25Eu3+ phosphor exhibits relatively superior thermal stability (450 K, >50%) and excellent chromaticity stability (2.32 × 10−4 ≤ ΔE ≤ 6.23 × 10−3) from 298 K to 498 K. The activation energy for thermal quenching effect is determined to be 0.22 eV. Moreover, the pc-WLED was fabricated by coupling a 460 nm blue chip with the as-synthesized NWOF:0.25Eu3+ red phosphor and commercial YAG:Ce3+ phosphor. The optical parameters of the as-fabricated pc-WLED are also measured, and the CIE coordinates remain almost constant as the drive current increases from 20 mA to 120 mA. These results indicate that the NWOF:0.25Eu3+ red phosphors should be a suitable candidate as a red component for the preparation of pc-WLEDs.

Template-free microwave-assisted growth of 3D hexagonal ZnO rods

Here, a rapid synthesis method for growing template-free three-dimensional hexagonal zinc oxide (ZnO) micro-rods (HZMR) using a pulsed-microwave (p-MW) irradiation technique is reported. The effects of microwave exposure time and power are shown to tune the morphology of hexagonal rods from solid to blind hole to hollow rods. X-ray diffraction (XRD) confirmed the growth of pure ZnO phase. Morphological investigations by Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM), optical properties by micro-Raman, Diffuse Reflectance Spectroscopy (DRS), Attenuated Total Reflectance (ATR) and Photoluminescence (PL) spectroscopy techniques were carried out. The PL studies reveal a dominant red emission along with characteristic blue and green emissions. The resulting structures have the scope of being applied as miniature sensors or in lasing applications. The blind-holed structures can be used as miniature crucibles/pots in reactions. This template-free growth of hexagonal rods is a very simple and economical technique that can result in solid, hollow or one-end blind hexagonal rods. The paper discusses the growth mechanism of these unique hierarchical HZMR.

Novel BaY1-xGdxF5: Yb3+/Er3+/Bi3+ solid solution nanocrystals with enhanced upconversion luminescence and magnetism properties

Fluoride phosphors with enhanced upconversion luminescence performance and multi-functionalization are urgently explored for applications in modern bio-detection and medical imaging. Here, a series of BaY1-xGdxF5: Yb/Er/Bi (0 ≤ x ≤ 0.5) solid solution nanocrystals are designed and synthesized. The influence of Gd3+-doping concentration on microstructure, upconversion luminescence, and magnetic performances are deeply reported. XRD results demonstrate the formation of solid solution with cubic phase structure. With increasing Gd3+ concentration, the diffraction angle gradually shifts toward lower direction as a result of replacing Y3+ by Gd3+ with larger ionic radius. Microstructure results show that the size distribution is between 60 and 100 nm and reveal that Gd3+ facilitates the growth of crystal grains. Upon 980 nm excitation, the BaY1-xGdxF5: Yb/Er/Bi samples demonstrate two dominant green and red emissions of Er3+ at 546 nm and 658 nm, respectively. By substituting Y3+ with Gd3+, the characteristic green luminescence can efficiently lead to an obvious enhancement at x = 0.2. The detailed enhancement mechanism is presented. Besides, the obtained nanocrystals show excellent paramagnetism properties, and the magnetic magnitude is significantly enhanced with increasing Gd3+ concentration. These results indicate that the BaY1-xGdxF5: Yb/Er/Bi nanocrystals are promising three-mode probes with potential applications in medical imaging and disease diagnosis.

Red, Green, Blue and IR emitting zirconium Titanate nano composite co-doped with Er3+/Tm3+/Yb3+ synthesized by combustion synthesis

Activation of upconversion emission in visible region and emission in infrared region in tri-codoped (Er3+, Tm3+ and Yb3+ rare earth ions) zirconium titanate nano composites has been attained by synthesizing through solution combustion method. ZrTi1.4O4, serves as host matrix which offers lowest phonon energy at 870 cm−1. PL emission has been recorded by exciting the samples with wavelength of 980 nm in NIR region. X-Ray diffraction patterns confirm crystallinity of the composites. Morphological studies were performed by Field emission scanning electron microscopy. Primary colors, Blue (475 nm), green (520 nm, 530 nm, 540 nm and 550 nm) and red (650 nm and 670 nm) emissions in visible region along with IR emission peaks centered at 1531 nm, 1574 nm, 1646 nm, 1738 nm and 1793 nm were observed. Dominant red emission appearing in the PL spectra is regarded to be due to Multi phonon relaxation and cross relaxations.

Systematic Analysis of the Crystal Chemistry and Eu3+ Spectroscopy along the Series of Double Perovskites Ca2LnSbO6 (Ln = La, Eu, Gd, Lu, and Y).

Eu3+ (1 mol %)-doped Ca2LnSbO6 (replacing Ln3+; Ln = Lu, Y, Gd, and La) and Ca2EuSbO6 were synthesized and structurally characterized by means of X-ray powder diffraction. The Eu3+ luminescence spectroscopy of the doped samples and of Ca2EuSbO6 has been carefully investigated upon collection of the excitation/emission spectra and luminescence decay curves of the main excited states. Surprisingly, apart from the dominant red emission from 5D0, all the doped samples show an uncommon blue and green emission contribution from 5DJ (J = 1, 2, and 3). This is made possible thanks to both multiphonon and cross-relaxation mechanism inefficiencies. However, the emission from 5D3 is more efficient and the decay kinetics of the 5DJ (J = 0, 1, and 2) levels is slower in the case of Y- and Lu-based doped samples. This evidence can find a possible explanation in the crystal chemistry of this family of double perovskites: our structural investigation suggests an uneven distribution of the Eu3+ dopant ions in Ca2YSbO6 and Ca2LuSbO6 hosts of the general A2BB′O6 formula. The luminescent center is mainly located in the A crystal site, and on average, the Eu–Eu distances are longer than in the case of the Gd- and La-based matrix. These longer distances can further reduce the efficiency of the cross-relaxation mechanism and, consequently, the radiative transitions are more efficient. The slower depopulation of Eu3+ 5D2 and 5D1 levels in Ca2YSbO6 and Ca2LuSbO6 hosts is reflected in the longer rise observed in the 5D1 and 5D0 decay curves, respectively. Finally, in Ca2EuSbO6, the high Eu3+ concentration gives rise to an efficient cross-relaxation within the subset of the lanthanide ions so that no emission from 5DJ (J = 1, 2, and 3) is possible and the 5D0 decay kinetics is faster than for the doped samples.

Novel narrow band red emitters based on mixed metal oxides and their application in hybrid white light-emitting diodes.

A series of high-efficiency narrow band red-emitting La2 M2 O9 :Eu3+ (M = Mo/W) phosphors for white LEDs was synthesized using a conventional solid-state reaction method. All the compositions show absorption in the near ultraviolet (UV) light region due to charge transfer from O to M (M = W and Mo). In order to investigate the luminescence quenching effect, the Eu3+ concentration was varied in the La2 M2 O9 lattice. The tungstate analogue had a quantum yield of 46.5%, whereas the molybdate equivalent had a comparatively subordinate value (15.4%). The phosphor could be competently excited by ~395 or 465 nm photons (could be integrated well with a near-UV or blue LED chip) and showed dominant red emission electric-dipole transition (5 D0 →7 F2 ) with sharp spectral lines due to 4f-4f electronic transition of the Eu3+ ion and potential red-emitting colour converters for white LEDs. The red LED was fabricated by integrating the best phosphor composition with a near-UV LED and a white hybrid LED was fabricated by conjugating with a yellow organic dye and a red phosphor with near-UV LEDs. The white hybrid LED showed an excellent colour rendering index (83%), with CIE colour coordinates (0.313, 0.365) and CCT (6280 K).

Efficient Energy Transfer from Trap Levels to Eu3+ Leads to Antithermal Quenching Effect in High-Power White Light-Emitting Diodes.

The most critical aspect in the assembly of phosphor-converted white light-emitting diodes (pc-WLEDs) is how to stabilize the device in a practical environment. The high applied currents can generate enormous heat up to more than 100 °C, and such a continuous illumination process will lead to serious effects concerning the stability of the device. Therefore, the new search for examples to fully suppress thermal quenching effect is a real challenge. In this study, a novel Eu3+-activated CaMgGeO4 (CMGO) phosphor of olivine type is developed via a conventional solid-state reaction. The results reveal that Eu3+ occupies the low symmetric Ca2+ site of this host. Upon visible-light sensitization at 464 nm, a dominant red emission band with maximum at 612 nm is witnessed. Its full width at half-maximum (fwhm) is merely ∼4.37 nm, and a high color purity of around 94% is achieved. Their corresponding Commission Internationale de L'Eclairage (CIE) coordinates are very close to standard red color coordinates (0.666, 0.333). The influence of concentration and temperature on the optical property has been explored. It has been discovered that the optimized sample (CMGO:0.01Eu3+) is not influenced by the thermal quenching effect and its fluorescent intensity is improved even up to 473 K, which is mainly attributed to the incorporation of abundant trap sites generated by the nonequivalent substitution Eu3+ for Ca2+. After it is integrated into commercially available YAG:Ce3+ phosphor-based pc-WLEDs, the excellent optical parameters of the fabricated WLEDs are evaluated. The correlated color temperature (CCT) varies from cool white (6458 K) to warm (4370 K), and the color rendering index (CRI) increases from 78 to 86 under a high flux operating current of 200 mA. Furthermore, the chromaticity coordinates remain almost stable with the increasing drive current from 200 mA to 1000 mA. It is highly expected that CaMgGeO4:0.01Eu3+ will become a suitable red phosphor for the preparation of white LEDs with high efficiency.

High thermal stability and color purity of red-emitting phosphor Y2SiWO8: Eu3+ for w-LEDs: Synthesis and photoluminescence properties

A series of Eu3+-activated Y2SiWO8 red phosphors were prepared using the sol-gel process. The as-synthesized phosphors were characterized by X-ray diffraction, crystal structure, morphology as well as photoluminescence spectra. Observed from the excitation spectrum, Y2SiWO8: Eu3+ phosphor exhibits the highest excitation peak situated at ∼395 nm. Excited by 395 nm, this phosphor presents the dominant red emission band (∼619 nm), arising from the electric dipole transition 5D0→7F2 of Eu3+. The optimum Eu3+ dopant concentration is 6 mol%, beyond which the concentration quenching happens. The energy immigration mechanism among Eu3+ ions is extensively studied, which further proves to be the dipole-dipole interaction. More importantly, this phosphor is found to emit a bright red light with the excellent color coordinate (0.665, 0.335) and color purity (96.61%) under the excitation of n-UV light. The phosphor exhibits remarkable thermal stability and its emission intensity remains above 80% at 473 K, as compared to that at room temperature. Furthermore, the structural and optical properties of as-obtained microcrystal phosphors are thoroughly investigated as a function of the [MoO4] content. It can be concluded that Y2SiWO8: Eu3+ phosphors have a great promising in the field of n-UV pumped w-LEDs.

Bright tunable white-light emissions from Bi3+/Eu3+ co-doped Ba2Y5B5O17 phosphors via energy transfer for UV-excited white light-emitting diodes

Single-phased tunable white-emitting inorganic phosphors are important for fabricating high-performance white light-emitting diodes. Herein, we reported on the realization tunable white emissions from Bi3+ and Eu3+ ions co-doped Ba2Y5B5O17 phosphors by controlling the energy transfer process from Bi3+ to Eu3+ ions. In this paper, Bi3+ singly doped Ba2Y5B5O17 and Bi3+/Eu3+ co-doped Ba2Y5B5O17 phosphors were synthesized through the conventional high-temperature solid-state reaction method. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), elemental mapping, photoluminescence (PL), and CIE color coordinates. Upon excitation by ultraviolet (UV) light at 345 nm, Bi3+ singly doped Ba2Y4.995Bi0.005B5O17 phosphors showed a broadband cyan emission with a maximum at 503 nm and a shoulder at 410 nm, due to 3P1→1S0 transition of Bi3+ ions. Concentration-dependent PL intensity study revealed that the Ba2Y5-xBixB5O17 phosphors had highest emission intensity at x = 0.005. In contrast, the Eu3+ singly doped Ba2Y4.2Eu0.8B5O17 phosphors exhibited dominant sharp red emission lines around 616 nm upon 396 nm UV excitation. Interestingly, efficient energy transfer from Bi3+ to Eu3+ ions was observed in Bi3+/Eu3+ co-doped Ba2Y4.995-yEuyBi0.005B5O17 phosphors. Consequently, after excitation at 345 nm into the Bi3+1S0→3P1 transition, the Ba2Y4.995-yEuyBi0.005B5O17 phosphors showed intense sharp red emissions around 611 nm of Eu3+ ions together with a broad cyan emission band centered at 410 nm and 503 nm due to Bi3+ ions. By changing the Eu3+/Bi3+ concentration ratio, tunable white emissions were achieved in Ba2Y4.995-yEuyBi0.005B5O17 phosphors. The corresponding CIE chromaticity coordinates of Ba2Y4.995-yEuyBi0.005B5O17 phosphors were tuned from cyan color (0.226, 0.350) to near white (0.309, 0.354) and ultimately to red color (0.640, 0.341) by gradually increasing the doping concentration of Eu3+ ions. Our results demonstrated that these as-prepared Bi3+/Eu3+ co-doped Ba2Y5B5O17 phosphors had promising application potential in UV-excited white light-emitting diodes.

Er3+ activated and Yb3+ sensitized upconversion photoluminesecse in zirconium titanate nano powders

Effective UC-PL by IR to visible conversion of photons by incorporating Er3+ and Yb3+ in ZrTi1·4O4 nano composite is studied and summarised. The nano powders were synthesized by wet chemical method i.e. solution combustion synthesis with urea as fuel. X-Ray diffraction analysis of the sample designates the effective incorporation of the Er3+ and Yb3+ ions into the host matrix. Phonon energy is as low as 870 cm−1 for ZrTi1·4O4 as confirmed by Raman analysis guarantees it to be promising matrix for upconversion photoluminescence. Strong green and red emission could be observed for ZTi1.4O4 doped with Er3+ and Yb3+ were attributed to 2H11/2 → 4I15/2,4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions respectively. Multi phonon relaxation and cross relaxation contribute for dominant red emission.

New self charge compensating perovskite type red phosphors prepared via ball milling process for pc-white light emitting diode applications

New self charge compensating red emitting perovskite type phosphors, Na(1+x)Ca(1-2x)TiNbO6:x Eu3+ were prepared by a high energy ball milling method and subsequent calcination process in the temperature range 1000–1200 °C. Their structural, morphological and optical properties were studied by advanced characterization tools. The X-ray diffraction analysis confirms the formation of orthorhombic type structure with a space group Pnma. These phosphors exhibit intense red emission due to forced electric dipole transition, 5D0→7F2 under near UV (395 nm) and blue (463 nm) excitations. The dominant red emission with high asymmetry ratio further evidences the occupancy of Eu3+ at the non-centrosymmetric A site of the perovskite. The high concentration quenching (20 mol%.) is observed in the system due to layered ordering of the A site cations occupied by Eu3+ion also. The photoluminescence properties of these phosphors were optimized with calcination temperature. Morphological observation reveal increase in the grain size of the phosphor particles with calcination temperature. The optimum phosphor properties were found at 1100 °C and beyond that quenches the luminescence. Also the comparison of photoluminescent emission of commercial red phosphor Y2O3: Eu3+with our prepared optimized phosphor Na(1.2)Ca(0.8)TiNbO6: 0.2Eu3+ (1100 °C) was carried out. We got very good emission intensity in comparison with the commercial one. The calculated CIE color co-ordinates and Correlated Color Temperature are (0.65, 0.33) and 2799 K respectively, also we got excellent color purity value of 94%. The obtained results suggest that the developed red phosphors are potential candidates for white light emitting diode (WLED) applications.

Ultrafast preparation of Europium(III) and Terbium(III) activated LaSr2F7 nanoparticles for white LEDs and anti-counterfeiting mark

Tunable color-emitting LaSr2F7 nanoparticle-based phosphor materials with single- or co-doped trivalent rare-earth ions (Eu3+/Tb3+) were synthesized via an ultrafast chemical precipitation technique. When Eu3+ and Tb3+ ions were doped into the LaSr2F7 nanoparticles, the photoluminescence behaviors were investigated and showed characteristic red and green emissions in their respective regions. Under 393 nm excitation, the LaSr2F7:xEu3+ nanoparticles revealed the dominant red emission band (5D0 → 7F1) of Eu3+ ions while the optimum doping concentration was obtained at 0.4 mol, indicating a quantum yield (QY) of 24.5%. Likewise, the LaSr2F7:yTb3+ nanoparticles showed the f-f transition of Tb3+ ions and an intense green-emission peak at 543 nm (5D4 → 7F5) was observed under 352 nm of excitation wavelength and the predominant doping concentration was 0.5 mol and the QY was estimated to be about 33.4%. By increasing the Eu3+ ion concentration in the optimized LaSr2F7:Tb3+ phosphors, the color emissions were turned from yellow to red under 365 nm excitation and the existed energy transfer efficiency in between the Tb3+ and Eu3+ ions was analyzed. Furthermore, the red-, green- and warm white-emitting devices were also fabricated by utilizing the optimal single- and co-doped samples for covering NUV chips. Ultimately, the LaSr2F7:Eu3+ and LaSr2F7:Tb3+ nanoparticles were further applied to a high-security ink for stabile anti-counterfeiting mark.

Enhancement of photoluminescence properties of Y0.95(P0.6V0.4)O4:Eu0.05 phosphors by doping Al3+ ions

This paper reports an approach for improving the photoluminescence characteristics of red-emitting Y0.95(P0.6V0.4)O4:Eu0.05 phosphors, with the incorporation of Al3+ ions, using a chemical co-precipitation process. In this paper, structural, scanning electron microscopic (SEM), photoluminescence properties, infrared spectroscopy, and CIE of the Y0.95−x(P0.6V0.4)AlxO4:Eu0.05 (x = 0.0, 0.005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035) phosphors are reported. The doping of a small amount of Al3+ ions to Y0.95−x(P0.6V0.4)AlxO4:Eu0.05 phosphors significantly enhanced the emission intensity up to x = 0.025%. The most dominant red emission intensity peak of Eu3+ for 5D0 → 7F2 transition of the Y0.975(P0.6V0.4)Al0.025O4:Eu0.05 phosphor is located at 622 nm, which is stronger than that of the free Al3+ Y0.95(P0.6V0.4)O4:Eu0.05 phosphor. The result shows that this phosphor has a certain amount of the application prospect of the white LED.