Mengkai Lv

Absorption and photoluminescence characteristics of Co2+:MgAl2O4 nanocrystals embedded in sol–gel derived SiO2-based glass

Abstract Co 2+ :MgAl 2 O 4 nanocrystals embedded in SiO 2 -based glass have been prepared by heating the gels of composition 5MgO–6Al 2 O 3 –89SiO 2 – x CoO ( x =0.2, 0.4, 0.6, 1.0) (mol%). When the gel samples were heated up to 1000 °C, MgAl 2 O 4 nanocrystals were precipitated and Co 2+ ions were located in the tetrahedral sites in MgAl 2 O 4 nanocrystals. X-ray diffraction analysis shows that the diameter of MgAl 2 O 4 crystal is ∼5–15 nm. Absorption and emission bands in the visible and near infrared regions have been observed from transparent Co 2+ :MgAl 2 O 4 /SiO 2 nanocomposites. The observed absorption and emission spectra are characteristic of tetrahedral Co 2+ in crystals. The intensity of absorption bands increases with the increasing of heat-treatment temperature and Co 2+ concentration, while with the increasing of Co 2+ concentration, the fluorescence intensity decreases and the fluorescence spectra in the visible range show a red shift. The crystal field parameter D q of 405 cm −1 and the Racah parameters B of 752 m −1 and C of 3388 cm −1 were calculated for tetrahedral Co 2+ ions.

A Novel Nonlinear Optical Complex Crystal with an Organic Ligand Coordinated through an O Atom: Tetrathiocyanatocadmiummercury‐Dimethyl Sulfoxide

A novel nonlinear optical complex crystal with an organic ligand coordinated through an O atom: tetrathiocyanatocadmiummercury-dimethyl sulfoxide, [CdHg(SCN) 4 (H 6 C 2 OS) 2 ], (CMTD) is reported for the first time. Single crystals have been grown by temperature-lowering method, the crystal structure has been determined, and some physical properties are given. The relations between the crystal structure and nonlinear optical properties are also discussed.

A novel organometallic nonlinear optical complex crystal : Cadmium mercury thiocyanate dimethyl-sulphoxide

Abstract A novel nonlinear optical organometallic complex crystal: cadmium mercury thiocyanate dimethylsulphoxide (CdHg(SCN)4(H6C2OS)2, CMTD) is reported for the first time. The single crystal has been grown by a temperature-lowering method, the crystal structure has been determined, and some physical properties arepresented. The relations between the crystal structure and nonlinear optical properties are also discussed.

Crystal growth and characterization of La3Ga5SiO14 single crystals

Abstract An almost colorless La3Ga5SiO14 (LGS) single crystal with 26 mm in diameter and 25 mm in length was grown by the Czochralski technique. The coloration of the crystal depends on the growth atmosphere. The cutoff wavelength of the colorless LGS crystal is shorter than an annealed crystal and the piezoelectric properties of the former are nearly equal to those of the colored one.

Optical absorption of Co2+-doped silica gel-derived glasses

Abstract Monolithic samples of silica and Co-doped silica gels were obtained by the sol–gel method and heat-treated at temperatures from 40 to 1000 °C. The colors of Co-doped silica samples depended on heat-treatment temperature. Ultraviolet, visible and near-infrared (NIR) absorption spectra of the samples heated at different temperatures were recorded and compared with those of undoped silica samples. Results showed that 0.4 wt.% Co-doped silica samples heated at temperatures ranging 750–1000 °C exhibited broad absorption band in the range of 1200–1600 nm, and the intensity of the absorption band increased with heat-treatment temperatures. Co-doped silica glass is potential to be used as a kind of laser passive Q-switching material in NIR range.

Preparation and characterization of Co/sup 2/-doped ZnO-Al/sub 2/O/sub 3/-SiO/sub 2/ glass-ceramics by the sol-gel method

Transparent glass-ceramics containing Co2+: zd1zo4 nanocrystals were obtained by the sol-gel process for the fEst time. The gels of composition 89Si02-5.9A1203-4.9ZnO-0.2CoO (ZAS) were prepared at room temperature, and heat-treated at different temperatures. The microstructure and optical properties of the heated samples were studied by using X-ray difiaction (XRD), transmission electron microscopy (TEM), infrared spectroscopy and optical absorption spectra. After heat treatment at temperature over 900°C, the Co2+: ZnAlzO4 nanocrystals were precipitated from ZAS system. TEM analysis indicated that nanometer sized CO”: ZnAl204 crystals were dispersed in the SiO2-based glass. Co2+ ions were located in tetrahedral sites in ZnAlzO4 nanocrystals. The CO”: z d l z o 4 crystallite size was in the range 10-15nm. The samples heated at temperatures ranging 900-950°C exhibited a broad absorption band in the range of 1200-1600nm, which was due to tetrahedral CO*+ ions in 2 1 ~ 4 1 2 0 4 nanocrystals. The intensity of the absorption band increased with the increasing of heat-treatment temperature. This indicates that more CO’’ ions enter into tetrahedral sites of ZnAlz04 crystal in place of Zn2’ ions with the increasing of heat-treatment temperature. This kind of glass-ceramic is chemically stable and can be easily polished. As a result, the transparent glass-ceramics have a potential as passive Q-switches for Er: glass laser.