Shyue-Ming Jang

Ca(2)PO(4)Cl : Eu(2+): an intense near-ultraviolet converting blue phosphor for white light-emitting diodes

A blue phosphor Ca2PO4Cl:Eu2+ was synthesized by solid state reaction and evaluated as a candidate for white LEDs. The luminescent intensity of Ca2PO4Cl:Eu2+ was found to be 128% under excitation at 380 nm, 149% under 400 nm, and 247% under 420 nm, as high as that of BaMgAl10O17:Eu2+. Furthermore, Ca2PO4Cl:Eu2+ reveals high quantum efficiency and excellent thermal stability. By utilizing a mixture of blue-emitting Ca2PO4Cl:Eu2+, green-emitting (Ba,Sr)2SiO4:Eu2+ and red-emitting CaAlSiN3:Eu2+ as light converters, an intense white GaN-based n-UV-LED (400 nm) was fabricated to exhibit an excellent color-rendering index Ra of 93.4 at a correlated color temperature of 4590 K. Based on the results, we are currently evaluating the potential application of Ca2PO4Cl:Eu2+ as a blue-emitting near-UV convertible phosphor.

Eu 2+ -activated silicon-oxynitride Ca 3 Si 2 O 4 N 2 : a green-emitting phosphor for white LEDs

The green-emitting phosphor Ca3Si2O4N2:Eu2+ was synthesized using a solid-state reaction. The luminescence properties, diffuse reflection spectrum, and thermal quenching were firstly studied, and a white light-emitting diode (wLED) was fabricated using the Eu2+-activated Ca3Si2O4N2 phosphor. Eu2+-doped Ca3Si2O4N2 exhibited a broad green emission band centered between 510 and 550 nm depending on the concentration of Eu2+. The optimal doping concentration of Eu2+ in Ca3Si2O4N2 was 1 mol%. The energy transfer between Eu2+ ions proceeds by an electric multipolar interaction mechanism, with a critical transfer distance of approximately 30.08 Å. A wLED with an color-rendering index Ra of 88.25 at a correlated color temperature of 6029 K was obtained by combining a GaN-based n-UV LED (380 nm) with the blue-emitting BaMgAl10O17:Eu2+, green-emitting Ca3Si2O4N2:Eu2+, and red-emitting CaAlSiN3:Eu2+ phosphors. The results present Ca3Si2O4N2:Eu2+ as an attractive candidate for use as a conversion phosphor for wLED applications.

Luminescence and Energy Transfer Mechanism in Ca10K ( PO4 ) 7 : Eu2 + , Mn2 + Phosphor

A series of Ca 10 K(PO 4 ) 7 :Eu 2+ , Mn 2+ (CKP:Eu 2+ , Mn 2+ ) phosphors was synthesized by solid-state reaction. Under an optimal excitation of 347 nm, we have observed a blue emission band at 467 nm and a red emission band at 634 nm, which resulted from Eu 2+ and Mn 2+ , respectively. The energy transfer from Eu 2+ to Mn 2+ in CKP host matrix is of a resonant type via a dipolequadrupole mechanism. By properly varying the ratio of Eu/Mn, the emission hue can be tuned from blue (0.18,0.21), to white (0.30,0.24), and finally to red (0.35,0.24). The intensity of composition-optimized CKP:Eu 2+ is about 30% of BaMgAl 10 O 17 :Eu 2+ . The measurement of thermal quenching for CKP:Eu 2+ , Mn 2+ and yttrium aluminum garnetCe 3+ was also compared and investigated in the study. The (CKP:Eu 2+ , Mn 2+ ) phosphor may serve as a candidate for UV light-emitting diode application.

ZnB 2 O 4 :Bi 3+ ,Eu 3+ :a highly efficient, red-emitting phosphor

The novel red phosphor of Eu(3+)-Bi(3+) co-activated ZnB(2)O(4) was prepared by a solid-state reaction. The composition-optimized (Zn(0.9)Eu(0.1))B(2)O(4) phosphor exhibits a dominant emission peak at 610 nm ((5)D(0)-(7)F(2)) with CIE coordinates of (0.63, 0.36) under the excitation at 393 nm. By co-doping Bi(3+) ions in ZnB(2)O(4):Eu(3+), the emission intensity and quantum efficiency can be efficiently enhanced by an increment of 14% and 6%, respectively. The luminescence performance and thermal stability of (Zn(0.8)Bi(0.1)Eu(0.1))B(2)O(4) phosphor were found to be superior to that of the commodity phosphor, La(2)O(2)S:Eu(3+). The red-emitting borate phosphor may be potentially useful in the fabrication of white light-emitting diodes (LEDs).

Versatile phosphors BaY2Si3O10:RE (RE = Ce3+, Tb3+, Eu3+) for light-emitting diodes.

Rare-earth-activated BaY(2)Si(3)O(10) (BYSO) phosphors were synthesized via a solid-state reaction. BaY(2)Si(3)O(10):Ce(3+) yields an indigo-blue emission peak at 404 nm according to excitation at 334 nm attributed to the Ce(3+) 4f-->5d transition. BaY(2)Si(3)O(10):Tb(3+) typically generates green emission peaks resulting from the 5D4-->7FJ transition. BaY(2)Si(3)O(10):Eu(3+) exhibits red emission peaks upon excitation at 393 nm. The quantum efficiency of these phosphors was found to be 53%, 55%, and 63% of commodity. The results in this work demonstrate that these phosphors with new compositions are good candidate luminescent materials for use in plasma display panels and light-emitting diodes, excited from VUV to UV.

A Study on the Luminescence Properties of CaAlBO4 : RE3 + (RE = Ce , Tb, and Eu) Phosphors

A series of new phosphors of CaAlBO 4 :RE 3+ (RE = Ce, Tb, Eu) were synthesized by conventional solid-state reactions. The X-ray diffraction data indicate that a pure phase of CaAlBO 4 :RE 3+ can be successfully obtained. The photoluminescence (PL) spectra, quantum efficiency, and CIE coordinates of CaAlBO 4 :RE 3+ were investigated. The PL and PL excitation spectra indicate that the emission wavelengths of CaAlBO 4 :Ce 3+ are 372 and 398 nm (with full width at half maximum of 33 nm) attributed to the 4f 6 5d-4f 7 transition of the Ce 3+ activator, respectively. CaAlBO 4 :Tb 3+ displays green emission at 483, 543, 584, and 620 nm, while CaAlBO 4 :Eu 3+ shows a dominating emission peak at 621 nm, which is attributed to the Eu 3+ 5 D 0 - 7 F 2 transition. The quantum efficiencies of optimized CaAlBO 4 :Ce 3+ , CaAlBO 4 :Tb 3+ , and CaAlBO 4 :Eu 3+ were found to be 43, 21, and 19%, respectively. The phosphors may provide a new kind of luminescent material under UV excitation.

Intense blue-emitting Ca2PO4Cl:Eu2+ phosphor for near-ultraviolet converting white light-emitting diodes

Abstract A blue phosphor Ca 2 PO 4 Cl:Eu 2+ (CAP:Eu 2+ ) was synthesized by solid state reaction. The Ca 2 PO 4 Cl:Eu 2+ exhibited high quantum efficiency and excellent thermal stability. The luminescent intensity of Ca 2 PO 4 Cl:Eu 2+ was found to be 128% under excitation at 380 nm, 149% under 400 nm, and 247% under 420 nm as high as that of BaMgAl 10 O 17 :Eu 2+ . The optimal doping concentration was observed to 11 mol.% of CAP:Eu 2+ . The energy transfer between Eu 2+ ions in CAP were occurred via electric multipolar interaction, and the critical transfer distance was estimated to be 1.26 nm. A mixture of blue-emitting Ca 2 PO 4 Cl:Eu 2+ , green-emitting (Ba,Sr) 2 SiO 4 :Eu 2+ and red-emitting CaAlSiN 3 :Eu 2+ phosphors were selected in conjunction with 400 nm chip to fabricate white LED devices. The average color-rendering index R a and correlated color temperature ( T c ) of the white LEDs were found to be 93.4 and 4590 K, respectively. The results indicated that it was a promising candidate as a blue-emitting phosphor for the near-UV white light-emitting diodes.

Luminescence properties, crystal structure and LED package of potential blue-emitting phosphors - Ca 2 BN 2 F:Eu 2+

A blue-emitting phosphor - Ca2BN2F:Eu2+ was synthesized by a solid state reaction. Ca2BN2F crystallizes in the orthorhombic system with space group Pnma (No. 62) and Z = 4. The Ca2BN2F:Eu2+ exhibites broad emission and excitation bands corresponding to the allowed f→d electronic transition of Eu2+. Concentration quenching of Eu2+ emission was observed for 1 mol% due to the energy transfer between Eu2+ ions via electric multipolar interaction with the critical transfer distance of about 25.11 Å. In addition, the thermal stability and applications of blue-emitting Ca2BN2F:Eu2+ phosphors in n-UV LED have been firstly discussed in this study. The preliminary data demonstrate that the novel blue-emitting phosphor exhibits the potential to be an n-UV convertible phosphor.

Novel red-emitting garnet Na2CaTi2Ge3O12:Pr3+,Na+ phosphors

A series of red-emitting garnet Na2CaTi2Ge3O12:Pr3+,Na+ phosphors were synthesized by a high-temperature solid-state reaction. The crystal structure, luminescence properties, decay lifetime, and thermal stability were initially studied. The excitation spectra show one broad band centered at 337 nm and several sharp bands centered at 451, 462, 474 and 488 nm, which are ascribed to the 4f2 → 4f15d1 and 4f2 → 4f2 transitions of Pr3+. The emission spectra show narrow band emissions centered at 595, 609, 622 and 630 nm, which correspond to the parity-forbidden intra-configuration 4f2 → 4f2 transitions of the Pr3+ ion. The optimum concentration of Pr3+ in Na2CaTi2Ge3O12:Pr3+,Na+ was determined to be 2 mol%. Upon excitation at 451 nm, the Na2CaTi2Ge3O12:Pr3+,Na+ phosphors exhibit an intense red emission at 609 nm with CIE chromaticity coordinates of (0.6524, 0.3457). The wider color gamut of the as-synthesized Na2CaTi2Ge3O12:Pr3+,Na+ is much higher than that of commercially available materials, such as CaSi5N8:Eu2+ and CaAlSiN3:Eu2+. The results indicate that the novel red-emitting phosphors could be a potential candidate for display applications.