CIE Diagram Research Articles

Energy transfer investigation of Sm3+/Eu3+ CaBAl glasses

Sm3+/Eu3+ codoped CaBAl glasses were prepared by conventional melt-quenching method, and their structural and optical properties were studied. The values of volumetric density and electronic polarizability showed an increase with the addition of Sm2O3. The Fourier-transform infrared spectroscopy (FTIR) spectra indicated the existence of trigonal and tetrahedral borate groups. The N4 values revealed that Sm2O3/Eu2O3 codoping favored the conversion of structural units from BO4 to BO3. The observed absorption bands in UV/VIS spectra were attributed to Eu3+ and Sm3+ transitions, from the ground states 7F0 and 6H5/2 to the various excited states. Color coordinates at CIE diagram were studied for the codoped glasses upon exciting at 405 nm. The energy transfer from the level 4G5/2 of Sm3+ to the 5D0 level of Eu3+ was verified by means of the luminescence results. With the addition of Sm3+, emission intensity of Eu3+ has been enhanced due to migration of Sm3+ excitation energy. The mechanism for energy transfer from Sm3+ to Eu3+ was investigated by Dexter energy transfer formula and Reisfeld's theory application on photoluminescence decay curves. A decrease in the lifetime of 4G5/2 → 6H7/2 transition was observed when Sm3+ was increased, probably due to ion-ion interaction and excitation energy migration.

Enhanced photoluminescence via doping of phosphate, sulphate and vanadate ions in Eu3+ doped La2(MoO4)3 downconversion phosphors for white LEDs

In this study, the Eu3+ doped La2(MoO4)3 phosphor has been successfully prepared by solid state reaction method. The prepared phosphors are crystalline and the particle size increases in the presence of phosphate, sulphate and vanadate ions. The photoluminescence excitation (PLE) spectrum of the Eu3+ doped La2(MoO4)3 phosphor shows an intense peak centered at 467 nm due to absorption by Eu3+ ions. On the excitation at 467 nm, the Eu3+ doped La2(MoO4)3 phosphor emits strong red emission centered at 614 nm, which is attributed to the 5D0 → 7F2 transition of Eu3+ ions. The emission intensity of the phosphors has been optimized by appropriate selection of the concentration of Eu3+ ions. When the phosphate, sulphate and vanadate ions are incorporated in the thermally stable Eu3+ doped La2(MoO4)3 phosphor the emission intensity of Eu3+ion is enhanced significantly. This occurs due to modification in the local crystal structure and the particle size increase. The CIE diagram shows the presence of emission bands in the visible spectrum. It also shows color tunability with a high color purity of the phosphor. The phosphate, sulphate and vanadate doped La2(MoO4)3: Eu3+ phosphors may act as good candidates for the phosphor converted white LEDs in solid state lighting technology.

Concentration Dependent Luminescence and Energy Transfer Properties of Samarium Doped LLSZFB Glasses

Background: Recently, great importance has been devoted to borate glass systems doped with rare-earth ions because of their unique peculiar properties in the field of photonics for optical applications. Objective: The purpose of the present study is to investigate the effect of concentration of Sm3+ ions on the luminescence properties of lead fluoroborate glasses through the energy transfer mechanism. Materials and Methods: Samarium doped lead fluoroborate glasses with chemical composition 20PbF2 .10Li2O .5SrO .5ZnO. (60-x) B2O3. xSm2O3 (where x = 0.1, 0.5, 1.0, 1.5 and 2.0 mol %) were prepared by means of melt quenching method. The concentration dependent luminescence properties were investigated in detail from the optical absorption, photoluminescence and decay analysis. Judd-Ofelt (J-O) theory was applied to analyze the optical absorption spectra. The experimental oscillator strengths of absorption bands have been used to determine the J-O parameters. Using the J-O parameters Ωλ (λ = 2, 4 and 6) and luminescence data several radiative parameters were obtained. Results: From the luminescence spectra, it was noticed that luminescence quenching starts at higher concentrations of Sm3+ ions (x ≥ 0.5 mol %). The decay curves of 4G5/2 → 6H7/2 transition exhibit a single exponential at lower dopant concentrations (x= 0.1 and 0.5 mol %) and non-exponential at higher concentrations (x ≥ 1 mol %). The concentration quenching was attributed to the energy transfer through the cross-relaxation between Sm3+ ions. The non-exponential curves were well fitted to Inokuti-Hirayama model for S = 6, indicating that the energy transfer between Sm3+ - Sm3+ ions is of dipole-dipole type. The calculated color coordinates of the as-prepared glasses fall within the reddish-orange region of the CIE diagram. Conclusion: All the experimental results indicate that the 0.5 mol% Sm3+ ions doped LLSZFB glass can be a possible choice for solid state lighting and display applications.

Development of ZnO–BaO–B2O3–TeO2 glass doped with Sm3+ for orange emitting material

Zinc barium borotellurite glass samples were synthesized with the chemical composition of 10ZnO–30BaO–30B2O3-(30-x)TeO2-xSm2O3 (where 0.05 ≤ x ≤ 1.50 in mol%). Several techniques for XRD, FTIR, absorption, luminescence and decay time measurements were used to investigate the structural and spectroscopic properties. It was found that the XRD patterns revealed amorphous nature of the glass samples. The structural modification of (TeO4) trigonal bipyramid structural units was observed using FTIR spectroscopy. The UV–VIS–NIR absorption spectra displayed seven absorption peaks corresponding to the energy transitions from the ground level 6H5/2 to 6F11/2 (947 nm), 6F9/2 (1085 nm), 6F7/2(1238 nm), 6F5/2 (1385 nm), 6F3/2 (1492 nm), 6H15/2 (1550 nm), and 6F1/2 (1589 nm) excited levels of Sm3+ ion. For the emission spectra, four peaks revealed the transitions 4G5/2 → 6H5/2 (563 nm), 6H7/2 (601 nm), 6H9/2 (644 nm) and 6H11/2 (705 nm). The phenomenological intensity parameters Ωλ (λ = 2, 4, 6) according to Judd–Ofelt theory were calculated. The J-O parameters have been used to forecast several radiative properties such as transition probability (AR), branching ratio (βR) and stimulated emission-cross-sections (σp) in 4G5/2 excitation level of samarium ion. The decay patterns of the 4G5/2 level were fitted using non exponential as well as Inokuti–Hirayama (IH) model. The luminescence spectra of Sm3+ ion of the glasses was analyzed with The CIE chromaticity color coordinates. According to the CIE coordinates, it was located in the boundary of orange light in the CIE diagram. All of the results indicated that these glass compositions could be used for preparing a material which will be a potential candidate for laser applications.

Effect of singly, doubly and triply ionized ions on downconversion photoluminescence in Eu3+ doped Na2Sr2Al2PO4Cl9 phosphor: A comparative study

We report a change in the red photoluminescence of the Eu3+ doped Na2Sr2Al2PO4Cl9 phosphor via doping of singly, doubly and triply ionized ions. The synthesized phosphors show good crystalline nature. The EDS analysis confirms the presence of desired elements in the phosphor samples. The vibrational feature of the phosphor was confirmed by FTIR analysis. The photoluminescence excitation spectra of the phosphor show three peaks at 317, 395 and 467 nm. The Eu3+ doped Na2Sr2Al2PO4Cl9 phosphor emits intense red color on excitations with 395 and 467 nm wavelengths. However, the photoluminescence intensity of the phosphor is larger for 395 nm excitation. When the singly, doubly and triply ionized ions are co-doped in the Eu3+ doped Na2Sr2Al2PO4Cl9 phosphor (i.e. F−, WO42−, MoO42−, VO43−, La3+, and Y3+) the photoluminescence intensity of the phosphor is decreased significantly. The decrease in photoluminescence intensity is due to change in local crystal structure created by these ions. Interestingly, the photoluminescence intensity of phosphor increases many times when the (Y3+) ion incorporated phosphor is excited with 317 nm wavelength. The CIE diagram shows color emitted in the red region of visible spectrum and the color purity is larger for triply ionized (Y3+) ion. Thus, the singly, doubly and triply ionized ions activated Na2Sr2Al2PO4Cl9: Eu3+ phosphor may be used in displays devices, photonic devices, solid state lighting and white LEDs.

Effect of TiO2 doping on structural and optical properties of CdSZn3(PO4)2 nanocomposites

Pure and (0.3, 0.6 and 0.9 mol%) TiO2-doped CdSZn3(PO4)2semiconducting nanocomposites were successfully synthesized by hydrothermal route. The structural compositions, surface morphology, diffuse reflectance spectroscopy and luminescence properties of all the nanocomposites were systematically investigated. X-ray diffraction pattern exhibits the co-existence of both hexagonal phase of CdS and a mixer of γ and β monoclinic Zn3(PO4)2 phases with high crystalline order. Upon increasing of TiO2 content from 0.3 to 0.9 mol%, γ-Zn3(PO4)2 phase is decreasing while β-Zn3(PO4)2 phase is found to increase. Further, it has been found that the TiO2 additive atoms did not segregate to form secondary phases but led to variation in grain size, local disorder and local strain in the nanocomposites. The average crystallite size of nanocomposites is in the range 22–25 nm. The surface morphology of the samples was clearly shown as flakes surrounded by hexagonal CdS spheres like heterostructure type morphology. EDAX results confirm the stoichiometry of all the samples with slight variation of CdS content with increasing TiO2 dopant content. Optical band gap values are found to decrease from 2.52 to 2.44 eV with increasing TiO2 content. Further, photoluminescence studies revealed that all the samples exhibited strong fluorescence in the visible wavelength region and the chromaticity characteristics from CIE diagram were also explored in search of their applicability for commercial LED applications.

Microwave sol-gel synthesis, microstructural and spectroscopic properties of scheelite-type ternary molybdate upconversion phosphor NaPbLa(MoO4)3:Er3+/Yb3+

New ternary molybdate NaPbLa(1-x-y)(MoO4)3:xEr3+,yYb3+ (x = y = 0, x = 0.05 and y = 0.35, 0.4, 0.45 and 0.5) phosphors were successfully fabricated by the MSG (microwave sol-gel) method, and the microstructural and spectroscopic properties were characterized. The crystal structure of NaPbLa(MoO4)3 (NPLM) was defined by Rietveld analysis in space group I41/a with unit cell parameters a = 5.3735(2) and c = 11.8668(4) Å, V = 342.65(3) Å3, Z = 4 (RB = 6.64%). The unit cell volume of NaPbLa(MoO4)3 (NPLM) was intermediate between those of NaLa(MoO4)2 and PbMoO4. Under the 980 nm excitation, upconverted yellowish-green emissions at transitions from 2H11/2 and 4S3/2 were observed. No concentration quenching in the subsystem of donor ions at the content up to 50 at.% and no cross-relaxation losses in the subsystem of acceptor ions at the concentrations as high as 5 at. % were verified. The individual chromaticity points for the NaPbLa(MoO4)3:Er3+,Yb3+ phosphors, corresponding to the equal-energy point in the standard CIE diagram, revealed yellowish-green emissions.

Near UV excited multi-color photoluminescence in RE3+ (RE=Tb, Sm, Dy and Eu) doped Ca2Pb3(PO4)3Cl phosphors

The Ca2Pb3(PO4)3Cl: RE3+ (RE = Tb, Sm, Dy and Eu) phosphor materials were prepared by wet chemical method. The synthesized phosphors were analyzed by using XRD, SEM and photoluminescence (PL) characterization techniques. The excitation spectrum of the Ca2Pb3(PO4)3Cl:Tb3+ phosphor consists of several bands in the 300–400 nm region by monitoring emission at 545 nm, which are assigned due to electronic transitions from 7F6 to the upper levels of Tb3+ ion. The Ca2Pb3(PO4)3Cl:Tb3+ phosphor emits efficient narrow green emission at 545 nm due to 5D4 → 7F5 transition upon 371 nm excitation. The PL excitation spectrum of the Ca2Pb3(PO4)3Cl:Sm3+ phosphor exhibits narrow bands in the near ultraviolet (NUV) region due to Sm3+ ion. The Ca2Pb3(PO4)3Cl: Sm3+ phosphor shows orange red emission centered at 598 nm, which is attributed to the 4G5/2 → 6H7/2 transition of Sm3+ ion. The concentration quenching has been studied in both the cases and the critical distance was calculated as 38.5 Å. The blue (482 nm) and yellow (576 nm) emissions are obtained in the Ca2Pb3(PO4)3Cl:Dy3+ phosphor under 352 nm and 455 nm excitations, which are attributed to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+ ion, respectively. However, the Ca2Pb3(PO4)3Cl:Eu3+ phosphor emits strong orangish red emission centered at 594 nm, which is attributed to the 5D0 → 7F1 transition of Eu3+ ion on excitation with 396 nm. The CIE diagram shows green and orange red photoluminescence for the Ca2Pb3(PO4)3Cl:Tb3+ and Ca2Pb3(PO4)3Cl:Sm3+ phosphors, respectively whereas the bluish-yellow and orangish red photoluminescence for the Ca2Pb3(PO4)3Cl:Dy3+ and Ca2Pb3(PO4)3Cl:Eu3+ phosphors, respectively. The CIE coordinates indicate that the present phosphors have high color purity. These phosphors may act as good candidates for phosphor converted LEDs for solid state lighting technology.

Synthesis and Research of rare earth-doped color tunable Sr3Gd(PO4)3 phosphors

Rare earth-doped Sr3Gd(PO4)3 and emission color tunable phosphors Ce[Formula: see text]/Sm[Formula: see text] co-doped Sr3Gd(PO4)3 have been synthesized by a traditional solid-state method. These phosphors were characterized by X-ray diffraction (XRD), FE-SEM, diffuse reflectance spectra (DRS), photoluminescence spectra and lifetime measurements. The quenching concentration of Ce[Formula: see text] ions in Sr3Gd(PO4)3 was about 9 mol.%. An effective energy transfer (ET) from Ce[Formula: see text] ions to Sm[Formula: see text] ions in Sr3Gd(PO4)3 was speculated by the overlapped spectrum for the emission peak of Ce[Formula: see text] and the excitation peak of Sm[Formula: see text] ions. It is demonstrated that the ET mechanism is resonant through the dipole–dipole interaction and the critical distance between Ce[Formula: see text] and Sm[Formula: see text] in Sr3Gd(PO[Formula: see text] is calculated to 15.22 Å. Moreover, Sr3Gd[Formula: see text](PO4)3:0.09Ce[Formula: see text], xSm[Formula: see text] can be adjusted systematically by generating blue light to white light in the CIE diagram which coincide with the ET process of Ce[Formula: see text] ions to Sm[Formula: see text] ions. The Sr3Gd[Formula: see text](PO4)3:0.09Ce[Formula: see text], 0.01Sm[Formula: see text] phosphor also perform at a good thermal stability. All of these experimental results in this work can be served as a potential multicolor tunable phosphor for ultraviolet pumped white light appliance.

Preparation and characterization of Luminescent nanostructured Gd2O3-Y2O3:Eu synthesized by the solution combustion process

Abstract Microwave-assisted combustion of Europium doped Y2O3–Gd2O3 was investigated using glycine, glucose, glycerol and citric acid as organic fuel. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) pattern, Brunauer–Emmett–Teller (BET) method, X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL) techniques were used to characterize the nanostructured Gd2O3-Y2O3:Eu. The average crystallite size was in the range of 15 to 45nm. The formation of sponge-like morphologies was confirmed by SEM-TEM images and optimized with glucose and glycine fuels. Glycine fuel was enhanced specific surface area of synthesized sample (7.11 m2/g) as compared to other organic fuel. Gd 4d, Gd 3d and Y 3d peaks were appeared as a strong XPS signal which indicated complete oxidation of Gd and Y in sample. The main emission peaks of photoluminescence spectra which are related to the electric and magnetic dipole transitions were in 5D0→7F2 (610 nm) and 5D0→7F1 (590nm) electron transitions. Glycine sample as a fuel earned the highest emission intensity of red appearance in CIE diagram by one-step combustion synthesis. Photoluminescence property europium doped Y2O3-Gd2O3 was improved using glycine as a fuel.

Development of highly luminescent PMMA films doped with Eu3+β-diketonate coordinated on ancillary ligand

In this work, [Eu(tta)3(4-picNO)2] and [Eu(dbm)3(4-picNO)] complexes were incorporated on different concentrations (x = 1, 3, 5, 10 and 15%) in PMMA polymeric matrix (4-picNO: 4-Methylpyridine N-oxide) by the solvent casting method, yielding transparent and highly luminescent polymeric films. These materials were analyzed by X-ray diffraction, scanning electron microscopy and by energy dispersive, ultraviolet–visible spectroscopy, luminescence and vacuum ultraviolet–ultraviolet spectroscopies. The luminescence spectra of doped PMMA films are in agreement with an efficient intramolecular diketonate (tta) ligand-to-europium energy transfer. Furthermore, the values of experimental intensity parameters (Ω2,4) for luminescent polymeric materials were quite similar to those ones for isolated complexes, indicating that there is a homogeneous dispersion of Eu3+ complexes in the polymeric matrix, preserving their chemical and structural features. These behavior were also observed from the CIE diagram that show great similarity between the (x,y) coordinates for the doped PMMA samples compared to the isolated β-diketonate complexes with a reddish color tuning. The photostability investigation of the doped PMMA polymeric films and Eu3+ complexes has been also reported.

Novel ratiometric optical thermometry based on dual luminescent centers from europium doped LiCa3MgV3O12 phosphor

Abstract In this paper, an optical thermometry strategy based on dual emission centers involving rare earth ions and self-activated host luminescence has been proposed, which can be used to design self-referencing optical thermometer with high temperature sensitivity and signal discriminability. Herein, we prepared non-rare-earth self-activated and rare-earth activated LiCa3MgV3O12 (LCMV) phosphors by a conventional high-temperature solid-state reaction method. Their structure, luminescence as well as temperature sensing property have been systematically investigated. In this sample, the emissions of Eu3+ ions and [VO4]3− group have been simultaneously monitored under 335 nm UV light excitation. The FIR of Eu3+ to [VO4]3- shows great temperature sensing property in temperature range from 303 K–523 K,owing to the energy transfer and thermal quenching behavior. The measured maximum absolute and relative temperature sensitivity of this phosphor are 0.011 K−1 and 1.689%K−1, which is remarkably higher than most of luminescent materials reported previously. Meanwhile, the emission peaks of [VO4]3- (475 nm) and Eu3+ (610 nm) provide a good signal discriminability for temperature detection. What's more, the emitting color in the temperature-dependent CIE diagram can highly be influenced by the external temperature and the color coordinate is verified from (0.257, 0.332) to (0.503, 0.342), which can be fitted well with the linear equation. All results indicate that the obtained phosphors not only can be promising materials for optical temperature sensors, but can be used as a color-temperature indicator.

Optical and luminescence characteristics of europium doped barium lithium fluoroborate glasses

This is a report on the synthesis and spectroscopic study of europium doped barium lithium fluoroborate glasses (Eu3+:BLFB) by conventional melt quenching technique and their structural and luminescence characteristics. The X-Ray diffraction result confirms the amorphous nature of the glasses. The Judd-Ofelt parameters (Ω2, Ω4, Ω6) were calculated from the emission spectra and the trends in the intensity parameters are found to be Ω2 > Ω4 > Ω6. The JO parameters were used to predict the radiative properties like transition probability, branching ratio, radiative lifetime and stimulated emission cross section for all the emission levels of europium (Eu3+) ions. Phonon energy (1228 cm−1) have been calculated from the phonon side band spectra. From the emission spectra, fluorescence intensity ratio (R), color chromaticity values were calculated and x, y parameters which indicates the emission of red color, as observed in the in the CIE diagram. The nature of decay profiles of 5D0 state of Eu3+ in all glasses were measured and were compared with the calculated lifetimes.

Vanadium pentoxide nanorods in latent finger print detection

Nanostructures contribute vital applications for surface-based science including latent fingerprints (LFPs) detection and reconstruction. Fingerprints are unique to an individual, matching the finger prints help to identify culprits. Vanadium Pentoxide (V2O5) nanorods were synthesized via hydrothermal method using pomegranate peel extract as fuel, towards their use in fingerprint development. PXRD patterns confirmed the formation of orthorhombic V2O5 crystal structure. Raman vibration modes at 144 cm−1 and 994 cm−1 signifies the characteristic orthorhombic V2O5 structural formation, FTIR spectra shows vibration bands of V2O5, UV–vis spectroscopy shows an intrinsic absorption band at ∼418 nm corresponding to electron transitions (O2p → V3d). The energy band gap (Eg) estimated from absorption spectrum was found to be ∼2.35 eV. Formation of nanorods was observed from SEM micrographs and particle size was found to be 30 nm from TEM images. Photoluminescence emission studies were performed and yellow –orange (brown) emission was observed from CIE diagram. The characteristic brown/Yellow-orange color of V2O5 nanorods supports tracing of LFPs on many kind of surfaces in visible light which eliminates the need for illuminating source. Hence, V2O5 nanorods find potential application in Forensic sciences.

Sm3+ doped tetragonal lanthanum molybdate: A novel host sensitized reddish orange emitting nanophosphor

Abstract A series of trivalent samarium doped lanthanum molybdate nanophosphors were prepared by co-precipitation route. The formation of highly crystalline tetragonal nanocrystals with space group I41/a is identified from powder X-ray diffractogram. The morphology and the oriented attachment mediated growth mechanism of the nanocrystals were recognized from TEM analysis. The strong and broad charge transfer band in the near ultra violet region favours excellent excitation of the nanophosphors and the energy transfer from host matrix to Sm3+ ions is established on account of the characteristic emissions of trivalent samarium ions upon host sensitization. The Judd-Ofelt (JO) theoretical analysis was carried out to have an insight into the spectroscopic characteristics of La2-xSmx(MoO4)3 nanophosphors. The relatively higher value of Ω2 predicts more asymmetric environment of Sm3+ sites in the host lattice, favouring the dominance of electric dipole transitions and the various radiative parameters are evaluated. In spite of the excitation channel, the 4G5/2 → 6H9/2 transition of Sm3+ observed at 645 nm is the most prominent emission transition. The maximum emission intensity is observed for La1.98Sm0.02(MoO4)3 nanophosphors and as the doping concentration exceeds this limit, there will be fall in emission intensity due to concentration quenching effect. A detailed investigation on the decay behaviour of host sensitized and direct excited emission of samarium ions was conducted and the average lifetime values are calculated. The CIE chromaticity co-ordinates calculated for different excitation routes fall in the reddish orange region of CIE diagram and the same for La1.98Sm0.02(MoO4)3 nanophosphors are found to be (0.601, 0.394) with a colour purity of 97.21% which disclosed the relevance of La2−xSmx (MoO4)3 as a potential red phosphor material.

Sm3+ doped calcium orthovanadate Ca3(VO4)2 - A spectral study.

Sm3+-doped vanadate-based phosphors, Ca3-x (VO4)2:Smx(x = 0.005 ≤ x ≤ 0.095), were synthesized by the citrate-based sol-gel method. The samples were characterized with XRD, SEM, diffuse reflectance and photoluminescence spectroscopy, aiming at the development of phosphor-converted wLED applications. Using diffuse reflectance spectra and the Kubelka-Munk function, the band gap energy was calculated to be 3.28 eV for the Ca2.95(VO4)2:Sm0.05 phosphor. Observation of the photoluminescence excitation spectra revealed a broadband excitation from the distorted VO4 tetrahedron and a few narrow peaks from the 4f-4f intra-configuration transitions of the Sm3+ ions. Upon 404 nm excitation, 4G5/2 → 6H5/2 (564 nm), 4G5/2 → 6H7/2 (601 nm), 4G5/2 → 6H9/2 (648 nm) and 4G5/2 → 6H11/2 (701 nm) transitions were observed. The optimum Sm3+ concentration for the studied phosphor is 0.05 mol, and the estimated critical distance between Sm3+ ions (Rc) is 19.1 Å. The observed quenching of Sm3+ emission is attributed to the dipole-dipole interactions. The possible cross-relaxation process between neighboring Sm3+ ions was discussed in detail. The CIE coordinates were calculated for all the samples, and they set on the orange region of CIE diagram. In addition, pure orange color emission was observed under 365 nm UV lamp. The results suggest that the Ca3(VO4)2:Sm3+ phosphor could be a good candidate for the orange emitting component for wLED applications.

Physical and luminescence properties of samarium doped oxide and oxyfluoride phosphate glasses

Abstract The research work emphasizes on physical and luminescence properties of oxide and oxyfluoride phosphate glasses and discusses the energy transfer between Gd3+ and Sm3+ ions. Lithium gadolinium oxide and oxy-fluoride phosphate glasses doped with Sm3+ ions were prepared by conventional melt quenching technique. Subsequently the physical and luminescence properties were investigated systematically to understand their behavior. The density of the prepared glass samples show high in oxide glasses as compared to oxy-fluoride glasses, and the density of both glass samples increase with increase in the Sm2O3 concentrations. In total, ten signature Sm3+ ion peaks were observed in the UV-Vis-NIR absorption spectra. In photoluminescence spectra the oxy-fluoride glass samples show higher excitation and emissions intensity than oxide glasses. The emission intensity increases up to 1mol% concentration of Sm3+ ions and then decreases due to non-radiative energy transfers. The same is observed in case of radioluminescence emission spectra. The calculated J-O intensity parameters show Ω2 > Ω4 > Ω6 trend. From Judd-Ofelt analysis, these glasses exhibit high potential for using as laser host medium. The life time recorded at the excitation and emission wavelength 401 nm and 598 nm respectively and it is observed that the life time decreases with increase in the Sm3+ ions concentration. The CIE coordinates positioned in the orange region of CIE diagram. The properties evaluated in the present work indicate that these glasses can be a good candidate of orange LEDs applications.

Emission color tuning and phase transition determination based on high-pressure up-conversion luminescence in YVO4: Yb3+, Er3+ nanoparticles

Compression of up-converting (UC) YVO4 nanocrystals doped with Yb3+ and Er3+ ions leads to the luminescence color tuning, which can be used for the determination of pressure-induced zircon-to-scheelite phase transition. Spherical (≈20 nm), tetragonal YVO4: Yb3+-Er3+ UC nanoparticles (NPs) were synthesized by the hydrothermal method. The high-pressure spectroscopic analysis (up to ≈11 GPa) of the material was carried out in a diamond anvil cell (DAC), in a compression-decompression run. With the increasing pressure values, the intensity of UC emission (λex= 975 nm) decreased along with shifts of the band centroids. The maximum shifts was ≈ 0.39 nm/GPa, for the 4F9/2→4I15/2 transition. Broadening of the bands and overlapping of the split Stark sub-levels were also observed. The sudden and huge change in the band ratios, and deviations from the linear shift tendency of chromaticity coordinates in the CIE diagram around ≈ 8 GPa, clearly shows the influence of phase transition on the luminescence properties of the material, under high pressure conditions.

Luminescence characteristics of Sm3+-doped lithium barium gadolinium silicate glasses for Orange LED's.

Traditional melt-quenching technique is adopted for synthesis of Sm2O3 doped lithium barium gadolinium silicate (LBGS: Li2O-BaO-Gd2O3-SiO2) glasses. These glass samples are characterized by different spectroscopic techniques under ambient conditions. Density and molar volume of the present LBGS glass samples increase with increasing Sm3+ ion-concentration. JO intensity parameters Ωλ (where λ = 2, 4 and 6) are evaluated by using Judd-Ofelt theory and Ω4 > Ω2 > Ω6 trend is observed. Furthermore, these parameters are used to evaluate radiative properties like radiative transition probability, branching ratio, radiative lifetime and stimulated emission cross-section for state 4G5/2 of Sm3+ ion. The measured color coordinates for the title glass fall within orange region of CIE diagram. For the present LBGS glasses, the correlated color temperature values are less than warm. The lifetime for the 4G5/2 decreases from 2.468 to 0.566 ms when concentration increases from 0.1 to 2.0 mol% of Sm3+ ions. The analysis of non-exponential behavior of the decay profile through Inokuti-Hirayama model for S = 6 indicates that the energy transfer between Sm3+ ions is due to dipole-dipole interactions. Further energy transfer parameters (Q), critical distance (Ro, Å) and donor-acceptor interaction parameters (CDA x 10-40 cm6/s) of Sm3+ ions doped LBGS glasses were evaluated and compared to other glasses. From the evaluated results it is suggested that the present novelty of the work emphasizes on new matrix LBGS doped with Sm3+ ions showing increasing energy transfer rate with increasing in concentration of Sm2O3 content indicating these glasses are potential candidate for orange-light emitting device applications.

Dy3+ doped calcium boroaluminate glasses and Blue Led for smart white light generation

Dy2O3 doped calcium boroaluminate (CaBAl) glasses (50) B2O3-(25-x) CaO-(15) Al2O3-(10) CaF2-(xDy2O3) (x = 0.0, 0.5, 1, 2, 3, and 5 wt%) were prepared by using the conventional melt-quenching technique and characterized through XRD, FTIR, refractive index, volumetric density, absorption, excitation, photoluminescence and lifetime measurements. The amorphous nature of the CaBAl glasses was confirmed through XRD measurements. FTIR analysis allowed identifying stretching and bending vibrations of different borate groups. Absorption spectra presented characteristic peaks of Dy3+, corresponding to transitions from the 6H15/2 ground state to the excited energy levels. Oscillator strengths and Judd–Ofelt intensity parameters (Ωt = 2, 4 and 6) were calculated from the absorption spectra. The photoluminescence spectra of the Dy3+ doped CaBAl glasses, under 405 nm excitation, exhibited two intense emission bands corresponding to the 4F9/2 → 6H15/2 (blue) and 4F9/2 → 6H13/2 (yellow) transitions. The intensity of Dy3+ emission spectra increased with Dy2O3 content from 0.5 wt% to 3 wt% and concentration quenching was observed for concentrations higher than 3 wt%. The yellow/blue (Y/B) ratio was investigated as a function of Dy2O3 content. The simulation of a combination of a Blue LED (BL) emission with the sample emission was also studied in the CIE diagram, in order to evaluate the possibility of smart white light generation. Photoluminescence decay curves, fitted by Inokuti-Hirayama model (S = 6), indicates a dipole-dipole interaction between donor and acceptor Dy3+ ions in the glass. All results suggest that the investigated CaBAl:Dy3+ glasses are candidates for W-LEDs application and smart lighting.