Luminescence of Gallates

Abstract

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Novel Energy-Transfer Route and Enhanced Luminescent Properties in YVO4:Eu3+/YBO3:Eu3+ Composite

“…Note that the relative intensity of different Stark components of 5 D 0 − 7 F 2 transition varies greatly in comparison with previous reports. Herein the maximum locates at ∼615 nm, while most of the reported values, like our bulk materials, is at ∼618 nm. ,− It suggests that Eu 3+ ions in the YVO 4 phase of the present nanocomposite should have different local symmetry from the case of pure YVO 4 :Eu 3+ nanocrystals since luminescent behavior of the 5 D 0 − 7 F 2 transitions (forced electronic dipole transition) is supersensitive to the crystal field symmetry surrounding Eu 3+ ions. Surprisingly, after excitation into the CTB in YBO 3 :Eu 3+ (240 nm), the orange-red emissions from YBO 3 :Eu 3+ (with strongest 5 D 0 − 7 F 1 line at 593 nm and relative weak 5 D 0 − 7 F 2 lines at 611 and 627 nm) are seldom observed, but the red emissions of YVO 4 :Eu 3+ appear again; the color purity is therefore improved remarkably.…”

“…In sample S2 broader excitation bands in the range of 200−350 nm are observed, which can be further decomposed into two components centered at ∼240 and 280 nm. The latter corresponds to a vanadate band in YVO 4 :Eu 3+ , originating from charge transfer from oxygen ligands to the central vanadium atom inside VO 4 3- ions, ,− while the former should dominantly correspond to the CTB in YBO 3 :Eu 3+ .

9 Excitation (left) and emission spectra (right) of sample S2 in contrast to those of sample S1 .

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“…More recently, composites attracted our attention, which not only can maintain and improve the current properties but also may create many new functions. − It is well-known that YVO 4 : Eu 3+ is another important kind of red phosphor. Owing to the efficient energy transfer from VO 4 3- to Eu 3+ and superior chromaticity (stronger 5 D 0 − 7 F 2 transition), bulk YVO 4 :Eu 3+ phosphors with the quantum yield of approximately 70% have been used in cathode ray tubes (CRT) display for more than 20 years. ,− However, for a relatively low conversion efficiency of VUV light, it is not suitable for use as PDP phosphors. To essentially improve the chromaticity of YBO 3 :Eu 3+ , here we prepared YVO 4 : Eu 3+ -modified YBO 3 :Eu 3+ composite and studied the luminescent properties in detail.…”

Electrical Conductivity of Pure and Cr3+-Doped β-Ga2O3 Thin Films

“…The shallow donor levels are associated with interstitial gallium atoms. According to the data of [21][22][23], the interstitial gallium atom must be once ionized Ga i . This shallow donor model well agrees with the hypothesis that green luminescence in -Ga 2 O 3 is related to intracentre transitions in mercury-like Ga  centres.…”

Preparation and characterization of Eu3+ activated CaSiO3, (CaA)SiO3 [A = Ba or Sr] phosphors

“…Recently, we have published Eu 3+ activated CaWO 4 (Pode and Dhoble 1997) and A-BaGd (PO 4 ) 2 (A = Li, Na or K) (Band et al 1999) as red phosphors. Eu 2+ has been extensively used in obtaining the blue component of lamp phosphors (Smets 1987), colour TV (Welker 1991), Xray imaging phosphors (Wanmaker and ter Vrugt 1967;Meijerink and Blasse 1989;Crawford and Bixner 1991;Moharil 1994), in lamps for photocopying (Wanmaker and ter Vrugt 1967) etc. In recent years, Mn activated Zn 2 SiO 4 has been found to be suitable for many more applications such as thin film electroluminescent devices (Ouyang et al 1996), plasma display panels (Cich et al 1998;Sohn et al 2000), medical imaging detector for low voltage radiography as well as fluoroscopy (Kandarakis et al 1998;Cavouras et al 2000).…”