New yellow Ba_(0.93)Eu_(0.07)Al_(2)O_(4) phosphor for warm-white light-emitting diodes through single-emitting-center conversion

Phosphor-converted white light-emitting diodes for indoor illumination need to be warm-white(i.e.,correlated color temperature,4000 K)with good color rendition(i.e.,color rendering index.80).However,no single-phosphor,single-emitting-center-converted white light-emitting diodes can simultaneously satisfy the color temperature and rendition requirements due to the lack of sufficient red spectral component in the phosphors’emission spectrum.Here,we report a new yellow Ba_(0.93)Eu_(0.07)Al_(2)O_(4) phosphor that has a new orthorhombic lattice structure and exhibits a broad yellow photoluminescence band with sufficient red spectral component.Warm-white emissions with correlated color temperature,4000 K and color rendering index.80 were readily achieved when combining the Ba_(0.93)Eu_(0.07)Al_(2)O_(4) phosphor with a blue light-emitting diode(440–470 nm).This study demonstrates that warm-white light-emitting diodes with high color rendition(i.e.,color rendering index.80)can be achieved based on single-phosphor,single-emitting-center conversion.

Advanced purification and comprehensive utilization of yellow phosphorous off gas

Yellow phosphorous is an important raw material in the chemical industry. However, during the production of yellow phosphorous, high concentrations of carbon monoxide and other impurities are released. Without appropriate purification and removal, this off gas has potential to cause severe pollution problems once released. Purified yellow phosphorous off gas can be beneficially reused as a raw material in chemical production for synthesis of high value-added chemical reagents. In this paper, the significance of purification and reutilization of yellow phosphorous off gas are explored. The principles, processes, and main characteristics of the technologies for purification and reuse of yellow phosphorus off gas （including technical measurements of impurity reduction, relevant engineering cases, and public acceptance of the technologies） are summarized. In view of the existing problems and scientific development require- ments, this paper proposes green production based several recommendations for on the concept of recycle economics. We conclude that advanced purification and comprehensive reutilization can be an effective solution for heavy pollution resulting from yellow phosphorous off gassing.

Eu^(2+) and Dy^(3+) codoped(Ca,Sr)_7(SiO_3)_6Cl_2 highly efficient yellow phosphor

Eu2＋ and Dy3＋ codoped （Ca, Sr）7（SiO3）6C12 yellow phosphors were successfully synthesized by self-flux method. The structure, morphology and photoluminescence properties were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and photoluminescence spectra. The as-prepared phosphor showed a broad emission spectrum centered at 550 nm for Eu2＋ single-doped phosphor, while located at 548 544 nm for the Eu2＋, Dy3＋ codoped samples under excitation at 380 nm light. The emission intensity was greatly improved when Dy3＋ was doped into the （Ca,Sr）7（SiO3）6C12：Eu2＋ system. The composition-optimized sample with 3 mol.% of Dy3＋ and constant 10 tool.% of Eu2＋ exhibited a 220% PL enhancement compared to the phosphor with 10 tool.% Eu2＋ single-doped. Meanwhile, it was found that the quantum efficiency of phosphor namely （Ca,Sr）7（SiO3）6Cl2：3 tool.% Dy3＋ 10 mol.% Euz＋ could get up to 24.6%. The synthesized yellow-emitting （Ca,Sr）7（SiO3）6C12：Dy3＋,Eu2＋ is a promising candidate as high-efficiency yellow phosphor for NUV-excited white LEDs.

White light emission in Pr^(3+),Tb^(3+):CaYAlO_4 phosphor

In this work, the synthesis and photoluminescence characteristics of two new phosphors Pr3+: CaYAlO4(CYA) and Pr3+/Tb3+: CYA for light emitting diodes(LEDs) are investigated. 0.5%(atom percentage) Pr3+: CYA exhibits the largest bright yellow emission by varying the Pr3+ concentration, owing to the cross-relaxation process of 3P0 +3H4→ 1G4+1G4. The energy level diagram in Pr3+: CYA, especially the positions of 4f5 d level and 1S0 level, is discussed. By co-doping Tb3+ ions, the color coordinates of Pr3+/Tb3+: CYA phosphor can be tuned from yellow to white region. Finally, the strongest luminescence emission with color coordinates of(0.339, 0.364) located in the white region can be obtained in 0.3%Tb3+/0.5%Pr3+: CYA phosphor.

Luminous efficacy and color rendering index of high power white LEDs packaged by using red phosphor

We packaged a series of high power white LEDs by covering the blue LED chips with yellow phosphor, red phosphor and the two phosphors mixed by appropriate mass ratio, respectively, and discussed the excitation and emission spectrum of yellow phosphor and red phosphor and the characteristics of the LEDs. We found that the luminous efficacy of the white LEDs covered with the two phosphors mixed by appropriate mass ratio was lower than that of the white LEDs covered with yellow phosphor, but the color rendering index was improved observably.