Dan Zhang,Taifang Zhang,Mekhrdod Kurboniyon,Peng Wang,Chonggeng Ma
A novel garnet-type phosphor, Gd2–yYyLuAl4GaO12: Ce3+, was synthesized via a high-temperature solid-state reaction to address the demand for efficient green-emitting materials in solid-state lighting. By employing a cation substitution strategy (Y3+/Gd3+ codoping), the photoluminescence performance was significantly enhanced: the quantum efficiency increased from 86.79 to 96.86%, accompanied by a tunable emission shift from yellow to green (560–520 nm). Moreover, the thermal stability at 423 K improved dramatically from 40.79 to 92.98%, surpassing those of commercial green phosphors. Structural and spectral analyses revealed that the optimized crystal field splitting and enhanced lattice rigidity, induced by cation substitution, effectively suppressed nonradiative transitions, thereby boosting both quantum efficiency and thermal stability. A prototype white light-emitting diode (WLED) fabricated with Y2LuAl4GaO12: Ce3+ phosphor exhibited excellent performance, including a high color rendering index (Ra = 91), low correlated color temperature (CCT = 3043 K), and good color stability under varying driving currents. These findings highlight the significant promise of Gd2–yYyLuAl4GaO12: Ce3+ as a superior green-emitting phosphor for advanced WLED systems, providing a feasible pathway for designing outstanding thermal stability and color-tunable luminescent materials via cationic engineering.
Wenzhi Wang,Jinkai Li,Zhengyang Zhang,Zongming Liu
The new systems of the (Gd 0.95- x Dy 0.05 Tb x ) 2 (WO 4 ) 3 ( x = 0–0.1) and (Gd 0.95- y Dy 0.05 Eu y ) 2 (WO 4 ) 3 ( y = 0–0.2) phosphors have been successfully obtained using the hydrothermal method at 900 °C in this work. The crystal structure, morphology, PL/PLE spectra, fluorescence and decay analysis have been studied in detail via the combined techniques of XRD , FE-SEM, PLE/PL spectra and decay kinetic. The phase-pure of the (Gd 0.95- x Dy 0.05 Tb x ) 2 (WO 4 ) 3 and (Gd 0.95- y Dy 0.05 Eu y ) 2 (WO 4 ) 3 with good dispersions have been formed at the lower sintering temperature of 900 °C. Under 273 nm and 270 nm excitation (the 6 P 7/2 → 8 S 7/2 transitions of Gd 3+ ), the Gd 2 (WO 4 ) 3 :Dy 3+ /Tb 3+ and Gd 2 (WO 4 ) 3 :Dy 3+ /Eu 3+ phosphors exhibit both Dy 3+ (yellow, at 574 nm) and Tb 3+ (green, at 547 nm) as well as Dy 3+ (yellow, at 574 nm) and Eu 3+ (red, at 616 nm) emissions, respectively. The presences of WO 4 2- , Gd 3+ and Dy 3+ excitation bands on the PLE spectra by monitoring the Tb 3+ and Eu 3+ emissions directly provide an evidence of energy transfer of WO 4 2- →Tb 3+ , Gd 3+ →Tb 3+ and Dy 3+ →Tb 3+ , as well as WO 4 2- →Eu 3+ , Gd 3+ →Eu 3+ and Dy 3+ →Eu 3+ , respectively. The quenching concentrations of both two systems are determined to be 7 at% ( x = 0.07 for Tb 3+ ) and 10 at% ( y = 0.10 for Eu 3+ ), and the quenching mechanisms of both two systems are mainly due to the Tb 3+ -Tb 3+ and Eu 3+ -Eu 3+ energy transfers, respectively. The color-tunable emission can be achieved though adjusting the relative content ratios of Dy 3+ /Tb 3+ or Dy 3+ /Eu 3+ , which has been verified by the CIE chromaticity coordinates analysis. The energy transfer efficiencies of Dy 3+ →Tb 3+ and Dy 3+ →Eu 3+ have been calculated, and the energy transfer mechanisms have been analyzed in detail. The (Gd 0.95- x Dy 0.05 Tb x ) 2 (WO 4 ) 3 and (Gd 0.95- y Dy 0.05 Eu y ) 2 (WO 4 ) 3 phosphors with color-tunable emission may have a potential application for w-LEDs.
Four new acyloxy bridged Ln III 2 compounds [Ln 2 (L) 2 (acac) 2 (EtOH) 2 ] (Ln(III) = Gd ( 1 ), Tb ( 2 ), Dy ( 3 ), and Ho ( 4 ), Hacac = acetylacetone, and H 2 L = pyridine-2-carboxylic acid (3-ethoxy-2-hydroxy-benzylidene)-hydrazide) have been prepared by a polydentate Schiff base ligand under solvothermal condition. The single-crystal X-ray structure study reveals that 1 – 4 are isostructural and contain a parallelogram Ln 2 O 2 core. Magnetic study reveals that antiferromagnetic interaction exists in compound 1 . More importantly, compound 1 displays well cryogenic magnetic refrigeration property (−Δ S m = 28.2 J kg −1 K −1 , T = 2.0 K and Δ H = 70 kOe); while compound 3 exhibits evident single-molecule magnet behavior under zero-field condition (Δ E / k B = 26.8 K, τ 0 = 1.05 × 10 −7 s).
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