Structure and Luminescent Properties of Sm^(3+) Doped SrO-MgO-SiO_2 Glass Ceramics

A new type of samarium ion activated luminescent glass ceramics with main crystal phase of melilite was prepared. The effect of heat-treatment temperature on the structure of glass ceramics was investigated by X-ray diffraction analysis（XRD）, scanning electron microscope（SEM） and fluorescence spectrometer. In the Sm^3＋ doped SrO-MgO-SiO2 glass ceramic, its excitation spectra are in the wavelength range of 350-500 nm, and its excitation peaks are at 360 nm, 374 nm, 404 nm, 417 nm, and 475 nm with the host excitation peak of 404 nm, showing a strong orange-red luminescence when using 404 nm violet to excite it, and its emission peaks are at 564 nm, 600 nm and 648 nm with the host emission peak at 600 nm. The increase in the heat-treatment temperature has no infl uence on the position of the fl uorescent spectra. However, with the increase of heat-treatment temperature, the intensity of fl uorescence spectrum shows an increasing tendency. The increase in the concentration of Sm3＋ also improves the intensity of the fl uorescent spectra. In the experimental concentration range（0.05mol%-0.30mol%）, a special concentration quenching phenomenon happens.

Frequency Up-conversion Luminescence Properties and Mechanism of Tm^(3+) /Er^(3+)/Yb^(3+) Co-doped Oxyfluorogermanate Glasses

Oxyfluoride glasses were developed with composition 60GeO 2 ·10AlF 3 ·25BaF 2 ·（1.95-x）GdF 3 · 3YbF 3 ·0.05TmF 3 ·xErF 3 （x=0.02,0.05,0.08,0.11,0.14,0.17）in mole percent.Intense blue（476 nm）,green（524 and 546 nm）and red（658 nm）emissions which identified from the 1G 4 →3H 6 transition of Tm3＋and the（2H 11/2 ,4S 3/2 ）→4I 15/2 ,4F 9/2 →4I 15/2 transitions of Er3＋,respectively,were simultaneously observed under 980 nm excitation at room temperature.The results show that multicolor luminescence including white light can be adjustably tuned by changing doping concentrations of Er3＋ion or the excitation power.In addition,the energy transfer processes among Tm3＋,Er3＋and Yb3＋ions,and up-conversion mechanisms are discussed.

Synthesis and photoluminescent properties of Eu^3＋/Dy^3＋ doped SrO-Al2O3-SiO2 glass-ceramics

Eu^3＋/Dy^3＋ single-doped and co-doped 6SrO-3Al2O3-91SiO2 and 12SrO-6Al2O3-82SiO2 glass and glass-ceramics were synthesized successfully by a sol-gel method. The prepared samples were characterized by the X-ray diffraction, high-resolution transmission electron microscopy, photoluminescent spectra and X-ray photoelectron spectroscopy. The effect of annealing temperature, doped ions and matrix component on the structure and the photoluminescent characteristics was systematically studied. The higher temperature was helpful to form nanocrystals and the amount of SrO and Al2O3 could better disperse the rare earth ions in matrix at suitable temperature, and both of them could improve the luminescent intensity. Meanwhile, the doped ions could change the luminescent color by single, codoped and energy transfer. The Sr2SiO4 nanocrystals were observed in silicates glasses and became larger with the increase of the annealing temperature and the luminous efficiency of rare-earth（RE） ions could be enhanced when the samples changed from glass state to glass-ceramic state. The results indicated that the photoluminescent properties could be changed through controlling the doped ions, annealing temperature and matrix component.

Energy transfer and frequency upconversion in Er^(3+)-Yb^(3+) codoped oxy-fluoro-tungstosilicate glasses

Er3＋-Yb3＋ codoped oxy-fluoro-tungstosilicate glasses with infrared-to-visible frequency upconversion luminescence were prepared by melting quenching in air.The effects of Er3＋ doping on the optical properties of the samples were measured by means of techniques such as optical absorption spectra and photoluminescence spectra.The results showed that intense green and red signals centered at 546 and 665 nm,corresponding to the 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3＋ by a multiphoton stepwise phonon-assisted excited-state absorption process,respectively,were simultaneously observed by exciting the samples with a diode laser operating at 980 nm at room temperature.The upconversion process was found very sensitive to Er3＋ content at a constant Yb2O3 content of 5 mol.%.With the increase of Er3＋ content from 0.5% to 1.5%,the upconversion intensity increased gradually.Further increasing of Er3＋ content to 3.0% resulted in a significant fluorescence quenching.Moreover,the possible upconversion mechanisms were discussed based on the energy-matching conditions and the quadratic dependence on excitation power.

Effect of Nd^(3+) on spectroscopic properties of lithium borate glasses

The spectroscopic properties of lithium borate glasses as a function of Nd3＋ ions concentration were reported.Optical absorption spectra of these glasses showed a number of absorption bands in ultra violet and visible region.Optical absorption edge was found to shift towards the longer wavelength（red shift） with increase in Nd2O3.Luminescence spectra revealed three major bands at 902, 1063 and 1334 nm which was due to 4F3/2→4I9/2, 11/2 ＆13/2 transitions of Nd3＋ ions.Luminescence intensity was maximum for 1 mol.% Nd2O3 and further increase in Nd2O3 resulted in luminescence quenching.The luminescence quenching behavior at higher concentration of Nd2O3 was attributed to the Nd3＋-Nd3＋ interaction in the glass matrix.An absorption and emission property of these glasses suggested that these glasses could be useful for 1.06 μm infrared laser applications.

Multi-wavelength excitable europium-doped borosilicate glasses for orangered emission:composition-induced structure and valence variation

Europium-doped borosilicate glasses were prepared by melt-quenching procedure in the air.The mixed valence of Eu 2＋ and Eu 3＋ was identified by photoluminescence spectrum and electron paramagnetic resonance（EPR）.The existence of mixed valence was observed owing to the unequivalent substitution and de-polymerization network of the as-prepared borosilicate glasses.The variation of the glass composition in B 2 O 3 /BaO ratios changed the stability of the Eu 3＋ ions distinctly.In particular,as-prepared borosilicate glasses exhibited a tri-wavelength light excitable spectra centered at 397,466 and 534 nm to give the broadened orange-red emission at around 592 and 617 nm,due to supersensitive transitions of Eu 3＋ ions.This simultaneous tri-wavelength excitation happened to correspond with the emitting wavelength from near ultraviolet,blue AlInGaN chips and that from YAG：Ce 3＋.The total quantum yield（QY） of the Eu-doped glasses under 466 nm excitation was evaluated to be 10%,potentially providing a versatile combination with the europium-doped borosilicate glasses for red component addition to improve the quality of white light.