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Europium doped borosilicate glasses were prepared in CO reducing atmosphere. The glasses were systematically investigated through XPS, photoluminescence (PL), fluorescence decay curves and X-ray excited luminescence (XEL). XPS results show that the glasses contain Eu2+ and Eu3+ at the same time. Under the excitation of 360 nm light, only a broad blue emission with peak around 440 nm due to the 5d→4f transition of Eu2+ is observed, while the emissions from Eu3+ do not appear in the PL spectra. The fluorescence decay curves were monitored at 440 nm, and the measured lifetimes are in the range of 0.17–0.42 μs. The PL results indicate that the PL emission from Eu2+ is significantly intense than the PL emissions from Eu3+. Upon X-ray excitation, two main emissions with peaks at 445 nm and 616 nm corresponding to Eu2+ and Eu3+ are obtained. The XEL results reveal that the XEL emissions from Eu3+ are comparably intense as the XEL emission from Eu2+. The results indicate that europium doped borosilicate glass could be a potential scintillating material in X-ray detection filed. [ABSTRACT FROM AUTHOR]

Ho3+-doped and Ho3+/Yb3+-codoped lead bismuth gallate (PBG) oxide glasses were prepared and their spectroscopic properties were investigated. The derived Judd–Ofelt intensity parameters (Ω2=6.81×10-20 cm2, Ω4=2.31×10-20 cm2, and Ω6=0.67×10-20 cm2) indicate a higher asymmetry and stronger covalent environment for Ho3+ sites in PBG glass compared with those in tellurite, fluoride (ZBLAN), and some other lead-contained glasses. Intense frequency upconversion emissions peaking at 547, 662, and 756 nm as well as infrared emissions at 1.20 and 2.05 μm in Ho3+/Yb3+-codoped PBG glass were observed, confirming that energy transfer between Yb3+ and Ho3+ takes place, and a two-phonon-assisted energy transfer from Yb3+ to Ho3+ ions was determined by the calculation using phonon sideband theory. The 1.20 μm emission observed was primarily due to the weak multiphonon deexcitation originated from the small phonon energy of PBG glass (∼535 cm-1). A large product of emission cross-section and measured lifetime (9.93×10-25 cm2 s) was obtained for the 1.20 μm emission and the gain coefficient dependence on wavelength with population inversion rate (P) was performed. The peak emission cross-section for 2.05 μm emission was calculated to be 4.75×10-21 cm2. The relative mechanism of Ho3+-doped and Ho3+/Yb3+-codoped PBG glasses on their spectroscopic properties was also discussed. Our results suggest that Ho3+/Yb3+-doped PBG glasses are a good potential candidate for the frequency upconversion devices and infrared amplifiers/lasers. [ABSTRACT FROM AUTHOR]

Abstract Eu3+ doped tellurite scintillating glasses were prepared by the conventional melt-quenching method. The physical and luminescent properties of glasses were investigated by DTA, density, transmittance spectra, photoluminescence spectra, and X-ray excited luminescence (XEL) spectra. The densities of the glasses are in the range from 5.89 g/cm3 to 6.05 g/cm3. The glasses exhibit intense red emissions upon 393 nm light and X-ray excitations. The maximum integral XEL intensity of the glasses is about 6% of that of commercial Bi 4 Ge 3 O 12 (BGO) scintillating crystal. The results reveal that Eu3+ doped tellurite glass could be a scintillator candidate used in X-ray detection field. [ABSTRACT FROM AUTHOR]

Transparent Tb 3+ -doped glass ceramics containing BaF 2 nanocrystals were prepared by melt-quenching method with subsequent heat treatment. The XRD and EDS results showed the precipitated crystalline phase in the glass matrix was BaF 2 . Under 376 nm light, Tb 3+ doped oxyfluoride glass ceramics containing BaF 2 nanocrystals showed more intense green emission than the as-made glass, and the emission intensity increased with increasing heat treatment temperature and time. The lifetimes of 541 nm emission of Tb 3+ doped oxyfluoride glass ceramics were longer than that of as-made glass, which are in the range from 3.00 ms to 3.55 ms. Under X-ray excitation, the green emission was enhanced in the glass ceramics compared to the as-made glass. The results indicate Tb 3+ doped oxyfluoride glass ceramics containing BaF 2 nanocrystals could be a material candidate for X-ray glass scintillator for slow event detection. [ABSTRACT FROM AUTHOR]

Abstract: Orange emitting Sr2.96−x Ba x SiO5: Eu2+ phosphors have been synthesized by a method using Sr2SiO4 instead of simple oxides and carbonate as precursor. The photoluminescence properties, radiative lifetime and formation process were investigated by PL spectra, lifetime decay and XRD analysis, respectively. X-ray diffraction analysis indicates that the phosphor has a single phase of Sr3SiO5 without residual Sr2SiO4 and BaSi4O9 phases. Under 460nm excitation, the emission band of Sr2.96−x Ba x SiO5: Eu2+ has a red-shift from 580–598nm due to varied Ba2+ concentration. Particularly, the emission intensity of Sr2.56Ba0.4SiO5: 0.02Eu2+ sample increased significantly in comparison with the commercial SSE phosphor. The radiative lifetime τ 0 are estimated to be 1.999, 2.316, 2.716 and 2.932μs for samples of x=0, 0.2, 0.4 and 0.6, respectively. It indicates that Eu2+ ions are in different surroundings and the Sr2+ sites were substituted by Ba2+ completely. Compare with the conventional solid-state reaction method, the Sr2.96−x Ba x SiO5: Eu2+ phosphors synthesized by this method show higher crystallinity and more efficient orange emission. [Copyright &y& Elsevier]

Abstract: A novel Ce3+/Eu2+ co-activated LiSr4(BO3)3 phosphor has been synthesized by traditional solid-state reaction. The samples could display varied color emission from blue towards white and ultimately to yellow under the excitation of ultraviolet (UV) light with the appropriate adjustment of the relative proportion of Ce3+/Eu2+. The resonance-type energy transfer mechanism from Ce3+ to Eu2+ in LiSr4(BO3)3:Ce3+, Eu2+ phosphors is dominant by electric dipole–dipole interaction, and the critical distance is calculated to be about 29.14Å by the spectra overlap method. White light was observed from LiSr4(BO3)3:mCe3+, nEu2+ phosphors with chromaticity coordinates (0.34, 0.30) upon 350nm excitation. The LiSr4(BO3)3:Ce3+, Eu2+ phosphor has potential applications as an UV radiation-converting phosphor for white light-emitting diodes. [Copyright &y& Elsevier]

Abstract: A novel orange-yellow-emitting Ba2LiB5O10:Eu2+ phosphor has been synthesized by traditional high temperature solid state reaction. A monoclinic crystal structure of Barium lithiumborates Ba2LiB5O10 was verified by the investigation of X-ray diffraction (XRD). The compound crystallizes in the space group of P121/m1(11) (Z=2) with the unit cell parameters a=4.414(1)Å, b=14.576(2)Å, c=6.697(2)Å and β=104.26(2)°. Barium and lithium atoms are located in distorted octahedral and tetrahedral oxygen coordinations, respectively. Upon around 365nm excitation, the Eu2+-activated Ba2LiB5O10 phosphors exhibit a single broad emission band with the maximum at about 587nm, due to the 4f65d→4f7(8S7/2) transition of Eu2+. This work investigates the relationship between luminescence properties and structural characterization of the Ba2LiB5O10: Eu2+. This newly developed phosphor shows high potential as a phosphor conversion for white LED applications. [Copyright &y& Elsevier]

Abstract: Y6Si3O9N4:Ce3+ phosphor was prepared by a solid-state reaction in reductive atmosphere. X-ray powder diffraction (XRD) analysis confirmed the formation of Y6Si3O9N4:Ce3+. Scanning electron microscopy (SEM) observation indicated that the microstructure of the phosphor consisted of irregular fine grains with an average size of about 5μm. Photoluminescence (PL) measurements showed that the phosphor can be efficiently excited by near ultraviolet (UV) or blue light excitation, and exhibited bright green emission peaked at about 525nm. Compared with Ce3+-doped Y4Si2O7N2 phosphors, Ce3+-doped Y6Si3O9N4 phosphors showed longer wavelengths of both excitation and emission. The Y6Si3O9N4:Ce3+ is a potential green-emitting phosphor for white LEDs. [Copyright &y& Elsevier]

NaGd (WO 4) 2 nanocrystals were successfully precipitated from silicate glasses for the first time and transparent glass ceramics were prepared. High diffraction peaks and well-resolved lattice fringes confirm the high crystallinity of NaGd (WO 4) 2 in the glass ceramics. The enhanced photoluminescence emission spectra, long fluorescence lifetime and the increased transition intensity ratio between 5D 0 →7F 2 and 5D 0 →7F 1 transitions of Eu3+ ions suggest that Eu3+ ions were incorporated into the precipitated NaGd(WO 4) 2 nanocrystals. Gradually enhanced upconversion emission spectra of Er3+ ions in the glass ceramics were observed with the increased thermal treatment time. The dependence of luminescence intensity ratio (LIR) on temperature was determined at the temperature range of 303 K–573 K. The maximum absolute sensitivity S a is 0.012 K−1 at 542 K and the maximum relative sensitivity S r is 1.178% at 303 K, which are attributed to the enrichment of Er3+ ions in the precipitated NaGd (WO 4) 2 nanocrystals and may be used for optical temperature sensors. • Transparent oxyfluoride glass ceramics containing NaGd(WO 4) 2 nanocrystals were fabricated. • Greatly enhanced upconversion emission spectra of Er3+ ions in the glass ceramics were observed. • The maximum absolute sensitivity Sa is 0.012K–1 at 542 K. [ABSTRACT FROM AUTHOR]