Qiao Yanbo

Spectroscopic properties of Nd3+-doped high silica glass prepared by sintering porous glass

A new kind of Nd3+, -doped high silica glass (SiO2 > 96% (mass fraction)) was obtained by sintering porous glass impregnated with Nd3+, ions. The absorption and luminescence properties of high silica glass doped with different Nd3+, concentrations were studied. The intensity parameters Omega(t) (t = 2, 4, 6), spontaneous emission probability, fluorescence lifetime, radiative quantum efficiency, fluorescence branching ratio, and stimulated emission cross section were calculated using the Judd-Ofelt theory. The optimal Nd3+ concentration in high silica glass was 0.27% (mole fraction) because of its high quantum efficiency and emission intensity. By comparing the spectroscopic parameters with other Nd3+ doped oxide glasses and commercial silicate glasses, the Nd3+-doped high silica glasses are likely to be a promising material used for high power and high repetition rate lasers.

Investigations on Valence-Change Behaviors of Europium Ions in Eu-Doped Aluminate and Silicate Phosphors

Abstract Compounds of Sr 3 Al 2 O 6 : Eu, Sr 4 Al 14 O 25 : Eu, and BaZnSiO 4 : Eu were synthesized by high-temperature solid state reactions. The doping Eu 3+ ions were partially reduced to Eu 2+ in Sr 4 Al 14 O 25 : Eu and BaZnSiO 4 : Eu prepared in an oxidizing atmosphere, N 2 + O 2 . However, such an abnormal reduction process could not be performed in Sr 3 Al 2 O 6 : Eu, which was also prepared in an atmosphere of N 2 + O 2 . Moreover, even though Sr 3 Al 2 O 6 : Eu was synthesized in a reducing condition CO, only part of the Eu 3+ ions was reduced to Eu 2+ . The existence of trivalent and divalent europium ions was confirmed by photoluminescent spectra. The different valence-change behaviors of europium ions in the hosts were attributed to the difference in host crystal structures. The higher the crystal structure stiffness, the easier the reduction process from Eu 3+ to Eu 2+ .

High Quantum Efficiency and High Concentration Erbium-Doped Silica Glasses Fabricated by Sintering Nanoporous Glasses

A new method was used to prepare erbium-doped high silica (SiO2% > 96%) glasses by sintering nanoporous glasses. The concentration of erbium ions in high silica glasses can be considerably more than that in silica glasses prepared by using conventional methods. The fluorescence of 1532 nm has an FWHM (Full Wave at Half Maximum) of 50 nm, wider than 35 nm of EDSFA (erbium-doped silica fiber amplifer), and hence the glass possesses potential application in broadband fiber amplifiers. The Judd-Ofelt theoretical analysis reflects that the quantum efficiency of this erbium-doped glass is about 0.78, although the erbium concentration in this glass (6 x 103) is about twenty times higher than that in silica glass. These excellent characteristics of Er-doped high silica glass will be conducive to its usage in optical amplifiers and microchip lasers.

Preparation and Fluorescent Property of Eu-Doped High Silica Glasses

A method to fabricate europium ions doped-high silica glass for transparent fluorescence materials based on the fabrication and sintering technique of nano-porous silica glass was reported. Glasses impregnated with Eu ions and sintered at above 1150 °C in a reduction atmosphere show a very strong blue light from an emission band at about 430 nm due to the 4f65d→4f7(8S7/2) transition of the Eu2+ ions. On the other hand, the Eu-doped glass obtained by co-impregnated with Y3+ and V5+ ions and sintering in oxidation atmosphere behaves a very strong red emission band at about 615 nm with a UV excitation. An appearance of vanadate band in the excitation spectrum of Eu3+, Y3+ and V5+ ions co-doped high silica glass implies an effective energy transferring from VO43- to Eu3+ and effective excitation of Eu3+ by about 500 nm strong broad emission of VO43-.

Immobilization of simulated radioactivefluoride waste in phosphate glass

Radioactive alkali fluoride salts are generated during the operation of molten salt reactors (MSRs) and reprocessing of their spent fuel, and appear in the formof fluidity granule, or powder. In order to prevent the radionuclides from being released into the environment (especially, via exposure to water), it is necessary to develop a new technology for the temporary storage or final disposal of wastes containing radioactive fluorides. The immobilization of alkali fluoride wastes in phosphate glasses has been proposed. In this study, iron phosphate (IP) glasses and sodium aluminophosphate (NaAlP) glasses were evaluated for the immobilization of simulated radioactive fluoride wastes. IP and NaAlP glass matrixes were mixed with simulated wastes and reacted in air at temperatures in the range of 950–1200°C. A high waste loading was obtained in the experiment. The properties of the waste forms were characterized by X-ray diffraction and Raman spectroscopy. The latter indicated that IP glass contains less Q2 without Q3 (2 and 3 represent the number of bridging oxygens on a PO4 tetrahedron), and it is concluded that IP glass is more stable than NaAlP glass. Leaching tests were performed in deionized water by using the product consistency test A (PCT-A method), and the result shows that the leaching resistance of IP waste forms is better than that of NaAlP waste forms. This study demonstrates the potential of IP glass for the stabilization and immobilization of radioactive fluoride wastes from MSRs.摘要熔盐堆的运行和乏燃料的处理都不可避免地产生放射性氟化物废物.不同于传统堆产生的氧化物废物, 这些氟化物废物大多以颗粒、粉末等分散形式存在,且具有腐蚀、化学稳定性差、易潮解等特点, 所以其处理处置有赖于新技术新工艺的研究.本文分别选取铁磷酸盐(IP)玻璃和钠铝磷酸盐(NaAlP)玻璃固化模拟碱金属氟化物, 并用X射线衍射分析、拉曼光谱和产品一致性检验方法对其结构和抗浸出性进行了测试.实验表明模拟氟化物在两种玻璃中的溶解度都很高(40 mol%以上),NaAlP玻璃固化体中碱金属浸出率较高,这和其玻璃基材含有较多的Na有关,且拉曼光谱显示其结构中的磷氧四面体含有不稳定的Q3单元, 而IP玻璃固化体对所有元素的浸出率都低于1 g m−2 day−1,故对固化熔盐堆产生的碱金属氟化盐有很大的潜在研究价值.