UV and blue excited tunable emission of thermally stable Bi3+ sensitized Eu3+ doped calcium aluminozincate phosphor for photonic applications

Bi3+/Eu3+ co-driven calcium aluminozincate (CAZ) phosphor prepared by sol-gel route. Structural analysis was conducted based on X-ray diffractogram. Scanning Electron Microscope images were recorded using Carl Zeiss microscope. Luminescent traits of the said phosphors were identified using excitation and emission spectroscopy at room temperature and elevated temperature. The emission spectra recorded at room temperature under different excitations exhibit variation in spectral behavior. The Commision Internationale de-lElcairage coordinates shown in chromaticity diagram indicate the change in emission hue as pure blue, bluish red and finally pure red by varying the excitation wavelengths. The temperature dependent emission spectra show decrease in emission intensity with temperature and activation energy found to be 0.280 eV. The decay curves were also recorded to determine lifetime and study energy transfer between Bi3+ and Eu3+ ions. Auzel's fit conducted based on the decay lifetimes helps in evaluating quantum efficiency theoretically. All these investigations authorize the potential of Bi3+/Eu3+ doped CAZ phosphors for their utilization as color-tunable phosphor in photonic applications.

Limited energy migration and circumscribed multiphonon relaxation produced non-concentration quenching in a novel dazzling red-emitting phosphor

White LED applications are still constrained by extremely efficient narrow band red emitting phosphors. Meanwhile, the concentration quenching induced by energy migration is the main reason that limits the emission intensity of a red emitting phosphor. Therefore, developing a novel red emitting material with energy migration limitations seems necessary. Here, we proposed and realized the non-concentration quenching doping of Eu3+ ions in a Sr9Y2-2xW4O24:xEu3+ (0 ≤ x ≤ 1.0) phosphor for the first time by means of host preferential selection. By clearly investigating the crystal structure and luminescence kinetics, the long-distance between the nearby Eu3+ ions and the low phonon energy are the main reasons that suppress the energy migration and the cross-relaxation among Eu3+ ions. These advantages result in a high internal (90.47%) and external quantum efficiency (42.1%) of Sr9Eu2W4O24. With the help of the Judd-Ofelt theory and the large value of oscillator strength Ω2, Eu3+ ions are verified to occupy the non-symmetric lattice site with high color purity (94.4%). In addition, only 5.2% emission intensity loss at 140 °C can guarantee its application in LED devices. Moreover, the SYWO:Eu3+ phosphor has high thermal tolerance, high color stability, excellent moisture resistance and superior physical/chemical stability, and thus has broad practical spectral application prospects. The prepared WLED shows superior performance, and the calculated NTSC values are as high as 101.8% and 104.7%, respectively. For comparison, the optical performances of the Sr9Y2W4O24:Eu3+ phosphor outperform those of the standard commercial red phosphors, Y2O3:Eu3+ and Y2O2S:Eu3+, and almost match that of K2MnF6. These results may pave the way for fresh approaches to the study of high-performance Eu3+-activated phosphors.

Dependence of Luminous Performance on Eu3+ Site Occupation in SrIn2(P2O7)2: The Effect of the Local Environment

The photoluminescence behavior of luminescent materials with rare earth (RE) ions as a luminescence center not only depends on the element type and chemical valence of RE ions but also on their concentration and occupation in the matrix, sometimes including the interaction of the matrix and RE ions or between different RE ions. Herein, special SrIn₂(P₂O₇)₂ phosphate, assembled by monolayer [SrO₁₀]_∞ and bilayer [In₂P₄O₁₄]_∞ consisting of InO₆ units and P₂O₇ groups, was selected as the host material, and different cation positions (Sr and In) were substituted by Eu³⁺. The structure refinement in combination with Judd-Ofelt theory has shed light on the differences of the Eu³⁺ coordination environment in SrIn₂(P₂O₇)₂. The structural rigidity of the In³⁺ site is better than that of the Sr²⁺ site, making SrIn_1.92(P₂O₇)₂: Eu_0.08 superior in thermal stability. The average distance between adjacent Sr²⁺ ions is larger than that between adjacent In³⁺ ions, causing the higher quantum efficiency of Sr_0.9In₂(P₂O₇)₂: Eu_0.1. The present work demonstrates that the site occupation of Eu³⁺ has an important effect on its luminous performance. Importantly, the newly developed Eu³⁺-doped SrIn₂(P₂O₇)₂ phosphors, exhibiting outstanding luminous efficiency, favorable thermal stability, and excellent color purity, are promising red components of phosphor-based light-emitting diodes.

Enhanced luminescence properties of Ca1+xSr2−xAl2O6:Eu3+ (0 ≤ x ≤ 1) red phosphors based on composition modulation

A series of Ca_1+xSr_2−xAl₂O₆:Eu³⁺ (0 ≤ x ≤ 1) red-emitting phosphors with adjustable optical properties and excellent quantum efficiency was developed for potential applications in warm WLEDs.

Samarium-Activated La2Hf2O7 Nanoparticles as Multifunctional Phosphors

Recent developments in the field of designing novel nanostructures with various functionalities have pushed the scientific world to design and develop high-quality nanomaterials with multifunctional applications. Here, we propose a new kind of doped metal oxide pyrochlore nanostructure for solid-state phosphor, X-ray scintillator, and optical thermometry. The developed samarium-activated La₂Hf₂O₇ (LHOS) nanoparticles (NPs) emit a narrow and stable red emission with lower color temperature and adequate critical distance under near-UV and X-ray excitations. When the LHOS NPs are exposed to an energetic X-ray beam, the Sm³⁺ ions situated at the symmetric environment get excited along with those located at the asymmetric environment, which results in a low asymmetry ratio of Sm³⁺ under radioluminescence compared to photoluminescence. High activation energy and adequate thermal sensitivity of the LHOS NPs highlight their potential as a thermal sensor. Our results indicate that these Sm³⁺-activated La₂Hf₂O₇ NPs can serve as a multifunctional UV, X-ray, and thermographic phosphor.

Facile preparation of Eu3+-activated Ca7(VO4)4O nanoparticles: a blue light-triggered red-emitting platform for indoor solid-state lighting

Eu³⁺-Activated Ca₇(VO₄)₄O nanoparticles with excellent luminescence behavior and good colorific properties for blue chip based WLED applications.

Cation substitution induced excellent quantum efficiency and thermal stability in (Ca1−xSrx)9La(PO4)7:Eu2+ phosphors

Stable and efficient inorganic single-doped (Ca_1−xSr_x)₉La(PO₄)₇:Eu²⁺ (0 ≤ x ≤ 1) phosphors were demonstrated.