Shujian Tian

Novel phosphors of Eu3+, Tb3+ or Bi3+ activated Gd2GeO5

Abstract Novel phosphors of Eu 3+ , Tb 3+ or Bi3+ doped Gd2GeO5 were synthesized and their photoluminescent and cathodoluminescent properties were investigated. (Gd1−xEux)2GeO5 and (Gd1−xTbx)2GeO5 formed continuous solid solution in the range of x=0.0–1.0. Gd2GeO5:Eu3+ and Gd2GeO5:Bi3+ presented bright red and blue luminescence for both UV and cathode ray excitation, respectively. While Gd2GeO5:Tb3+ gave bright green cathodoluminescence. In all three phosphors, the energy transfer from Gd3+ to activators (e.g. Eu 3+ , Tb 3+ or Bi3+) occurred.

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 Sc and La to the Luminescent Properties of FED Blue Phosphor Y 2SiO5 : Ce

Luminescent properties of Sc 3+ and La 3+ doped (Y 0.995 Ce 0.005 ) 2 SiO s phosphors were studied. In the Sc 3+ doped system (Y 0.995-x Sc x Ce 0.005 ) 2 SiO 5 , the solid solution extends to x = 0.65, but in the La 3+ doped system (Y 0.995-x, La x Ce 0.005 ) 2 SiO 5 , the solid solution range is not over the La 3+ content of x = 0.05. For La 3+ doped samples, the photoluminescence (PL) increases about 30% and cathodoluminescence (CL) increases about 10%. Additionally the color saturation is also improved with La 3+ doping. The mechanisms for these improvements are discussed. For the Sc 3+ doped samples, both PL and CL, clearly decrease. These phosphors may be useful in field emission displays TEED).

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.

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.

New Phases of R 3GaO6 ( R = Rare Earth Elements) and Their Luminescent Properties

Six new phases with formula R 3 GaO 6 (R = rare earth elements Y, Eu, Tb, Dy, Ho and Er) were prepared and they have iso-structure with orthorhombic Nd 3 GaO 6 . The unit cell parameters were refined for all new phases. The ionic radii for 7-coordinated Nd 3+ and Ho 3+ were obtained by regression analyses, the values of which are 0.1188(2) and 0.1098(1) nm, respectively. In addition, preliminary research was conducted on PL and CL properties of Eu 3+ , Tb 3+ , or Bi 3+ -doped Y 3 GaO 6 and Gd 3 GaO 6 . Among the phosphors studied in present research, Y 3 GaO 6 :Eu 3+ , Y 3 GaO 6 :Tb 3+ and Gd 3 GaO 6 :Bi 3+ show bright red, green, and blue luminescence. Further optimizations are necessary to promote their luminescent properties for field emission display applications.