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• Li 2 ZnTi 3 O 8 :Eu3+ phosphors were synthesized by solid state reaction method. • Intense red emission at 612 nm under 309 and 393 nm excitations. • The internal quantum efficiency was 48.91 %. • Possess excellent thermal stability, high color purity and warm CCT values. • Potential candidate to be used in pc-WLEDs under UV excitation. Embracing phosphor converted white light-emitting diodes (pc-WLEDs) represent a significant step towards efficient and sustainable energy sources, herein we report the synthesis, structural and optical properties of Eu3+ doped Li 2 ZnTi 3 O 8 phosphor for the first time. A series of Li 2(1- x) ZnTi 3 O 8 : x Eu3+ phosphors (x = 0, 0.02, 0.05, 0.08, 0.1 and 0.3 mol) were prepared by the high temperature solid state reaction method. The structural and morphological characterisation of prepared samples were done using X -ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), Energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared (FTIR) spectroscopy. The XRD analysis confirmed the cubic structure and purity of the samples with the incorporation of Eu3+ ions. The presence of functional groups was detected from FTIR and compositional elements from EDX. FESEM and TEM images revealed similar agglomerated block like structures. The optical properties were analysed using diffuse reflectance spectrum (DRS) and photoluminescence (PL) spectra. Under 309 and 393 nm excitation, characteristic emission peaks of Eu3+ ions corresponding to 5D 0 → 7F J (J = 0,1,2,3 and 4) transitions were observed in which the intense emission was recorded at 612 nm. Under both the excitations, the optimum concentration of prepared phosphor was 8 mol% (x = 0.08 mol) and the mechanism for concentration quenching was found to be dipole - dipole interaction. The decay lifetime of prepared phosphors was in the milliseconds range and the internal quantum efficiency was measured to be 48.91 %. Li 2(1- x) ZnTi 3 O 8 : 0.08Eu3+ phosphor has an activation energy of 0.163 eV and holds good thermal stability. Also, for the optimum sample, the Commission International de I'Eclairage (CIE) coordinates were detected at (0.6333, 0.3663) and (0.6344, 0.3651) for 309 and 393 nm excitation respectively, which lies in the orange - red region with super color purity and warm correlated color temperature (CCT) values. Therefore, obtained results suggest that the prepared Li 2(1- x) ZnTi 3 O 8 : x Eu3+ phosphors are suitable candidates for its use in pc-WLEDs. [ABSTRACT FROM AUTHOR]

• Ca 9 Al(PO 4) 7 :Sm3+ nanophosphors have been synthesized via urea-assisted solution-combustion method. • Crystal structure analysis of Ca 9 Al 0.90 (PO 4) 7 :0.10Sm3+ nanophosphor has been reported on Rietveld treatment. • Optical properties for Ca 9 Al(PO 4) 7 host lattice are calculated from DFT. • Energy band gap for Ca 9 Al(PO 4) 7 host is obtained experimentally and theoretically. • These nanophosphors have potential applications in solid state lighting devices. Nanocrystalline phosphors of composition Ca 9 Al(PO 4) 7 : x Sm3+ (x = 0.01–0.16) were successfully synthesized using a urea-assisted highly efficient solution combustion technique. The structural, morphological, and photoluminescence features of the series of white powdered samples were studied using powder X-ray diffraction, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and photoluminescence characterization techniques. The structural framework and crystal phase purity of Ca 9 Al 0.90 Sm 0.10 (PO 4) 7 phosphor were investigated by Rietveld refinement analysis. The results showed that the replacement of Al3+ ions with Sm3+ ions in Ca 9 Al 0.90 Sm 0.10 (PO 4) 7 nanophosphor didn't alter the host lattice crystal structure and a trigonal lattice having R3c (161) space group was established. Meanwhile, the average particle size evaluated from the Scherrer equation was further confirmed by transmission electron microscopic studies revealing a size domain ranging from 35-60 nm. Structural optimization of the pure host via first-principle routing disclosed the density of states and electronic band structure having a band gap of 4.738 eV, which was found to be quite comparable to the experimentally observed value (4.37 eV) from the diffuse reflectance spectra. Many key optical properties, such as optical conductivity, extinction coefficient, loss function, and refractive index were determined by using a calculated dielectric function. Furthermore, photoluminescence studies inferred that 10 mol% of Sm3+ ion in Ca 9 Al(PO 4) 7 host matrix gave the best luminescence emission intensity. Detailed photoluminescent analysis of Ca 9 Al(PO 4) 7 : x Sm3+ phosphors demonstrated that on excitation at 401 nm, an intense reddish-orange emission was received at 600 nm (4G 5/2 → 6H 7/2 transition). The critical distance for energy migration came out to be 22 Å which strongly favors the mechanism behind luminescence quenching as dipole-quadrupole interactions resulting from the over-doping of activator ions. The chromaticity coordinates (0.5216, 0.3630) were obtained using MATLAB computations. These results favor the applicability of Sm3+ doped Ca 9 Al(PO 4) 7 phosphors as the reddish-orange emitter in near-ultraviolet excited white light-emitting diodes. [Display omitted] [ABSTRACT FROM AUTHOR]

A new series of Zinc telluro-fluoroborate glasses (ZTFB) doped with Dy 3+ ions with the chemical composition (30−x) B 2 O 3 + 30TeO 2 + 16ZnO + 10ZnF 2 + 7CaF 2 + 7BaF 2 + xDy 2 O 3 (where x = 0.05, 0.1, 0.25, 0.5, 1 and 2 in wt%) have been synthesized by the conventional melt quenching technique and the prepared glass samples were characterized through XRD, FTIR, UV-Vis-NIR optical absorption, photoluminescence and decay spectral measurements. The XRD patterns have been recorded to confirm the amorphous nature. The FTIR spectral measurements were carried out to identify the functional groups present in the title glasses. From the energy band positions of the absorption spectra, bonding parameters ( β ¯ and δ) have been calculated to identify the covalent/ionic nature of the metal-ligand bond present in the prepared glasses. The Judd-Ofelt (JO) intensity parameters Ω λ (λ = 2, 4 and 6) have been calculated from the oscillator strengths of the different absorption bands to understand the nature of the ligand environment around the Dy 3+ ions. The radiative parameters such as transition probability (A), stimulated emission cross-section ( σ P E ), radiative lifetime (τ R ) and branching ratios (β R ) corresponding to the 4 F 9/2 → 6 H 15/2 , 4 F 9/2 → 6 H 13/2 , and 4 F 9/2 → 6 H 11/2 emission transitions have been determined using JO parameters and the refractive index values. The CIE chromaticity coordinates were calculated from the luminescence spectra to explore the dominant emission colour of the title glasses and the obtained results were discussed in detail and reported. [ABSTRACT FROM AUTHOR]