Te-Wen Kuo

A Green-Emitting Phosphor Sr3La ( PO4 ) 3 : Ce3 + , Tb3 + with Efficient Energy Transfer for Fluorescent Lamp

3+ ,Tb 3+ have been synthesized by a solid-state reaction. The energy transfer from Ce 3+ to Tb 3+ is a resonant type via a dipole–dipole mechanism with an energy-transfer critical distance of 7.6 A. By utilizing the principle of energy transfer and appropriate tuning of activator contents, we have also made an attempt to observe a strong green emission performance displayed by this phosphor for use as a coating material on compact fluorescent lamps CFLs. The results clearly indicate that the luminous efficiency based on Sr3La0.67Ce0.08Tb0.25PO43 was found to be 69 lm/W. The good luminous efficiency and lumen maintenance 2000 h, 91.8% of the green-emitting CFL demonstrate that this phosphor can be suitable for application on a short UV fluorescent lamp. Additionally, the Sr3La0.67Ce0.08Tb0.25PO43 green phosphor has advantages of

Emission color variation of (Ba,Sr) 3 BP 3 O 12 :Eu 2+ phosphors for white light LEDs

A series of alkaline earth borophosphate phosphors, (Ba,Sr)(3)BP(3)O(12) doped with Eu(2+) ions, were synthesized by a solid state reaction. Two emission bands at 465 nm and 520 nm were attributed to the f-d transitions of doped Eu(2+) ions occupying in two different cation sites in host lattices and emission color variation was observed by substituting the M(2+) sites, which was rationalized in terms of two competing factors of the crystal field strength and bond covalence. Green and bluish-white pc-LEDs were fabricated by combination of a 370 nm near-UV chip and composition-optimized Ba(3)BP(3)O(12):Eu(2+) and (Ba,Sr)(3)BP(3)O(12):Eu(2+) phosphors, respectively. The series of phosphors may serve as a promising green and bluish-white luminescent materials used in fabrication of near UV-based white pc-LEDs.

Thermally stable green Ba 3 Y(PO 4 ) 3 :Ce 3+ ,Tb 3+ and red Ca 3 Y(AlO) 3 (BO 3 ) 4 :Eu 3+ phosphors for white-light fluorescent lamps

A class of thermal stable of green-emitting phosphors Ba(3)Y(PO(4))(3):Ce(3+),Tb(3+) (BYP:Ce(3+),Tb(3+)) and red-emitting phosphors Ca(3)Y(AlO)(3)(BO(3))(4):Eu(3+) (CYAB:Eu(3+)) for white-light fluorescent lamps were synthesized by high temperature solid-state reaction. We observed a decay of only 3% at 150 °C for BYP:0.25Ce3+,0.25Tb3+ (3% for LaPO4:Ce(3+),Tb(3+)), and a decay of 4% for CYAB:0.5Eu(3+) (7% for Y(2)O(3):Eu(3+), 24% for Y(2)O(2)S:Eu(3+)). The emission intensity of composition-optimized Ba(3)(Y(0.5)Ce(0.25)Tb(0.25))(PO(4))(3) is 70% of that of commercial LaPO(4):Ce(3+),Tb(3+) phosphors, and the CIE chromaticity coordinates are found to be (0.323, 0.534). The emission intensity of Ca(3)(Y(0.5)Eu(0.5))(AlO)(3)(BO(3))(4) is 70% and 83% of those of Y(2)O(3):Eu(3+) and Y(2)O(2)S:Eu(3+) phosphors, respectively, and the CIE chromaticity coordinates are redder (0.652, 0.342) than those of Y(2)O(3):Eu(3+) (0.645, 0.347) and Y(2)O(2)S:Eu(3+) (0.647, 0.343). A white-light fluorescent lamp is fabricated using composition-optimized Ba(3)(Y(0.5)Ce(0.25)Tb(0.25))(PO(4))(3) and Ca(3)(Y(0.5)Eu(0.5))(AlO)(3)(BO(3))(4) phosphors and matching blue-emitting phosphors. The results indicate that the quality of the brightness and color reproduction is suitable for application in shortwave UV fluorescent lamps. The white-light fluorescent lamp displays CIE chromaticity coordinates of x = 0.33, y = 0.35, a warm white light with a correlated color temperature of 5646 K, and a color-rendering index of Ra = 70.

Novel yellowish-orange Sr 8 Al 12 O 24 S 2 :Eu 2+ phosphor for application in blue light-emitting diode based white LED

A new yellowish-orange phosphor, Sr(8)Al(12)O(24)S(2):Eu(2+), was synthesized by the solid-state method and its photoluminescence properties were investigated by excitation and emission spectra. Its excitation band is extending from 400-500 nm, which is adaptable to the emission band of blue LED chips (450-470 nm). Upon the excitation of 450 nm light, the phosphor exhibits strong yellowish-orange emission centered at 605 nm with good thermal stability. A white light-emitting diode (W-LED) that consists of a blue LED chip (approximately 470 nm) and a (Sr(0.92)Eu(0.08))(8)Al(12)O(24)S(2) phosphor is demonstrated. The CIE1931 chromaticity coordinates (x, y) are (0.34, 0.25), the correlated color temperature (CCT) is 4300 K, and the luminous efficacy of this W-LED is 14.2 lm/W at room temperature and with a forward-bias current of 400 mA.

Intense violet-blue-emitting Ba 2 AlB 4 O 9 Cl:Eu 2+ phosphors for applications in fluorescent lamps and ultraviolet-light-emitting diodes

We synthesized a violet-blue phosphor Ba(2)AlB(4)O(9)Cl:Eu(2+) with a solid-state reaction. The excitation and emission spectra of this phosphor showed that all were broadband due to 4f(7)-4f(6)d(1) transitions of Eu(2+). The phosphors with different Eu(2+) concentrations presented violet-blue luminescence for ultraviolet [(UV) 250-390nm] excitation. The optimum concentration of Eu(2+) in Ba(2)AlB(4)O(9)Cl:Eu(2+) is determined to be 6mol.%. The luminous efficiency was found to be 8.1lm/W for the violet-blue fluorescent lamp and 3.2lm/W for the violet-blue phosphor-converted light-emitting diode, respectively. Ba(2)AlB(4)O(9)Cl:Eu(2+) would be a promising phosphor for converting the UV radiation to violet-blue emission for a novel high light-conversion efficiency phototherapy illuminator.