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The leaching behavior and structure of magnesium phosphate glasses containing 45-55 mol% MgO incorporated with simulated high-level nuclear waste (HLW) were studied. The gross leach rate of the glass waste form containing 50 mol% MgO and 45 mass% simulated HLW is of the order of 10^-6 g/cm²∙day at 90˚C, which is small enough as compared with the corresponding release from a currently used borosilicate glass waste form. The isolated ions such as dimeric (P₂O₇)^4- and monomeric (PO₄)^3- increase as increasing the incorporating amount of the simulated HLW. The changes in properties can be attributed to the structure changes owing to the incorporation of the simulated HLW.

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Beta-dicalcium silicate (beta-C2S) is an important constituent of cement and cement-based materials which are friendly to the enviroment. Hydration of beta-C2S was carried out under hydrothermal conditions at different temperatures from 50oC to 400oC up to 5 days by using two methods to start the hydration reactions at room temperature or at a desired reaction temperature. 7 kinds of hydration products of calcium silicate hydrates (C-S-Hs) were formed from beta-C2S. The stability and formation mechanism of the C-S-H phases were discussed. The effect of two reaction methods on formation of C-S-H phases was also investigated.

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Defect structures in ZnO were experimentally investigated by synthesizing ZnO doped with typical impurities and characterizing their optical properties. One of the obvious results found in the present study were lowering of the excitation threshold for optically pumped stimulated emission drastically decreased after introducing electrons into ZnO. Namely, addition of impurity to form shallow donor level improved luminescence efficiency of ZnO, and the some sort of defect causing reduction of luminescence efficiency can be passivated by addition of impurities causing shallow donors. From these experimental results, we will propose a model for the defect structures in ZnO reducing luminescence efficiency.

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I successfully prepared EuO and EuS nanocrystals. The EuO and EuS nanocrystals exhibited remarkable photophysical properties; strong photo-luminescence, special photo-magnetic behavior and large Faraday effect at room temperature. The EuO and EuS nanocrystals would lead to new materials for optical fiber and future photo-magnetic devices.

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Perovskite-related Ruddlesden-Popper-type compounds, A₃Ti₂O₇ : Pr³⁺ (A =Sr, Ca) were prepared by a Pechini-type polymerizable complex method using a citric metal complex or conventional solid state reaction, and their photoluminescence properties were investigated. The photoluminescence spectra have distinct peaks in the vicinity of 490 nm and/or 610 nm, which correspond to the intra-4f transitions of Pr³⁺. The excitation process is consistent with the transition between the valence band and the conduction band in host materials. Ca₃Ti₂O₇ : Pr³⁺ exhibits red emission more than ten times stronger than Sr₃Ti₂O₇ : Pr³⁺. The differences in luminescent properties among the compounds are originated from the structure dependence of the energy transfer from host to activator Pr³⁺, and the site symmetry of Pr³⁺.

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We have recently developed novel oxynitride phosphors based on alpha-SiAlON for white light-emitting didoes. The luminescence efficieny of these phosphors is greatly affected by the particle surface state, morphology and size distribution. To achive this goal, several strategies are employed, which include oxidation of phosphors, annealing, and careful selection of starting powders. This investigation reports that the luminescence efficieny of SiAlON phosphors can be improved by modifying the particle surface and by controlling the morphology and size distribution of phosphor particles.

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Silica film containing polarized molecules were prepared with sol-gel method. The molecules were aligned with electric field during gel formation. The molecules were removed with heat and a membrane with aligned pore was formed.

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Self-assembled pattern films prepared by sol-gel spin-coating method are evaluated. We found CeO2-TiO2 films have some unique pattern we had never seen before. Compared to other compositions such as SiO2, TiO2 or SiO2-TiO2 films that have simple stripe pattern, this film shows a complicated stripe pattern. To understand the reason why CeO2-TiO2 films have such a pattern, the surface pattern of CeO2-TiO2 and TiO2 films were observed by optical microscope and compared the results.

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Although the femtosecond laser induced waveguide or void formation inside a glass has been widely used for fabricating various micro-optics, the mechanism of the structural change has not been clearly understood. In this study, the dynamics of the structural change has been elucidated by observing the temporal evolution of the refractive index distribution with picosecond time resolution. We have observed the temperature increasing immediately after laser irradiation and the following thermoelastic relaxation process. The thermoelastic relaxation was accompanied with the generation and propagation of the shock wave. We consider that the shock wave is important for fabricating precise structures by laser irradiation.

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Copper bromide nanoparticles were precipitated in a bromide ion-containing borosilicate glass by copper-staining process. The average size of the CuBr nanoparticles was estimated by means of the exciton peak position of CuBr in an absorption spectrum. The change in the absorption bands of the CuBr exciton along the depth from the glass surface was observed by the measurement of the spectra after the glass polished step by step for 3 to 5 micron. It was found that the amount of CuBr was maximal around 20 to 30 micron in depth. The size of the particles gradually decreased from the surface to about 30 micron and after that rapidly decreased to 60 micron. The depth distribution of CuBr nanoparticles was directly observed by TEM.

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Binding energy of Ag of the sample sintered at 800C was lower than those of the samples sintered at other temperature. As well known, binding energy of oxidized Ag is about 0.4eV low than that of Ag metal. Therefore, decrease of binding energy of the sample which sintered at 800C means Ag metal was partially oxidized in this sample. It is considered that solubility of oxidized Ag to glass phase is much higher than that of metal. Solved Ag will be re-precipitated as metallic fine particles at the sintering temperature of more than 800C. Also, precipitated fine Ag particles will be acted as nucleation agent.

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Temperature dependence of binding energy of Li2O.2B2O3 glass containing 10wt% TiO2 were observed with XPS. Ti binding energy of the sample was monotonously increased with increasing temperature up to 500C, slightly decreased from 500C up to 600C, then increased again. Temperature of change in binding energy was almost consisted with crystallization temperature which estimated from DSC curve. Difference of binding energy between 500C and 600C was about 0.3eV and it was relatively small. Binding energy change is based on environment change of TiO6 unit from glass state to crystalline state was considered.

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Local structure of melt-quenched SnO-MxOy (M=B and P) glasses was analyzed by using solid-state NMR, Raman and Mossbauer measurements. Electrochemical properties during Li⁺ insertion and extraction of the glassy electrodes were investigated. Li⁺ insertion to the glasses brought about the reduction of Sn²⁺ and then the formation of nanocomposites with Sn nanoparticles in the Li₂O-MxOy matrix. Effects of local structure of the glassy matrix on the electrochemical performance of the SnO-MxOy electrodes are discussed.

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Thermodynamics of decomposition reaction of Na₂SO₄ in Na₂O-SiO₂ glass melts was investigated at 1350oC by the measurement of decomposition pressure. Decomposition pressure was reduced with the increase of Na₂O content because Na2O was generated by the decomposition of Na₂SO₄. The activity coefficient of Na₂SO₄ increased with the increase of Na₂O content.

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