Judd-Ofelt Calculations Research Articles

Influence of crystal field inhomogeneities on the spontaneous and laser tuning emission of a Nd3+-doped Li2O-BaO-Al2O3-P2O5 glass

The present work focuses on the spectroscopic and laser properties of Nd3+ in a Li2O-BaO-Al2O3-P2O5 aluminophosphate glass which includes Judd-Ofelt calculation, stimulated emission cross-section of the 4F3/2→4I11/2 emission laser transition, lifetime of the 4F3/2 state and quantum efficiency. Site-selective laser spectroscopy and stimulated emission under selective excitation has been performed to determine the crystal field inhomogeneity at the Nd3+ site together with its broadening effect on the spontaneous and laser emissions. However, a much narrowed laser emission has been achieved by using an intracavity tilting plate which acts as a tunable optical filter to adjust the laser wavelength.

Comprehensive investigation of Y2Si2O7:Eu3+ nanophosphors for w-LEDs: Structural, Judd-Ofelt calculation and photoluminescent characteristic with high color purity and thermal stability

In recent decades, numerous red phosphors have been designed and developed. Nevertheless, many of them are unsatisfactory due to their low brightness and poor thermal stability. Look at these shortcomings; present study reports on Eu3+ doped Y2Si2O7 (YPS) phosphors, synthesized through low temperature based urea assisted gel-combustion method. Comprehensive investigations were conducted on phase purity, luminous characteristics, energy transfer mechanism, quantum efficacy, morphology, elemental makeup, band gap and thermal stability. XRD analysis was employed to verify the preparation of Y2Si2O7 matrix with triclinic structure (P-1 space group). Morphology and elemental investigations of the fabricated materials was evaluated via TEM and EDX techniques respectively. Under the illumination at 393 nm, the most strong emission band is shown in PL spectra at 613 nm (electric dipole 5D0→7F2 transition). Additionally, the dipole-quadrupole (d-q) interaction was found to be the predominant route of energy transfer among nearby Eu3+ ions and it was concluded that 3 mol % was the optimal doping concentration of Eu3+ ions. The Judd-Ofelt (J-O) theory was used for current phosphors in order to establish their Ω2 and Ω4 with other radiative parameters. The assessment of thermal stability yielded highly promising results with activation energy of 0.241 eV. Present research indicates that Y2Si2O7:Eu3+ is a promising candidate of red emitting phosphor for white light-emitting diodes.

Optimizing hexafluoro-2,4-pentanedione based Eu(III) complexes: A comprehensive study on the synthesis, spectroscopic characterization with Judd-Ofelt calculation

Utilizing Europium(III), compounds having eight-coordination geometry of the type [Eu(hfpd)3L2] and [Eu(hfpd)3Lʹ] were synthesized [hfpd = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione, L = tri-octyl-phosphine oxide (TOPO) and Lʹ = 1,10-phenanthroline (phen), Neocuproine (neoc) and bathocuproine (bathoc)] and characterized through elemental, FTIR, CV and Proton-NMR techniques. Photoluminescent studies and quantum yield helped to understand the role of coordination environment and ligands on the emission intensity. Luminescence decay curves served as the basis for calculating the excited-state lifetimes of the synthesized complexes. JO parameters (Ω2, Ω4) and asymmetry ratio were also evaluated to study the coordination environment around the central metal ion. Solid-state complexes exhibited an intense, monochromatic bright red emission, as characterized by its Commission International de l’Eclairage (CIE) color coordinates. Owing to red luminescence and semi-conducting properties, these Eu(III) complexes can be employed as red-emitting material for fabricating lighting devices.

Photophysical analysis and Judd–Ofelt calculation of Eu (III) complexes: Influence of various neutral ligands on luminescent properties

This article presents the preparation and characterization of a series of four tris-β-diketonate Eu(III) complexes with formulation of [Eu(tfaa)3(L)n], tfaa denotes the 1,1,1-trifluoroacetylacetone, L to monodentate or bidentate neutral ligand with nitrogen and oxygen as donor atom and n can be 1 and 2. The characterization of synthesized complexes was done using infrared spectroscopy, thermo-gravimetric analysis and proton NMR spectroscopy. UV–vis absorption, photoluminescence as well as time-resolved luminescence spectroscopies were also employed to examine the spectroscopic features of ternary complexes. The proton NMR and IR spectral information has suggested the bonding of organic moieties to the Eu(III) ion. The chemical shift obtained for the protons of primary and secondary moieties are shifted in an opposite direction. The band gap values (optical and electronic) suggest the semiconducting nature of prepared europium complexes. The trivalent ion centered emission is shown by all the prepared complexes on excitation under UV-light. The hypersensitive peak situated at about 612 nm responsible for red emission is corresponding to 5D0→7F2 transition and found to be sensitive to the chelating environment present at around emissive ion. Red emanating europium materials have acquired significant utilization in OLEDs, flat panel displays and solid state electronics.

Optical transition tuning of Er3+ in continuous tungsto-molybdate solid solution NaY(MoxW1-xO4)2 phosphors

Nowadays, the application scenarios of rare earth doped luminescent materials tend to be refined and complicated. The optical properties of rare earth doped materials are difficult to precisely control via the traditional design and synthesis methods, namely, changing doping concentration or preparative conditions. The aim of this study is to tune the optical transition properties of Er3+ in tungsto-molybdate NaY(MoxW1-xO4)2 (x = 0, 0.01, 0.1, 0.3, 0.5, 0.7, 0.9, 0.99 and 1.0) phosphors by changing the host matrix. The Er3+ doped continuous tungsto-molybdate solid solution NaY(MoxW1-xO4)2 phosphors were prepared via a solid state reaction technique at optimized calcination temperatures. The refractive indexes of the obtained solid solution samples were confirmed according to different models and compared. Subsequently, the optical transition intensity parameters, radiative transition rates and intrinsic radiative lifetimes of Er3+ in these solid solution phosphors were calculated in the framework of Judd-Ofelt theory. It was confirmed that the optical transition properties of Er3+ can be greatly tuned by the solid solution composition, and the tuning effects for different transitions are different. To validate the reliability of the Judd-Ofelt calculations, the temperature-dependent emission spectra of two green emissions of Er3+ for different solid solution samples were studied. It was found that the radiative transition rate ratios between two green emissions derived from theoretical calculations and experimental measurements are in reasonable agreement, thus proving that the optical transition calculations are reliable and the optical transition properties of Er3+ in the tungsto-molybdates can be tuned in a large range. This work reminds us of a new route for developing novel luminescence materials based on practical demands.

Red-emitting Eu3+ activated LaSr2AlO5 phosphor for wLEDs: Crystal structure, photoluminescence, thermal stability, Judd-Ofelt calculation and band-gap analyses

Red-emitting La1-xSr2AlO5:xEu3+ (x = 0.01–0.06) phosphors have been synthesized via gel combustion (GC) approach and their structure and luminescent characteristics were analyzed in detail. The tetragonal crystal structure (I4/mcm space group) of all generated La1-xSr2AlO5:xEu3+ (x = 0.01–0.06) phosphors have been established by X-ray diffraction and rietveld analysis. The shape and size of the phosphor has been examined using transmission electron microscopy (TEM) and the estimated crystallite size was found to be 32–65 nm. Energy Dispersive X-ray (EDX) analysis confirmed the chemical composition of the synthesized materials. The diffuse reflectance spectra (DRS) were used to compute the band gap energies (Eg) of the samples which emerged to be in region of 5.373–6.009 eV. The Eu3+ activated LaSr2AlO5 phosphors produce red emissions at 579, 592, 614, 656 and 708 nm, when excited at 395 nm. These emission bands are caused by 5D0→7FJ (J = 0, 1, 2, 3, 4) electronic transitions of Eu3+ ion. The Judd-Ofelt theory further supports the performance of LaSr2AlO5:Eu3+ phosphors as a red emitting substance with high branching ratio corresponding to 5D0→7F2 transition from Eu3+ center present in the low symmetry site. Computed chromaticity coordinates (x, y) indicate a high degree of color purity in the phosphors, providing additional evidence for the presence of red emission. Temperature dependent emission (PL) spectra revealed good thermal stability of the synthesized nanophosphors with activation energy (Ea) of 0.1384 eV.

Achieving narrow bandwidth and high stimulated cross-section in Nd3+-doped LiCaB glasses for near infra-red laser amplifiers

The aim of this research is to examine the effects of Nd3+ ions on the spectroscopic characteristics of different concentrations of lithium-calcium-borate glasses and improve the emission cross section alongside bandwidth. The prepared glasses were produced with the melt-quenching technique and were thoroughly analyzed to determine their usefulness as laser amplifiers. Various studies were conducted, including X-ray diffraction (XRD), solid-state nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), absorption and emission measurements, and time decay curve measurements. The structural analysis using XRD and NMR techniques revealed that the glasses were amorphous and that non-bridging oxygen was present. Moreover, it was discovered that the glass-forming tendency and glass stability of these glasses improved with the concentration of Nd3+ ions. The glasses' absorption spectra display 10 transition states in UV and visible regions. Among all the prepared glasses, the lithium-calcium-borate glass doped with 0.5 mol % Nd3+ ions stand out with a stimulated emission cross-section value of 3.40 × 10−20 cm2 and a narrow bandwidth of 33 nm, making it an ideal lasing amplifier medium due to the 4F3/2 → 4I11/2 (1060 nm) transition. Theoretical Judd-Ofelt calculations were conducted to evaluate various parameters, including oscillatory strength, radiative parameters, radiative lifetime, gain bandwidth, figure-of-merit, and saturation current, for all transitions in the near-infrared region, to support the experimental investigations and offer a detailed discussion of these parameters.

Study of structural, luminescence and Judd-Ofelt calculations for Ce3+ doped ZnS phosphors for display applications

This paper discusses the luminescence properties of novel Zn(1-x)S: xCe3+ (x = 0, 0.01, 0.02, 0.03, 0.1, 0.2 and 0.3) prepared via conventional solid-state reaction method at low temperature. The XRD results revealed that all synthesized phosphors have hexagonal structure. The strain was calculated using size-strain plot (SSP) method. The FTIR study identifies the various vibrational modes present in the synthesized phosphors. The structural and luminescence characteristics of the prepared samples were enhanced by Ce3+ substitution. The optical band gap energies were found to be decreasing with Ce3+ substitution. The optimal Ce3+ content for superior blue emission is found to be x = 10 mol %. The blue emission supports the incorporation of Ce3+ ions within the ZnS lattice, which is again confirmed by Ω2, Judd-Ofelt intensity parameter. The high value of Ω2 indicates the symmetry of site occupies of Ce3+ ions are lower. The obtained critical distance of energy transfer between Ce3+ ions is calculated to be 6.3095 Å, which implies that the exchange interaction mechanism is a multipolar exchange. The high efficiency, branching ratio, stimulated cross section and the optical parameters indicate that the prepared phosphor materials have efficient blue light emission for display applications.

Optical transition and near-infrared upconversion luminescence properties of YNbO4: Er3+, Yb3+ phosphors

Optical transition and near-infrared upconversion luminescence properties of Er3+ single-doped and Er3+, Yb3+ co-doped YNbO4 phosphors are reported. Based on the framework of Judd-Ofelt theory and modified Judd-Ofelt calculation method, the optical transition properties of Er3+ and Yb3+ ions in YNbO4: Er3+, Yb3+ sample were studied, respectively. The calculated results showed that the absorption cross-section of Er3+ ion at ∼1550 nm is larger than that at ∼980 nm in YNbO4: Er3+ phosphor. And, the absorption cross-section of 2F7/2 → 2F5/2 transition of Yb3+ in YNbO4: 15.0 mol% Er3+, 15.0 mol% Yb3+ sample was calculated to be 138.70 × 10−20 cm2. According to the emission cross section of Er3+ (4I11/2 → 4I15/2) and the absorption cross section of Yb3+ (2F7/2 → 2F5/2), the energy transfer rates from Er3+ to Yb3+ were quantitatively analyzed via the Föster-Dexter model. Furthermore, 1550 nm was selected as the excitation wavelength, the near-infrared upconversion emission spectra of YNbO4: Er3+, Yb3+ samples were measured. It was found that the sample has strong emission at ∼980 nm and the emission intensity was still enhanced with the incorporation of Yb3+.

Enhanced up- and down-conversion luminescence from Dy3+-Sm3+ co-doped B2O3-SrCO3-TeO2-Al2O3-MgO glass hosts: effects of CuO nanoparticles embedment

In the up-conversion nonlinear optical process, the absorption of lower energy photons causes the emission of photons at higher energy due to various mechanisms like sequential optical excitation, energy transfer, and nonlinear light-matter interaction processes. Improving the up- and down-conversion luminescence of different lanthanide-doped glasses via metallic nanoparticle embedment remains challenging. There has been no clear understanding of how copper oxide nanoparticles (CuONps) affect the spectroscopic properties of Dysprosium-Samarium ions (Dy3+-Sm3+)-co-doped glasses. Thus, new CuONps-infused strontium-telluro-aluminum-magnesium-borate glass samples were prepared using the standard melt-quenching technique with Dy3+-Sm3+ co-doping. X-ray diffraction (XRD) analysis confirmed the samples' glassy nature. High-resolution transmission electron microscopy (HRTEM) provided the orientation and size distribution of the embedded nanoparticles in the glass hosts. The downconversion luminescence emission (at 350 nm excitation) corresponds to 4F9/2 → 6H15/2, 4F9/2 → 6H13/2, and 4F9/2 → 6H11/2 transitions in Dy3+. Judd-Ofelt calculations for the CuONps embedded sample showed significant radiative properties. A branching ratio of 79.6% was attained. The upconversion luminescence emission (at 896 nm excitation) bands corresponded to 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions for the Dy3+-doped glasses. In addition, an intense peak due to the 4G5/2 → 6H7/2 transition in Sm3+ was observed in the co-doped glasses. It was determined that the increased up-conversion luminescence was related to localized surface plasmon resonance, energy transfer, and local field enhancements caused by CuONps inclusion. It was confirmed that excited state absorption and energy transfer mechanisms were involved in the up-conversion luminescence. Synthesized glasses may be helpful for upconversion displays, optical data storage, and solid-state lasers.

The 1.5 μm spectroscopic properties of Yb,Er:GSAG crystal: A promising 1.5 μm laser gain medium

The 1.5 μm lasers exhibit excellent eye safety characteristics that make them crucial for laser ranging, radar and optical communication. In this work, the 1.5 μm spectroscopic properties of a mixed garnet crystal, Yb,Er:GSAG, were investigated. The strongest absorption at 940 nm overlaps well with the currently mature InGaAs laser diodes. Under 940 nm excitation, a strong emission band with peak wavelength at 1534 nm was detected. The Judd-Ofelt calculation was performed based on the measured absorption spectrum, and the three intensity parameters Ωt (t = 2,4,6) were fitted as 0.974 × 10−20 cm2, 0.477 × 10−20 cm2 and 0.352 × 10−20 cm2, respectively. The absorption cross-section at 940 nm and emission cross-section at 1534 nm were calculated as 0.59 and 0.81 × 10−20 cm−1, respectively. Lastly, a positive gain cross-section can be achieved at 1534 nm when the population inversion ratio β is only higher than 0.2. The results imply that this crystal is a promising 1.5 μm near infrared laser gain medium.

Simultaneous enhancement of quantum cutting luminescence in Er-doped NaBaPO4 phosphors by crystal field control and plasmonic modulation

It is of great significance to enhance the quantum-cutting (QC) luminescence for practical applications due to the narrow absorption cross-section and low luminescence efficiency of rare earth ions. In this work, NaBaPO4:Er3+ phosphors doped with Li+ were synthesized through a solid-state reaction. The QC luminescence of NaBaPO4:Er3+ phosphor was enhanced 5.71 times by doping Li+. XRD patterns and Judd-Ofelt calculations demonstrated the crystal field distortion when introduced Li+, which would increase the transition probability of Er3+. Furthermore, NaBaPO4:Er3+, Li+ phosphors were decorated with silver nanoparticles (Ag NPs). The effect of Ag NPs on QC luminescence was studied, and the results showed that QC luminescence was further enhanced up to 1.95 times by Ag NPs. FDTD simulations revealed that Ag NPs generated substantial surface plasmons, which would boost the excitation rate of Er3+. Our studies would provide a useful strategy to enhance QC luminescence, which has potential application in germanium-based solar cells.

Optical transition properties, internal quantum efficiencies, and temperature sensing of Er3+ doped BaGd2O4 phosphor with low maximum phonon energy

AbstractThe hosts with low maximum phonon energy (MPE) are preferred since the nonradiative consumption of the luminescence centers in them are low. Among the low MPE hosts, the oxide ones are more favored owing to their excellent stability and easy synthesis. In this work, the optical and spectroscopic properties of BaGd2O4:Er3+ phosphor were studied. The MPE of BaGd2O4 host was observed from Eu3+ phonon sideband (PSB) spectrum and Raman spectrum to be 477 cm−1 which does not second to the fluoride hosts. The refractive index, which is indispensable for Judd–Ofelt calculation, was confirmed from the both approaches of the Eu3+‐probe and the band gap energy, and the similar refractive indices were confirmed, therefore the average refractive index 2.01 was used in the Judd–Ofelt calculation. The Judd–Ofelt parameters of Er3+ in BaGd2O4 host was confirmed to be = 7.91 × 10−21 cm2, = 2.36 × 10−21 cm2, and = 9.00 × 10−22 cm2. Furthermore, the internal quantum efficiencies for 4F9/2 and 4IJ (J = 9/2, 11/2, and 13/2) levels were determined. Finally, the optical temperature sensing properties were studied in detail, and the temperature calibration curve was experimentally derived, meanwhile the maximum absolute sensitivity was confirmed to be 0.0028 K−1.

Dehydroxylation processing and lasing properties of a Nd alumino-phosphate glass

In this work, we have studied the preparation and properties of an alumino-phosphate glass with composition 13Na2O-13K2O-16BaO-4Al2O3-54P2O5 (mol%). The first part of the work deals with the study of the processing conditions of the dehydroxylation of the phosphate glass, which was performed by remelting under N2 flow using graphite crucibles. Glass samples from 5 to 50 g and Nd2O3 doped were submitted to dehydroxylation and the influence of temperature, time, mass of glass and viscosity were correlated with the content of water in the glasses through the coefficient of absorption of OH ions. The network structure of the glasses was also determined by means of 31P and 27Al 1D/2D nuclear magnetic resonance and the local environment of Nd3+ ions was probed by electron paramagnetic resonance. The optimized conditions of processing were then used to obtain a dehydroxylated glass with a 2.5 wt% Nd2O3 whose spectroscopic and laser emission properties were studied. The spectroscopic properties of Nd3+ ions which include, Judd-Ofelt calculation, stimulated emission cross-section of the laser transition, lifetime, and quantum efficiency are presented. Site-selective laser spectroscopy and stimulated emission obtained under selective wavelength pumping along the 4I9/2→4F5/2 absorption band were performed to determine the distribution of crystal field in which the rare earth is located, together with its influence in the pump wavelength dependence of the spontaneous and laser emissions of Nd3+ in this glass matrix.

Growth, Optical, and Spectroscopic Properties of Pure and Nd3+-Doped GdSr3(PO4)3 Crystals with Disordered Structure.

Disordered crystals have attracted immense attention for the generation of ultrashort laser pulses due to their good thermomechanical characteristics and wide emission bandwidths. In this work, a Gd-based orthophosphate crystal, GdSr3(PO4)3, (GSP), and a Nd3+-doped GdSr3(PO4)3 crystal, (Nd:GSP), were obtained by the Czochralski method. The crystal structure, optical properties, electronic band structure, laser damage threshold, and hardness of the GSP crystal were comprehensively investigated. It exhibited a disordered structure due to the random distribution of Sr and Gd atoms in the same Wyckoff site, which caused inhomogeneous spectral broadening. Additionally, it exhibited a short UV absorption cutoff edge (<200 nm), a large band gap (5.81 eV), and a high laser damage threshold (∼1850 MW/cm2). The spectral properties and Judd-Ofelt calculations of the Nd:GSP crystals were analyzed. A wide absorption band at 803 nm, with a full width at half-maximum value of 20 nm, makes the Nd:GSP crystal suitable for the efficient pumping of AlGaAs laser diodes. Sub-100-fs pulses could be supported by its 25 nm emission bandwidth. Hence, the GSP crystal could be a promising disordered crystal laser matrix.

Re-study of Judd-Ofelt spectroscopic properties of Er3+-doped Gd3(Al, Ga)5O12 single crystal

A previous paper [J. Lumin. 177 (2016) 219] has studied Judd-Ofelt spectroscopic properties of Er3+ (0.5 at%)-doped Gd3(Al, Ga)5O12 garnet single-crystal, and reported the Judd-Ofelt intensity parameters Ω2 = 1.47 × 10−20 cm2, Ω4 = 1.38 × 10−20 cm2 and Ω6 = 1.19 × 10−20 cm2. We have performed a re-study on the Judd-Ofelt spectroscopic properties of a similar garnet single-crystal Er3+(20 at%)-doped Gd3(Al0.4Ga0.6)5O12, and obtained quite different values of Judd-Ofelt intensity parameters Ω2 = (0.34 ± 0.11) × 10−20 cm2, Ω4 = (0.48 ± 0.16) × 10−20 cm2 and Ω6 = (1.05 ± 0.17) × 10−20 cm2. The quite different Ωt values given by two studies are mainly due to remarkably different absorption characteristics of Er3+ in the crystals employed in two studies, and factors that lead to quite different absorption characteristics are discussed. Another reason is that the hypersensitive transition at 380 nm was excluded from the Judd-Ofelt calculation in that paper, resulting in deviation of their result. Instead, all of the Er3+ absorption bands were included in our calculation, allowing to obtain more accurate Ωt values. Quite different Ωt values lead to considerable differences of relevant spectroscopic parameters, such as radiative rates and lifetimes of typical Er3+ emissions, for which the difference from each other is as much as three times. In addition, visible, near-infrared and mid-infrared fluorescence spectra and lifetimes of Er3+ in the studied crystal were measured, and the emission characteristics are discussed.

Photoluminescence properties of y at.% Eu3+-doped Gd(NbxP1-x)O4: A color-tunable orange-red phosphor

In this work, a simple method to prepare orange-red phosphor is introduced. A series of y at.% Eu3+-doped Gd(NbxP1-x)O4 (x = 0%, 1%, 2%, 3%, 4%, 5%, 6%, 10% and y = 5%, 7%, 9%, 11%, 13%, 14%, 15%) phosphors were prepared through solid reaction technique. The structure and optical properties of the phosphors were characterized using measurements of X-ray powder diffraction, photoluminescence excitation, photoluminescence and decay curves. The X-ray diffraction results revealed that the obtained phosphors possessed the same pure monoclinic phase as GdPO4 until the doping concentration of Nb5+ reached a maximum value of 5 at.%. With the high sensitivity of the 5D0→7F2 transition to the symmetry of the crystal field, the relative intensity of the two emission peaks at 596 and 615 nm could be continuously adjusted by changing the Nb5+ concentration. Moreover, Judd–Ofelt calculations performed on samples doped with different Eu3+ ions concentrations showed their promise as color-tunable orange-red phosphors.

Effects of Sc3+ ions on local crystal structure and up-conversion luminescence of layered perovskite NaYTiO4: Yb3+/Er3+

This work focused on influences of Sc3+ dopants on local site symmetry and ligand field of Er3+ activators as well as its up-conversion luminescence performances sensitized by Yb3+ ions in NYTiO4 (NYT). The structure analysis and Judd-Ofelt calculation confirmed that doping Sc3+ ions could lower site symmetry as well changed the ligand field around Er3+ ions. The introduction of Sc3+ ions induced variations of crystal lattices, regulated distances between Er3+ions and Er3+ or Yb3+ ions, and thus influenced the up-conversion luminescence properties. Besides, time-resolved decay curves figured out the great enhancement of lifetime and luminescence quantum efficiency for both green and red emissions due to Sc3+ dopants. For optical temperature sensitivity, thermally coupled levels (TCLs) for blue emission 4F5/2/4F7/2→4I15/2 was studied for the first time. Besides, TCLs for violet emission 4G11/2/2H9/2→4I15/2 as well as green emission 2H11/2/4S3/2→4I15/2 were also recorded. By tri-doping Sc3+ ions into NYT: Yb/Er, both absolute sensitivity and relative sensitivity of above three TCLs were improved with temperature uncertainty decreasing.

Triple molybdates and tungstates scheelite structures: Effect of cations on structure, band-gap and photoluminescence properties

A series of eight compounds with general composition A′AEu(MO4)3 (where A′ = Li+ and Ag+; A = Ca2+ and Sr2+ and M = Mo6+ and W6+) have been synthesized by conventional solid state reaction route. These compounds are characterized by Powder X-ray Diffraction(PXRD), Fourier Transform Infrared (FTIR) spectroscopy and Raman spectroscopy. The Rietveld refinement of PXRD patterns of the compounds is carried out to find out the structural characteristics. These experimental techniques confirm the scheelite structure of compounds. The band-gap of the compounds was measured by UV-DRS method. The band-gaps in tungstate compounds are larger than those of molybdates. The photoluminescence properties of these compounds were elucidated recording excitation, emission and lifetime spectra. The effect of cations on photoluminescence properties of these compounds was studied. The silver containing compounds are shown to have superior photoluminescence when excited by 395 nm light (f-f transition), but when excited by charge transfer band (CTB) energy, these compounds show degradation of the matrix. The reason of this contrasting effect is due to the reduction of Ag+ to Ag0. The photoluminescence properties of molybdates are better in comparison to those of tungstates due to higher covalence of Eu–O bond in molybdates, as evidenced by Judd-Ofelt calculations.

Luminescence of Neodymium Ion-Activated Magnesium Zinc Sulfophosphate Glass: Role of Titanium Nanoparticles Sensitization

Abstract A series of neodymium ion (Nd3+)-activated magnesium zinc sulfophosphate glasses sensitized with various contents of titanium nanoparticles (Ti NPs) were prepared via the melt-quenching method and characterized. The influence of Ti NPs on the optical characteristics of the glasses was determined. The XRD patterns of the as−quenched samples verified their amorphous nature. The differential thermal analyses (DTA) of the samples showed their good thermal stability against crystallization. The HRTEM image of the samples exhibited the formation of Ti3O5 NPs inside the amorphous network. The SPR bands of Ti3O5 NPs were probed at 587 nm and 730 nm. The ESR spectra of the glasses disclosed the existence of the singlet oxygen induced by the surface plasmon resonance (SPR) effect of Ti3O5 NPs. The absorption spectra of the glasses revealed twelve characteristic bands of Nd3+. The Judd-Ofelt calculations were performed to support the experimental spectroscopic results. The up−conversion (UC) photoluminescence (PL) emission spectra of the glasses revealed an intense yellow band at approximately 585 nm due to the 4G5/2 + 2G7/2 → 4I9/2 transition in Nd3+. The glass prepared with 0.4 mol% of Ti NPs displayed the highest PL intensity enhancement and maximum gain bandwidth. In short, the overall properties of the glasses were sensitive to the contents of Ti NPs. The observed improvement in the optical traits of the proposed glasses was attributed to the Ti NPs SPR-induced local field effect (LFE) in the proximity of Nd3+. Present findings could contribute to the development of the proposed glass-based solid−state laser and photonic devices.