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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 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]