Oxy-fluoride glasses with composition of 25SiO2-65PbF2-9.4AlF3-0.1HoF3-0.5YbF3 were prepared. Their up-conversion fluorescence characteristics were investigated by 980 nm laser. Two emission peaks were observed at 540...Oxy-fluoride glasses with composition of 25SiO2-65PbF2-9.4AlF3-0.1HoF3-0.5YbF3 were prepared. Their up-conversion fluorescence characteristics were investigated by 980 nm laser. Two emission peaks were observed at 540 and 650 nm. The up-conversion mechanism and processes were analyzed. The relationship between pumping power and relative intensity of emissions was discussed. From the dependence, it is known that the emissions centered at 540 and 650 nm are both attributed to two-photon process.展开更多
Different concentrations of Mg^（2＋） -doped hexagonal phase NaGdF_4：Yb^（3＋）, Er^（3＋）nanocrystals（NCs） were synthesized by a modified solvothermal method. Successful codoping of Mg^（2＋）ions in upconversio...Different concentrations of Mg^（2＋） -doped hexagonal phase NaGdF_4：Yb^（3＋）, Er^（3＋）nanocrystals（NCs） were synthesized by a modified solvothermal method. Successful codoping of Mg^（2＋）ions in upconversion nanoparticles（UCNPs） was supported by XRD, SEM, EDS, and PL analyses. The effects of Mg^（2＋）doping on the morphology and the intensity of the upconversion（UC） emission were discussed in detail. It turned out that with the concentration of Mg^（2＋）increasing, the morphology of the nanoparticles turn to change gradually and the UC emission was increasing gradually as well. Notably the UC fluorescence intensities of Er^（3＋）were gradually improved owing to the codoped Mg^（2＋）and then achieved a maximum level as the concentration of Mg^（2＋）ions was 60 mol% from the amendment of the crystal structure of β-NaGdF_4：Yb^（3＋）,Er^（3＋）nanoparticles. Moreover, the UC luminescence properties of the rare-earth（Yb3＋, Er^（3＋）） ions codoped NaGdF_4 nanocrystals were investigated in detail under 980-nm excitation.展开更多
This paper reports on the spectral results of Nd3＋/yb3＋ ions codoped 50P2Os-30ZnO-20SrO （PZS, in mol.%） glasses which were prepared by a melting technique. The glass transition temperature and spectroscopic proper...This paper reports on the spectral results of Nd3＋/yb3＋ ions codoped 50P2Os-30ZnO-20SrO （PZS, in mol.%） glasses which were prepared by a melting technique. The glass transition temperature and spectroscopic properties of these glasses were estimated. From the absorption spectra, Judd-Ofelt （J-O） intensity parameters （Ωk）, were calculated. Using J-O intensity parameters, several radiative properties such as spontaneous transition probabilities （AR）, radiative branching ratios （fiR） and radiative lifetimes （rR） were determined for the exciting levels of the Nd3＋ ions. The large value of the stimulated integrated cross-section and the lifetimes of Nd3~ level revealed the potential of the present glasses as a candidate for generating laser emission at 1.06/am as continuous wave laser action and exploited for optical device fabrication. A broad emission band from 950 to 1100 nm was detected when the Nd3＋/yb3＋ was co-doped in PZS glasses excited by 805 nm lighting diode （LD）. The energy transfer process from Nd3＋--→Yb3＋ in co-doped phos- phate glasses was described in this paper.展开更多
We report on transparent Ni^2＋-doped MgO-Al2O3-SiO2 glass ceramics with broadband infrared luminescence. Ni^2＋-doped MgO-Al2O3-SiO2 glass is prepared by using the conventional method. After heat treatment at high te...We report on transparent Ni^2＋-doped MgO-Al2O3-SiO2 glass ceramics with broadband infrared luminescence. Ni^2＋-doped MgO-Al2O3-SiO2 glass is prepared by using the conventional method. After heat treatment at high temperature, MgAl2O4 crystallites are precipitated, and their average size is about 4.3 nm. No luminescence is detected in the as-prepared glass sample, while broadband infrared luminescence centred at around 1315 nm with full width at half maximum （FWHM） of about 300 nm is observed from the glass ceramics. The observed infrared emission could be attributed to the ^3T2g（^3F）→^3A2g（^3F） transition of octahedral Ni^2＋ ions in the MgAl2O4 crystallites of the transparent glass ceramics. The product of the fluorescence lifetime and the stimulated emission cross section is about 1.6×10^-24 s cm^2.展开更多
Yb3＋ and Er3＋ ions co-doped NaYF4 nanocrystals were synthesized with different amounts of NaOH via oleic acid（OA）-assisted hydrothermal process. X-ray diffraction（XRD）, scanning electron microscopy（SEM）, trans...Yb3＋ and Er3＋ ions co-doped NaYF4 nanocrystals were synthesized with different amounts of NaOH via oleic acid（OA）-assisted hydrothermal process. X-ray diffraction（XRD）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, Fourier transform infrared spectroscopy（FTIR）, and photoluminescence spectra were used to characterize the products. The result indicated that the introduction of Na OH into the initial reaction solution effectively promoted the cubic（α-） to hexagonal（β-） phase transition of NaYF4：Yb3＋,Er3＋ nanocrystals, while excessive amount of Na OH favored the formation of α-NaYF4：Yb3＋,Er3＋ nanocrystals. Besides, with the increase of Na OH amount, the morphologies of β-NaYF4：Yb3＋,Er3＋ nanocrystals varied from irregular nanobranch to uniform nanorod. Further investigation revealed that the addition of Na OH could facilitate the deprotonation of OA, leading to the formation of oleate（OA–）, and meanwhile increased the concentration of OH– ions, inducing consequently the phase transition and morphology evolution of NaYF4：Yb3＋,Er3＋ nanocrystals. Moreover, the upconversion luminescence properties of NaYF4：Yb3＋,Er3＋ nanocrystals were systematically investigated. It was found that the upconversion emissions not only depended on the phase and morphology but also were influenced by the surface groups.展开更多
In this paper,the energy levels of Yb^（3＋） ions in yttrium aluminum borate（YAB） crystal were calculated from a first-principles approach with an optimized defect structure obtained from the WIEN2 k package and a ...In this paper,the energy levels of Yb^（3＋） ions in yttrium aluminum borate（YAB） crystal were calculated from a first-principles approach with an optimized defect structure obtained from the WIEN2 k package and a traditional fitting method using a more reliable computer package.The calculated results were then compared with those obtained from a re-calculation using the values of parameters given by some previous researchers.Three types of likely mistakes in the previous researcher＇s paper,namely over fitting,incorrect use of irreducible representation,and errors in the calculations for the EPR parameters were clearly identified and effectively rectified in this paper.The electron paramagnetic resonance（EPR） parameters,which included g factors like g（//） and g⊥ and hyperfine structure constants A// and A⊥,were also calculated through the perturbation method and compared with some observed values available in literature.There was reasonable agreement found with the experimental values which lay between the values obtained from the first-principles calculation（g//=4.000 and g⊥=1.391;A//=1032 and A⊥=360 in 10^（-4） cm^（-1） for ^（171）Yb^（3＋）） and those from the fitting approach（g//=3.612 and g⊥=1.702;A//=867 and A⊥=470 in 10^（-4） cm^（-1） for ^（171）Yb^（3＋））.展开更多
文摘Oxy-fluoride glasses with composition of 25SiO2-65PbF2-9.4AlF3-0.1HoF3-0.5YbF3 were prepared. Their up-conversion fluorescence characteristics were investigated by 980 nm laser. Two emission peaks were observed at 540 and 650 nm. The up-conversion mechanism and processes were analyzed. The relationship between pumping power and relative intensity of emissions was discussed. From the dependence, it is known that the emissions centered at 540 and 650 nm are both attributed to two-photon process.
基金supported by the National High Technology Research and Development Program of China(Grant No.2013AA032205)the Key Project of Beijing Scientific Committee,China(Grant No.D161100003416001)+1 种基金the Fundamental Research Funds for the Central Universities,China(Grant No.2016JBM066)the National Natural Science Foundation of China(Grant Nos.51272022 and 11474018)
文摘Different concentrations of Mg^（2＋） -doped hexagonal phase NaGdF_4：Yb^（3＋）, Er^（3＋）nanocrystals（NCs） were synthesized by a modified solvothermal method. Successful codoping of Mg^（2＋）ions in upconversion nanoparticles（UCNPs） was supported by XRD, SEM, EDS, and PL analyses. The effects of Mg^（2＋）doping on the morphology and the intensity of the upconversion（UC） emission were discussed in detail. It turned out that with the concentration of Mg^（2＋）increasing, the morphology of the nanoparticles turn to change gradually and the UC emission was increasing gradually as well. Notably the UC fluorescence intensities of Er^（3＋）were gradually improved owing to the codoped Mg^（2＋）and then achieved a maximum level as the concentration of Mg^（2＋）ions was 60 mol% from the amendment of the crystal structure of β-NaGdF_4：Yb^（3＋）,Er^（3＋）nanoparticles. Moreover, the UC luminescence properties of the rare-earth（Yb3＋, Er^（3＋）） ions codoped NaGdF_4 nanocrystals were investigated in detail under 980-nm excitation.
文摘This paper reports on the spectral results of Nd3＋/yb3＋ ions codoped 50P2Os-30ZnO-20SrO （PZS, in mol.%） glasses which were prepared by a melting technique. The glass transition temperature and spectroscopic properties of these glasses were estimated. From the absorption spectra, Judd-Ofelt （J-O） intensity parameters （Ωk）, were calculated. Using J-O intensity parameters, several radiative properties such as spontaneous transition probabilities （AR）, radiative branching ratios （fiR） and radiative lifetimes （rR） were determined for the exciting levels of the Nd3＋ ions. The large value of the stimulated integrated cross-section and the lifetimes of Nd3~ level revealed the potential of the present glasses as a candidate for generating laser emission at 1.06/am as continuous wave laser action and exploited for optical device fabrication. A broad emission band from 950 to 1100 nm was detected when the Nd3＋/yb3＋ was co-doped in PZS glasses excited by 805 nm lighting diode （LD）. The energy transfer process from Nd3＋--→Yb3＋ in co-doped phos- phate glasses was described in this paper.
文摘We report on transparent Ni^2＋-doped MgO-Al2O3-SiO2 glass ceramics with broadband infrared luminescence. Ni^2＋-doped MgO-Al2O3-SiO2 glass is prepared by using the conventional method. After heat treatment at high temperature, MgAl2O4 crystallites are precipitated, and their average size is about 4.3 nm. No luminescence is detected in the as-prepared glass sample, while broadband infrared luminescence centred at around 1315 nm with full width at half maximum （FWHM） of about 300 nm is observed from the glass ceramics. The observed infrared emission could be attributed to the ^3T2g（^3F）→^3A2g（^3F） transition of octahedral Ni^2＋ ions in the MgAl2O4 crystallites of the transparent glass ceramics. The product of the fluorescence lifetime and the stimulated emission cross section is about 1.6×10^-24 s cm^2.
基金supported by the Shanghai Scientific Research Innovation Projects(14ZZ037)the Basic Research Project of Shanghai Science and Technology Commission(12JC1408500)the Fundamental Research Funds for the Central Universities(2011KJ018)
文摘Yb3＋ and Er3＋ ions co-doped NaYF4 nanocrystals were synthesized with different amounts of NaOH via oleic acid（OA）-assisted hydrothermal process. X-ray diffraction（XRD）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, Fourier transform infrared spectroscopy（FTIR）, and photoluminescence spectra were used to characterize the products. The result indicated that the introduction of Na OH into the initial reaction solution effectively promoted the cubic（α-） to hexagonal（β-） phase transition of NaYF4：Yb3＋,Er3＋ nanocrystals, while excessive amount of Na OH favored the formation of α-NaYF4：Yb3＋,Er3＋ nanocrystals. Besides, with the increase of Na OH amount, the morphologies of β-NaYF4：Yb3＋,Er3＋ nanocrystals varied from irregular nanobranch to uniform nanorod. Further investigation revealed that the addition of Na OH could facilitate the deprotonation of OA, leading to the formation of oleate（OA–）, and meanwhile increased the concentration of OH– ions, inducing consequently the phase transition and morphology evolution of NaYF4：Yb3＋,Er3＋ nanocrystals. Moreover, the upconversion luminescence properties of NaYF4：Yb3＋,Er3＋ nanocrystals were systematically investigated. It was found that the upconversion emissions not only depended on the phase and morphology but also were influenced by the surface groups.
基金supported by the CRD(RG10/2015-2016R)Dean’s Research Grants of FLASS(CRS-1:04119)Ed UHK and National Natural Science Foundation of China(11547146)
文摘In this paper,the energy levels of Yb^（3＋） ions in yttrium aluminum borate（YAB） crystal were calculated from a first-principles approach with an optimized defect structure obtained from the WIEN2 k package and a traditional fitting method using a more reliable computer package.The calculated results were then compared with those obtained from a re-calculation using the values of parameters given by some previous researchers.Three types of likely mistakes in the previous researcher＇s paper,namely over fitting,incorrect use of irreducible representation,and errors in the calculations for the EPR parameters were clearly identified and effectively rectified in this paper.The electron paramagnetic resonance（EPR） parameters,which included g factors like g（//） and g⊥ and hyperfine structure constants A// and A⊥,were also calculated through the perturbation method and compared with some observed values available in literature.There was reasonable agreement found with the experimental values which lay between the values obtained from the first-principles calculation（g//=4.000 and g⊥=1.391;A//=1032 and A⊥=360 in 10^（-4） cm^（-1） for ^（171）Yb^（3＋）） and those from the fitting approach（g//=3.612 and g⊥=1.702;A//=867 and A⊥=470 in 10^（-4） cm^（-1） for ^（171）Yb^（3＋））.
