| Research Abstract |
The influence of YF_3 and BeF_2 on vacuum ultraviolet (VUV) transmission spectra and refractive indexes of aluminum fluoroberyllate glasses was investigated. The MgF_2-CaF_2-SrF_2-AlF_3 containing 20 mol % BeF_2 glass composition exhibited the shortest wavelength of UV absorption edge (〜147 nm), and the highest transmittance at 157 nm (60 % for 2 mm sample thickness). In order to predict for the refractive indexes of fluoride glasses, we presented compositional parameter of fluoride based on our measured data.
Extended X-ray absorption fine structure (EXAFS) measurements have been performed on Er^<3+> and Yb^<3+> in oxide glasses in order to investigate the local structure surrounding Er^<3+> and Yb^<3+>. We classified the local structures surrounding rare earth ions in oxide glasses into two types : the former and the latter are interstitial and substitutive types, respectively. The relationship between the spontaneous emission probability for Er^<+3> : I_<13/2> →^4I_<15/2> and Yb^<3+>
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: ^2F_<5/2> →^2F_<7/2> transitions and their local structures in oxide glasses is discussed in terms of these two types.
The mechanical and thermal properties of oxide glasses were investigated. To predict the Young's moduli of the oxide glasses, empirical compositional parameters G_i and V_i were obtained, where G_i is the dissociation energy and V_i the packing density parameters of single-component oxide. Taking the network structures of phosphate and tellurite glasses into account, the G_i were modified. The results revealed that the calculated values using our proposed parameter were in good agreement with measured values all through the oxide glasses. The relationship between heat capacity and chemical composition was discussed in terms of the Debye model. We found that heat capacities of all the samples studied here scaled with the molar heat capacity at the Debye temperature have a similar magnitude and temperature dependence. Based on this observation, we propose an empirical equation which is composed of separate contributions of the compositional and temperature dependence of the heat capacity.
Phosphate glasses containing metallic copper nanoparticles were prepared by melt-quenching and post heat treatment method. The time-temperature-deposition (TTD) diagram for the glass dispersed with metallic copper nanoparticles was constructed based on the particle size and dispersion of metallic copper nanoparticles in phosphate glasses. A large amount of mono-dispersed metallic copper nanoparticles with a narrow size-distribution deposited in the 50BaO-50P_2O_5+6Cu_2O+6SnO+2Sb_2O_3 (mol %) glass samples heated below the glass transition temperature. In order to control the size, size-distribution, concentration, and dispersion of metallic copper nanoparticles in the glass, we discussed their deposition and growth mechanisms in terms of the redox reactions between Cu^+ ions and reducing oxides, i.e. SnO and Sb_2O_3, and the distribution of Cu^+, Sn^<2+>, and Sb^<3+> ions. Less
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