| Rare earth ions or transition metal ions doped glass ceramics containing spinel-type nanocrystals combine the advantage of the optical crystal and the optical glass. Because of their optical properties are close to the crystals, until now, there have been important applications for them in the white LED, passive tunable Q laser and near infrared optical fiber amplifier, solar cells and so on. However, due to the current existing disadvantages of optical characteristics from the oxide glass and lacking mechanical and chemical properties from the nanocrystals, and hope to explore the influence of the compositions and preparation technique on the micro-structure and the luminescence poperties of the glass ceramics, the transparent glass ceramics containing spinel-type nanocrystals with doped ions of rare earth ions or transition metal ions have been synthesized by sol-gel method, and the micro-structure and photolumimescence properties have been investigated in this thesis. Especially, the active ions such as the rare-earth ions (Eu3+, Tb3+) and transparent ions (Co2+) were doped in the glass ceramics containing spinel-type nanocrystals (ZnGa2O4, γ-Ga2O3 & ZnAl2O4). And the Differential thermal analysis and Thermal gravity analysis (DTA-TG), Fourier translation infrared spectroscopy (FT-IR), X-ray diffraction (XRD), luminesce spectroscopy, and Transmission electron microscope (TEM) were used to research the influence of the composition, heat treatment temperature, and doping activating ions to the micro-structure and the properties of the materials. The main results are as follows.The transparent glass ceramics containing spinel-type nanocrystal, such as ZnGa2O4, γ-Ga2O3 and ZnAl2O4 with doped ions of rare earth ions or transition metal ions were successfully gained by improving the process parameters of sol-gel method. Especially, it synthesized successfully the high crystal (more than 12 mol% ZnAl2O4 and more than 20 mol% γ-Ga2O3), too. And then, the performance optimization throught the controlling of microstructure is achieved. It reveals the main control factors of the nano-crystalline phase structure in the glass ceramics, the evolution law of the glass ceramics structure with the heat treatment.The results of the XRD show that the spinel-type ZnGa2O4 nanocrystal appears in glass matrix as the dry-gels heat-treated in the range of temperature from 800℃ to 900℃. But the samples are devitrified with the extra trigonal Zn2SiO4 and hexagonal SiO2 crystals when the heat-treating temperature up to 1000℃.The ZnGa2O4-SiO2 glass ceramics doped Tb3+, Eu3+ and co-doped with Tb3+/Eu3+ were synthesized by the sol-gel method, respectively. The influence of the composition and the thermal temperature on the microstructure and the photoluminescence properties of the glass ceramics doped with different rare-earth ions were studied. The excitation spectra demonstrate the energy transfer from ZnGa2C>4 nanocrystal to the Tb3+and Eu3+ ions in the glass ceramics. The emission spectra indicates that there is the green light for Tb3+ ions or the red light for Eu3+ions observed in the emissions spectra respectively, in the Tb3+ions and Eu3+ions co-doped Tb3+/Eu3+ZnGa2O4-SiO2 glass ceramics heat-treated at 900℃. It is very interesting that while light can be realized by combination of these two emissions with the blue light emission from the ZnGa2O4 nanocrystal, when the Tb3+/Eu3+ ZnGa2O4-SiO2 glass ceramics are excited by the ultraviolet light.The transparent glass ceramics containing different concentration of γ-Ga2O3 nanocrystals (1Eu3+:Xγ-Ga203-10ZnO-(89-X)Si02 (X=0,5,10, 15,20))were successfully synthesized, respectively. XRD and TEM observation reveal that γ-Ga2O3 nanocrystals are formed and distributed homogeneously among the amorphous matrix. Importantly, the Eu+ emission intensity of the nano-composite with 20% mol%γ-Ga2O3 is about 5.5 times stronger than that of the sample without γ-Ga2O3, which is attributed to the effective energy transfer from the γ-Ga2O3 nanocrystal to the rare earth Eu3+ions.The Eu+:Sn02-SiO2 glass ceramics with rutile-type nanocrystals were synthesized to compare the photoluminescence of the spinel-type glass ceramics. The emission spectra excited at 280 nm showed that there was stack split in the Eu3+:SnO2 glass ceramics heat-treated up to 800℃, which means some Eu3+ have inserted the SnO2 nanocrystals.The transparent Co2+:ZnAl2O4-SiO2 block glass ceramics with doped of transition metal ions Co2+ were synthesized by sol-gel method, too. The average size of the ZnAl2O4 nanocrystals were 12-14 nm. The result shows that the glass ceramics exhibit a broad absorption band in the range of 1200-1600 nm. And the absorption coefficient enhances with the increasing of heat-treating temperature, which is characteristic of 4A2â†'4T1(4F) transition from the tetrahedral Co2+ ions. It is found that the absorption cross section reaches 1.15×10-19 cm2 when the heat-treating temperature is up to 1000℃, which means it can be applied in the passive Q-switch turnable laser.ZnAl2O4-SiO2 transparent glass ceramics co-doped with Tb3+ and Eu3+ were successfully synthesized by the sol-gel method. The glass ceramics exhibit the excellent luminescence, which changes from green to the red emission with adjusting the concentration of the Tb3+/Eu3+. It suggests the potential application as optical functional materials. |
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