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The photoluminescence characteristics of praseodymium (Pr 3+ ) doped zirconia/polyethylene glycol (ZrO 2 /PEG) samples were studied using optical absorption and emission spectra. The optical properties were theoretically analysed using standard and modified Judd-Ofelt (J-O) models. The oscillator strength of the observed transitions and J-O intensity parameters were calculated using these J-O models. The radiative properties such as radiative transition probability ( A T ), branching ratio ( β R ), stimulated emission cross-section ( σ e ) and gain band width ( σ e × Δ λ e f f ) for the excited states of Pr 3+ in ZrO 2 /PEG composite have been determined. The experimental branching ratios obtained from the emission spectra were compared with the theoretical values. The excitation spectra of Pr 3+ doped samples show overlapping of Pr 3+ excitation peak at 448 nm at the end of the broad excitation band of the host, indicating the charge transfer between the host and Pr 3+ ions. Luminescence decay analysis confirmed concentration quenching in the prepared samples and the lifetime values are found to be in the microsecond range. [ABSTRACT FROM AUTHOR]

A new borate solid solution series of powders, Li 6 Eu 1-x Sm x (BO 3 ) 3 (LSEBx, x = 0.35, 0.5, 0.6, 1), were synthesized by solid-state reaction, characterized and their luminescent properties were investigated. The absorption spectra indicate that absorption takes place mainly from the Sm 3+ 6 H 5/2 ground state, with a strong band at 405 nm. The photoluminescence spectra reveal that the Eu 3+ red emission intensity strongly depends on the Sm 3+ content x. Judd–Ofelt theory was applied to experimental data for the quantitative determination of phenomenological parameters Ωi (i = 2, 4, 6) Judd Ofelt parameters, radiative transition rates and emission quantum efficiency. Owing to the energy transfer from Sm 3+ to Eu 3+ the intense red light detected at 613 nm at room temperature under UV or blue light excitation, was improved by ∼35% as compared with Sm 3+ -free samples. This energy transfer was confirmed by faster decay times of Sm 3+ as energy donors. Moreover, the energy transfer between Sm 3+ and Eu 3+ is unidirectional and irreversible, implying that the energy transfer wastage between Sm 3+ and Eu 3+ is very low. Magnetic susceptibility (χ) measurements of LSEBx were carried out in the temperature range 2–320 K and are used to compare calculated and experimental energy levels. [ABSTRACT FROM AUTHOR]

In this paper, structural and optical properties of WO 2.72 thin films implanted by 150 keV Ni ions having ion fluences in the range of 1015 to 1016 ions/cm2 have been investigated. Structural investigations (Raman and XRD) suggest the formation of the crystalline monoclinic phase of pristine films. However, after ion implantation, the crystalline quality degrades as a function of ion fluences, and complete amorphization is observed at highest fluence. Further, the bandgap decreases upon ion implantation as a result of band tailing effect. Optical investigation under UV excitation delineates the existence of NUV, band-to-band transition and blue green emission bands in WO 2.72 thin films. Implantation-assisted Ni doping blueshifted the new NUV emission peaks due to the enhancement in free electron concentration in the conduction band (CB). The overall hue of the emitted light investigated using Commission International de l'Eclairage (CIE) diagram demonstrates the transition from light to deep blue region upon Ni implantation. • Structural and optical properties of WO 2.72 thin films implanted with Ni ions were studied. • Amorphous films are obtained at high Ni fluences. • Multiple radiative transitions due to intrinsic and implantation induced defects were obtained. • Implantation-assisted doping of Ni leads to the production of oxygen vacancies. • The CIE coordinates depicts the tuning of color from light blue to deep blue. [ABSTRACT FROM AUTHOR]

Sr 3−2 x Sm x Na x B 2 SiO 8 phosphors were synthesized by the solid-state reactions. X-ray diffraction, diffuse reflection, photoluminescence excitation and emission, as well as fluorescence decay measurements were utilized to investigate the structural and spectral properties of the samples. The results indicated that Sr 3−2 x Sm x Na x B 2 SiO 8 phosphors could be efficiently excited by the near-ultraviolet light to realize a novel reddish orange luminescence corresponding to the characteristic transitions 4 G 5/2 → 6 H J (J = 5/2, 7/2, 9/2, 11/2) of Sm 3+ ions, with a maximum intensity at 600 nm. Based on the theoretical calculation, the dipole–dipole interaction was dominantly involved concentration quenching of Sm 3+ in the phosphors, and the critical transfer distance ( R c ) was determined to be 13.59 Å. Furthermore, Judd-Ofelt analysis was applied to evaluate three phenomenological Judd-Ofelt intensity parameters ( Ω λ , λ = 2, 4, 6), and in turn radiative properties such as radiative transition probabilities ( A R ), radiative lifetimes ( τ R ) and fluorescence branching ratios ( β R ) for the excited 4 G 5/2 luminescent level of Sm 3+ ions were determined. Upon 402 nm excitation, the composition-optimized Sr 2.90 Sm 0.05 Na 0.05 B 2 SiO 8 exhibited the preferable photoluminescence intensity and CIE coordinates of (0.534, 0.448). These results suggest that the Sm 3+ -doped Sr 3 B 2 SiO 8 phosphors are competitive as the reddish orange-emitting phosphor-converted materials for application in near-ultraviolet-pumped LEDs. [ABSTRACT FROM AUTHOR]

A mechanism of energy transfer sensitization in Eu-doped LiAl 5 O 8 produced by the modified sol-gel method is proposed. The XRD results show the formation of the desired crystalline phase and the solubility limit of Eu dopant. Based in the PL results, a mechanisms of energy transfer (ET) and simultaneous excitation (SE) between the doping ion (Eu3+) and contaminating ions (Cr3+ and Fe3+) were elaborated based in the five possible dynamics. The first attributed to SE between Eu3+- Fe3+ characterized by direct excitation of Eu3+ and Fe3+ ions. The second is attributed to ET between Eu3+-Cr3+, attributed to the radiative transitions 5D 0 →7F 1,2 and Cr3+ ion. Third mechanism is similar to the energy transfer described by the second mechanism in addition to Fe3+ sensitization. The fourth and fifth are due to the SE between Eu3+-Fe3+-Cr3+. • A mechanism of energy transfer sensitization in Eu-doped LiAl 5 O 8 is proposed. • Simultaneous excitation (SE) between the Eu 3+ and contaminating ions (Cr 3+ and Fe 3+ ) were elaborated. • The effects of the Eu 3+ dopant concentration on the structural and optical properties also were investigated. [ABSTRACT FROM AUTHOR]

The photoluminescence and scintillation properties of Sn2+-doped gadolinium aluminum-silicate Gd 2 O 3 –Al 2 O 3 –SiO 2 (GAS) glasses with Si 3 N 4 as reducing agent were investigated. The glasses showed a wide emission band in the range of 360–730 nm due to the relaxation of S 1 –S 0 and T 1 -S 0 of Sn2+ luminescent centers. The luminescent intensity of Sn2+-doped GAS glasses reaches maximum at 0.3 mol% Sn2+. The lifetimes of the glasses vary between 6 and 12 μs, which related to the full width at half maximum (FWHM) of the emission spectra. Different oxides were added to explore the relationship between optical basicity and the luminescent properties of glasses. The addition of B 2 O 3 increases the photoluminescence quantum yield (PL QY) of the glasses, which is due to reduction of the Stokes shift and increment of radiative transition probability in energy level transition. The X-ray induced scintillation luminescence of the glasses were observed and studied. • The relationship between Stokes shift and optical basicity of the aluminum-silicate glasses. • High photoluminescence quantum yield (PL QY) in the Sn-doped glasses. • Quantitative analysis of the effect of phonon-electron interaction during Sn2+ luminescence. • The luminescence of Sn2+ centers excited by X-ray was observed for the first time in aluminum-silicate glasses. [ABSTRACT FROM AUTHOR]

Abstract: The photoluminescence and excitation spectra of Pr3+ activated LaPO4 has been investigated in the 1.6–300K temperature region. At room temperature, the luminescence of LaPO4:Pr3+ is composed of the interconfigurational 4f15d1 →4f2 emission transitions. However, in the 1.6–60K temperature range, the emission spectrum also consists of the intraconfigurational emission transitions that emanate from the 1S0 state. A radiative lifetime of 145ns is measured for the Pr3+ 1S0 → 1I6 emission transition in LaPO4. This is one of the shortest radiative lifetime observed for this transition in a solid. The energy position of the Pr3+ 1S0 state in LaPO4 is established by high-resolution emission spectrum at 46 375±5cm−1. A detailed analysis of the thermal quenching of the 1S0 lifetime and emission intensity is presented. It is proposed that the lowest energy state of the relaxed 4f15d1 configuration is situated energetically below that of the 1S0 state. [ABSTRACT FROM AUTHOR]

The europium ion (Eu3+) activated lithium zirconium phosphate (Li 2 Zr(PO 4) 2) phosphor samples have been synthesized by conventional solid state reaction (SSR) method at high temperature. The obtained phosphor samples crystallize in the hexagonal phase with space group R3C. Photoluminescence (PL) excitation and emission spectra have been recorded and optimum concentration was found to be 2 mol%. In the PL spectra of the synthesized phosphors, a characteristic emission peak observed at 594 nm which is ascribed to the magnetic dipole (MD) dominant transition 5D 0 →7F 1. The colorimetric parameters CCT and CIE R a values are estimated by CIE chromaticity co-ordinates. Judd-Ofelt (J-O) intensity parameters obtained from emission spectra have been used to evaluate the local site symmetry around Eu3+ ions. The J-O parameters have also been used to calculate the radiative transition probability, branching ratio and radiative lifetime. The gain bandwidth, optical gain parameter and stimulated emission cross-section are also investigated. Thermoluminescence (TL) properties of prepared phosphor have been explained in terms of glow curve and kinetic parameters. The synthesized phosphors are expected to be promising candidates for applications as solid state lighting and optical displays. • Li 2 Zr(PO 4) 2 :Eu3+ phosphors are synthesized by solid state reaction (SSR) method at high temperature. • Structural behavior thoroughly discussed by XRD, SEM, EDX and FT-IR spectroscopy. • Photoluminescence, thermo luminescence and colorimetric Properties of phosphors have been investigated. • The Judd–Ofelt parameters of Li 2 Zr(PO 4) 2 :Eu3+ phosphors have also been calculated. • The transition probability, branching ratio, radiative lifetime, gain parameter and emission cross-section are also investigated. [ABSTRACT FROM AUTHOR]

A new series of optically translucent borosilicate glasses activated with varying concentrations of Dy3+ ions were fabricated by employing melt quenching method. Spectral investigations were conducted by recording the absorption, photoluminescent (PL) excitation and PL emission for Dy3+ activated borosilicate glasses. The absorption spectral information was exposed to Judd-Ofelt (J-O) analysis to calculate various radiative properties such as transition probability, total transition probability, branching ratios and radiative lifetimes of the as synthesized glasses. The excitation spectrum recorded under 483 nm emission wavelength possess a sharp peak at 348 nm in 0.1 mol% of Dy3+ ions doped borosilicate glass. Emission spectra recorded for all the Dy3+ ions activated borosilicate glasses under 348 nm intense excitation wavelength exhibit two potential peaks in visible region at 483 nm (4F 9/2 → 6H 15/2) and 575 nm (4F 9/2 → 6H 13/2). The emission centered at 483 nm is most prominent. Radiative properties measured from the absorption spectral feature were correlated with emission spectral information to estimate emission cross-section, gain bandwidth and optical gain parameters to understand the utility of the as synthesized glasses as photonic devices. The CIE coordinates measured for all the titled glasses are in good proximity with the white light coordinates of CIE 1931 diagram. • LPZABS glasses with Dy3+ ions were prepared by using melt quench technique. • XRD recorded for all the as prepared glasses confirm the glassy nature. • The bonding nature between Dy3+ ions and the surrounding ligands is ionic in nature. • Energy transfer through dipole-dipole interaction leads to concentration quenching. • CIE of 1.5mol% of Dy in LPZABS glasses are in proximity with CIE of white light. [ABSTRACT FROM AUTHOR]

Multi-component phosphate glasses with various Nd 2 O 3 content have been prepared using conventional melt-quenching technique. X-ray diffraction was carried out to study the structure of the prepared samples and it was found that all the obtained samples are amorphous. Electrostatic F (2) , F (4) , F (6) , and spin–orbit parameters have been determined from the absorption spectra. Judd-Ofelt theory has been used to analyze and evaluate the radiative transition probability, branching ratio, and radiative lifetime for the metastable level 4 F 3/2. Luminescence spectra and experimental lifetimes give information regarding the absence of chemical clustering and suggest that the physical clustering is negligible making the glass a suitable candidate for photonic applications. Image 1 [ABSTRACT FROM AUTHOR]