Jiaguo Wang

Ca1 − 2x Eu x Li x MoO4 : A Novel Red Phosphor for Solid-State Lighting Based on a GaN LED

A novel red phosphor Ca 1 - 2 x Eu x Li x MoO 4 with high performance is reported. Under the excitation of 254 nm UV light, its luminescent intensity is comparable to that of the commercial red phosphor Y 2 O 3 :Eu 3 + . With high Eu 3 + concentration, the phosphor has strong excitation due to f-f transitions of Eu 3 + appearing around 395 nm. Thus, it is a promising material for solid-state lighting based on GaN light-emitting diode (LED).

Preparation and X-ray characterization of low-temperature phases of R2SiO5 (R = rare earth elements)

Low-temperature phases of R2SiO5 (R 5 Y, Tb, Dy, Ho, Er, Tm, and Yb) were synthesized by the sol-gel method. The X-ray powder diffraction patterns for these new phases were indexed with the monoclinic unit cell, and the unit cell parameters were refined. The structure of Y2SiO5 with the space group P21/c was determined by powder diffraction data.

Influence of Rare Earth Elements (Sc, La, Gd, and Lu) to the Luminescent Properties of FED Blue Phosphor Y 2SiO5 : Ce

The emission spectra of Y 2 SiO 5 :Ce were analyzed by Gaussian peak fitting. The emission mainly can be attributed to the transitions of 5d to 2 F 5/2 and 2 F 7/2 of Ce 3+ ions. A weak peak at ∼460 nm arises from an independent luminescent center. Both the luminescent intensity and the peak height ratio are affected by Ce 3+ content. For choosing an optimized Ce 3+ content, the balance between brightness and color saturation was considered. Sc 3+ and La 3+ cannot replay Y 3+ to form solid solutions and doping them reduced luminescence very much. Y 3+ can be replaced by Gd 3+ and Lu 3+ to form solid solution in some ranges. The replacement of Gd 3+ decreased the luminescence, whereas Lu 3+ enhances the luminescence about 20% under cathode ray excitation. Ludoping also improves color saturation.

The composition, luminescence, and structure of Sr8[Si4O12]Cl8:Eu2+

Abstract Based on the investigation of phases present and luminescence of the system Sr 8 [Si 4x O 4+8x ]Cl 8 :Eu 2+ , the correct formula for this material was determined as Sr 8 [Si 4 O 12 ]Cl 8 :Eu 2+ rather than Sr 4 Si 3 O 8 Cl 4 :Eu 2+ , which had been assumed previously. The structure of this material was refined by the Rietveld method using powder X-ray diffraction data, which has a tetragonal unit cell with space group I4/m, Z = 2, a = 1.11814(1)nm, c = 0.95186(1) nm. In this structure, Sr has one site; therefore, when Eu 2+ is doped in, the luminescence gives only one broad emission peak.

Photoluminescent Properties of Phosphors in the System Ca x Cd1 − x MoO4 : Eu3 + , Li +

The luminescent properties of the new red phosphors in the solid solution system Ca x Cd 1 - A MoO 4 :Eu 3 + , Li + are reported. Their dominating emission peaks are at 615 nm, which satisfies color purity. Under the excitation of ∼320 nm UV light, some selected samples have luminescent intensity 30% higher than that of the commercial red phosphor Y 2 O 2 S:Eu 3 + . Therefore, it is a promising material for N 2 plasma display application.

Cathodoluminescence of Eu3 + , Tb3 + , and Tb3 + ­ Eu3 + Pair-Activated Zn3Ta2 O 8

Cathodoluminescent measurements were conducted to Eu 3+ , Tb 3+ , and Eu 3+ -Th 3+ pair-doped Zn 3 Ta 2 O 8 as well as undoped Zn 3 Ta 2 O 8 . Tb 3+ -doped samples mainly gave the characteristic emission of Tb 3+ with green color, while in Eu 3+ -doped samples, the dominating emission was the blue band that was contributed by the host emission and Eu 2+ emission. For Eu 3+ and Tb 3+ codoped Zn 3 Ta 2 O 8 , the spectrum mainly consisted of the characteristic emissions of Tb 3+ and a strong blue emission; the emissions from Eu 3+ appeared very weak. The blue emission of Eu 2+ may be understood by using the reduction mechanism (Eu 3+ + e → Eu 2+ ), and the charge transfer mechanism (Eu 3+ + Tb 3+ → Eu 2+ + Tb 4+ ). For the Eu 3+ and Tb 3+ codoped samples, although the Eu 3+ emission was very weak, it still increased with Tb 3+ content, this was because the energy transfer from Tb 3+ to Eu 3+ also occurred.

Luminescence enhancement of BaMgSiO4:Eu2+ by adding borate as flux

Abstract The luminescence of Eu 2+ in BaMgSiO 4 with BaB 2 O 4 as flux was studied. The emission spectrum of the phosphor consisted of two bands, peaking at about 398 nm and 515 nm, which were attributed to the emissions from different Eu 2+ sites in the lattice. When the BaB 2 O 4 flux was applied, the intensity of the 398 nm emission was not clearly affected, but the intensity of the 515 nm emission was enhanced by about ten times. Gaussian fitting showed that the emission band at around 515 nm could actually be resolved into two bands with peak wavelengths of 499 nm and 521 nm, respectively. The assignments of the emission bands to the cation sites were carried out according to the values of bond valence. The overlapping of the 398 nm emission band on the excitation band of 515 nm emission implied that energy transfer could occur from the luminescent center related to the 398 nm emission to the center related to the 515 nm emission, and the energy transfer process remarkably enhanced the intensity of the 515 nm emission band. The phosphor had strong excitation at around 350-400 nm and emitted a bright green luminescence. Thus it could have applications as a green component in solid-state lighting devices assembled by near-UV Light Emitting Diodes (LED) combined with tricolor phosphors.