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TiO2 films were prepared by laser chemical vapor deposition using Nd: YAG laser. Effect of precursor vaporization temperature (Tvap) and deposition temperature (Tdep) on microstructure and deposition rate was investigated. Single-phase anatase TiO2 films were obtained at Tvap = 453 K and Tdep = 1010-1080 K, whereas single-phase rutile TiO2 films were obtained at Tdep = 750-1180 K. TiO2 films showed a columnar growth and the diameter of columnar increasing with increasing Tvap from 453 to 623K. Morphology of TiO2 films changed from granular grains to polygonal grains, and then to terraced grains with increasing Tdep. At Tdep = 1000-1100 K, the deposition rate (Rdep) increased significantly from 25 to 980 um/h with increasing Tvap from 453 to 623 K. The highest deposition rate for TiO2 film reached 980 um/h at Tvap = 623 K and Tdep = 1068 K.

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Monolithic iron (III)-based gels with well-defined macropores have been synthesized from ionic precursors via sol-gel process accompanied by phase separation in the presence of propylene oxide (PO) and poly(acrylamide) (PAAm). Propylene oxide acts as an irreversible proton scavenger to induce homogeneous gelation, on the other hand PAAm as a phase separation inducer as well as a precipitation inhibitor. Appropriate choice of the starting composition allowed the production of co-continuous macroporous structure in a monolithic form. Dried gels were amorphous, whereas calcination under an inert condition led the formation of Fe₃O₄, iron, and/or Fe₃C at varied temperatures.

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Hydrotalcite-like compounds (HTlc) are a large class of layered double hydroxides and have been extensively studied. The synthetic HTlc are obtained as micrometer-sized crystalline powders generally. In the case of powders, however, a number of available active reaction sites are limited in the crystal surface because the diffusion of molecules in interlayer space is extremely slow. On the other hand, HTlc with meso and/or macrochannels is expected to facilitate the diffusion of guest molecules and lead to improve intercalation and release characteristics. In the present study, we synthesized HTlc monoliths with well-defined macrochannels via sol-gel reaction from metal salt precursors.

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Several monolithic porous materials have been developed through polymerization of molecular precursors in liquid media by adequately controlling the polymerization behavior and phase separation. New transparent and low-density methylsilsesquioxane aerogels, in particular, show unusual flexibility against compression, which allows evaporative drying to obtain aerogel-like xerogels under ambient conditions. Macroporous titania monoliths are prepared in mild conditions by controlling the reactivity of titanium(IV) alkoxide with chelating agent and catalytic amount of mineral salt. Macroporous organic crosslinked polymers are successfully obtained from multi-vinyl precursors by controlled/living radical polymerization, and further processed into monolithic activated carbons. Several possible applications of obtained materials will also be discussed.

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Surface modification of titania materials with flower-like structure has been achieved simply by the treatment in lithium hydroxide aqueous solution under mild conditions. The flower-like structured materials were characterized. The analyses results indicate that the flower-like materials are composed of layered hydrous lithium titanate. It is suggested that the unique intercalation behavior of lithium ions into titania allows dissolution and re-precipitation of titania to form the flower-like structure. The obtained flower-like structure can be retained up to 700 ºC, while the crystal phase transforms into Li₄Ti₅O₁₂.

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Oxygen-deficient titanium oxides (Ti_nO_2n-1) have attracted a lot of attention especially in electronics area due to their superior conductivity and chemical stability. In this study, monolithic Ti_nO_2n-1 materials with well-defined macropores have been synthesized from titanium hybrid gels which were prepared from titanium alkoxide and ethylenediamine via a nonaqueous so-gel reaction accompanied by phase separation. After the calcination in an inert atmosphere, macroporous Ti_nO_2n-1 materials were successfully obtained.

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Anti-reflection (AR) coatings are indispensable for reducing of incident light and eliminating the ghost and flare phenomena. In this work, alternative layer-by-layer assembled films were prepared using mesoporous silica nanoparticles (NPs) and polyelectrolytes which have opposite surface charge. The film thickness can be controlled by layer number, concentration of mesoporous silica NP dispersion, ionic strength of dispersions, etc. The obtained films have super-low refractive index and show a good AR property.

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I have found a variety of new inorganic compounds by hydrothermal reaction and determined their crystal structures. They are divided into three groups; i) transition metal oxides, ii) zirconium phosphates and iii) bismuth oxides. We will represent synthesis, crystal structure and some properties of those new inorganic compounds.

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(Na,K)NbO3(NKN) films have been synthesized at 240oC on SUS316 substrates by a hydrothermal method. The starting chemicals were fixed to NaOH and Nb2O5 for the Na and Nb sources, respectively. On the other hand, the K source was selected from three different chemicals of KOH, K2CO3 or their mixtures. In this study, the effect of K2CO3 content in the starting chemicals on the crystallinity, microstructure, and chemical stoichiometry of the grown film was investigated. It was found that the carbonate source could affect the solution-precipitation mechanism for the growth of NKN film during the hydrothermal reaction.

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We reported the eight-coordinated SrO synthesis on a magnesia plate using elemental diffusion. In this study, the blue luminescence of SrO:Eu²⁺ phosphor in water synthesized on single crystalline magnesia was investigated. The SrO:Eu²⁺ phosphor exhibited blue strong luminescence excited by 325 nm He-Cd laser during 7 days in water. 30 days after in water, luminescence of the sample changed to the weak emissions of 400 and 456 nm. These results indicated that the obtained SrO:Eu²⁺ phosphor presented high chemical stability under water compared with normal six-coordinated SrO.

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Tm³⁺ ion emit blue up-conversion light by three times energy transfer from other rare earth ion as a sensitizer. In this paper, we synthesized Tm³⁺/Yb³⁺-codoped TeO₂-TlO_0.5-ZnO glasses by quenching method, and estimated their blue up-conversion emission properties to find optimal glass composition. We found that optimal ratio Tm³⁺:Yb³⁺ is 1:5, but more Tm³⁺ ion is needed in the case of short melting time because of segregating.

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Mixed metal nitrides, M2Si5N8:Ce3+ (M = Ca, Sr, Ba), were synthesized from appropriate mixtures of MSi, Si3N4 and CeF3, by direct nitriding process in N2 gas : 2 MSi + Si3N4 + CeF3  M2Si5N8:Ce3+. Also, charge-compensated materials, M,2AlzSi5-zN8:Ce3+, were prepared from appropriate mixtures of MSi, MAlSi, Si3N4 and CeF3, and the luminescence properties were characterized. The resultant phosphors showed green emissions peaking at 489-528 nm, which are suitable for LED illumination by optimizing the mixing ratios of metal elements.

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A post flux treatment was carried out for Ba₃Si₆O₁₂N₂ doped with Eu²⁺ synthesized by an aqueous solution method. After the flux treatment, impurity phases of BaSi₂O₅ and Ba₃Si₆O₉N₄ were eliminated, resulting in the formation of a highly crystalline Ba₃Si₆O₁₂N₂:Eu²⁺ phase. The emission peak intensity of the sample after the flux treatment was ca. 3.1 times greater than that of the sample before the flux treatment.

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Anisotropic alkali meta-phosphate glass fibers were prepared with a fiber elongating method. Composition dependence of birefringence caused by the anisotropic structure was revealed that the phosphorus chain orientation in the fiber was predominantly affected by the kind of network modifier. LiNaKCsPO3 glass showed the highest birefringence among the alkali meta-phosphate glasses investigated in this study. The composition dependence of birefringence and mixed alkali effect were discussed in terms of the structural studies of the anisotropic glass fiber performed by the polarized Raman spectroscopy.

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A transparent SiO₂ body was prepared by spark plasma sintering (SPS), and the effects of sintering and annealing temperature on the transmittance of the SiO₂ body were investigated. The SiO₂ bodies sintered at 1073 to 1673 K were in amorphous state. The relative density of the SiO₂ body was 98% at 1373 K and reached 100% at 1573 K. The transmittance of the SiO₂ body sintered at 1573 K had the maximum values, i.e., 91% at a wavelength of 5000 cm^-1, 98% of the theoretical transmittance. In the ultraviolet range, the transmittance of the SiO₂ body sintered at 1573 K was about 40% at 200 nm. After annealing at 1073 K for 1 h, the transmittance in the UV range was increased to 75% at 200 nm, 82% of the theoretical transmittance.

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In order to fabricate graded-index optical elements with high quality through a staining method, it is important to investigate the behaviors of ion incorporation into glasses. Here, we carried out the silver-staining for aluminoborosilicate glasses with different fraction of non-bridging oxygen. The diffusion depth of silver was approximately 80μm for the staining at 300 C^o for 12 hours. This value was much deeper than that for a soda-lime silicate glass. The refractive index increased with 0.02 by the staining at 300 C^o for 3 to 6 hours.

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Halides have been incorporated into chalcogenide glasses for improving properties of these glasses. Here, we report a systematic research on properties of glasses based on GeS₂-Sb₂S₃-CsX (X=Cl, Br, I), in which cesium halides are substituted for GeS₂ of 60GeS₂-40SbS_3/2 glasses. Glasses were obtained until 25 mol% substitution of CsCl, and 30 mol% substitution of CsI for GeS₂. Glass transition temperatures of the GeS₂-Sb₂S₃-CsX (X=Cl, I) glasses lowered monotonically with increasing CsX content. Densities increased monotonically with increasing CsX content. We also measured variations in optical properties such as absorption edges and refractive indices.

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