The mullite/(0-40mass%) YPO₄ composites were mixed by wet ball-milling for 24h and sintered at 1550°C or 1600°C for 3h in air. The XRD patterns of sintered specimens show only mullite and YPO₄ peaks. The relative density of these specimens was over 95%. The composite containing 40mass% YPO₄ can be drilled and cut easily using conventional tungsten carbide metal-working tools. The 3-point bending strength of this specimen was 235.5 MPa.

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Preparation of ZrSiO₄/LaPO₄ composites and its mechanical properties were studied. ZrSiO₄ powder was mixed with highly sinterable LaPO₄ powder by a wet precipitation method. The powder was pressed and sintered at 1550°C for 3hr. The XRD pattern of body sintered showed that two phases didn't react and decomposite. The relative density of ZrSiO₄/LaPO₄ composites was around 96 %. The more we added LaPO₄ to ZrSiO₄, the more fast drilling rate was. Thus we succeeded to prepare machinable ZrSiO₄/LaPO₄ composites.

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Aluminium Titanate (AT) has micro cracks due to thermal expansion anisotropy in the sintered bodies. In the cause of micro cracks, AT has low strength, low thermal expansion and machinability. In this study, it is purpose to improve strength of AT with machinability keeping. To increase strength of AT, we added 10-40mass% mullite, middle thermal expansion, to AT. We discussed these specimens in three point bending test and drilling test.

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TiO₂ have many attractive properties. But, it is difficult to drill or cut because of their brittleness. The purpose of this study is to fabricate TiO₂/LaPO₄ composites which is high density and machinable, and to investigate the properties of them. Relative density of composites is above 95% by sintering above 1200°C. As LaPO₄ add to TiO₂, the speed of drilling TiO₂/LaPO₄ composites is faster. They can be drilled or cut with conventional metalworking equipment.

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The alumina of a particle was mixed to nickel-spinel. And the Al₂O₃nickel composites were prepared for it by the decomposition sintering process.In this study,the mechanical properties were measured.Three-point bending experiments showed an increase in strength for the nickel-reinforced alumina. The fracture strength was in excess of 490MPa.

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A laser dressed grinding stone (GS) possesses higher grains and more uniform grain distribution with respect to depth than a mechanically dressed GS. The matrix surface of a laser dressed GS is roughened by laser emission. Laser dressed surface topography gives a higher removed volume rate as well as lower specific grinding energy in constant pressure grinding at high pressure than a mechanically dressed surface.

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Influence of machining process on damage was examined with industrial alumina ceramics with several microstructures. Alumina ceramics were prepared by dry-pressing method with spray-drying granules. Changing sintering conditions developed several microstructures. The damage for machining process was changed by crystalline size and internal pore of alumina ceramics. After formed and sintered, characteristics of alumina ceramics were evaluated for grain size, internal pore size and porosity using several methods. The strength of ground ceramics was measured by a four point bending test. The damage in ground ceramics was studied by SEM and Laser scanning microscope.

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Single crystals of scandium oxide were synthesized electrochemically with applying the Sc3+ ion conducting Sc2(MoO4)3 solid electrolyte at 1223 K. Generally, single crystal growth of such refractory oxides as Sc2O3 is considerably difficult by the conventional thermal heating-cooling crystal growth procedure, because the melting point of Sc2O3 is as high as ca. 2773 K. The electrochemical method in this study can be simply applicable at moderate temperatures around 1273 K for the single crystal growth of refractory rare earth oxides by applying rare earth ion conducting Ln2(MoO4)3 solid electrolyte series.

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Transparent nonlinear fluoride single crystals of BaMF4 (M=Mg, Zn, Mn) were grown by the Czochralski technique with precise atmosphere control system, for all-solid-state VUV laser applications. These crystals showed short absorption edge down to 126 nm. Superior characteristics to generate 157 nm were observed.

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High-dense Ca-Ce-codoped α-sialon ceramics were prepared using the powder mixture of Si3N4-AlN-CeO2-CaCO3 system by gas-pressure sintering at 2000°C for 2 h. This material displayed photoluminesce.

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Solid solutions of EuxGd2-xMo5O18 were prepared by thermal decomposition of rare earth (=R) polyoxomolybdate [R2(H2O)12Mo8O27]ヮH2O, and their structures and spectroscopic properties were characterized. These materials exhibit bright red luminescence due to the 4f-4f transitions of Eu3+ under UV excitation. Vibronic transitions from 5D0 excited state coupling with Mo-O lattice vibrations were observed in the luminescence spectrum. A concentration quenching occurred at x>1.22. The luminescence intensity was c.a. one fourth of the commercially available phosphor Y2O2S:Eu3+.

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Photoluminescence properties of (Sr1-xCax)0.997Pr0.002TiO3 were investigated by excitation, emmition, and diffuse reflectance spectra in the range 300-800 nm at room temperature. The excitation spectra monitored at 613 nm and the diffuse reflectance spectra showed a two-step character due to valence-to-conduction band absorption and f2-fd absorption of Pr3+ ions. The valence-to-conduction band absorption and f2-fd absorption edges shifted to the high and the low wavelength side, respectively, as decreasing x. The mechanism of the emission of red light and the x dependence of intensity were discussed based on these results.

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Red long afterglow phosphor (Y0.9,Gd0.1)2O2S:Eu,Ti,Mg was synthesized by a gas absorption method. A single phase with red emission can be obtained by this method, and either Ti4+ or Mg2+ ion doping results in red long afterglow.

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Red emitting phosphor Y₂O₃:Eu was synthesized by gel combustion method. Small particle Y₂O₃:Eu (∼100 nm) was obtained although they agglomerated and formed a porous structure. The luminescence and XRD intensity showed a maximum when the glycine/nitrate ratio was 1.75, which corresponded to the high reaction temperature.

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We found that SnO2 nano crystals with a size of ∼5nm were precipitated by irradiating a femtosecond laser. The fluorescence from the Eu³⁺ ions codoped in glass was largely enhanced by the precipitation of SnO₂ crystals, in which the energy are efficiently transferred from the SnO2 into Eu³⁺ ions.

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β-BaB₂O₄(β-BBO) crystallines with second-order optical nonlinearity have been successfully fabricated at the surface of rare earth (Sm³⁺ and Dy³⁺) doped barium borate glasses by continuous irradiations of Nd:YAG laser. The induced crystalline phase was confirmed to be β-BBO in XRD measurements, and reratively strong second harmonic generation from the phase was clearly observed. In addition, we measured second harmonic waves by second harmonic microscope (SHM) and found the uniform intensity for whole length of the crystal lines.

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Room-temperature persistent holes are burned in frequency and wave-vector domains for multiple-scattering optical media based on Sm²⁺-doped glass powders. This phenomenon stems from three-dimensional random interference speckle patterns in disordered media. In our previous studies, we reported that the width of holes depends on the transport mean free path, the absorption length, and the sample thickness. In the present investigation, the effect of the polarization of incident light on the hole formation is demonstrated.

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Photochemical hole-burning of Eu-doped sodium borate glass is investigated as a function of doped ion concentration (0.1 and 0.3 mol%) and X-ray irradiation time (5, 10 min and longer) upon preparation. When the concentration is low, photochemical hole is formed only after X-ray irradiation. However, its stability against temperature is low. Therefore, contrary to reports in the literature, both defect centers created by X-ray and Eu2+ ion adjacent to a Eu3+ ion excited site selectively are responsible for the formation of photochemical hole with high temperature durability.

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Recently, we have successfully obtained highly Tb₂O₃-concentrated B₂O₃-Ga₂O₃-SiO₂-P₂O₅ glass, which exhibits excellent Faraday Rotation effect. In the present work, f-d transition energy of Tb³⁺ ions in the glass was investigated in excitation spectra, which was interpreted in correlation with results of Judd-Ofelt analysis of the glass.

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Nanometer-sized Au particles were dispersed in Eu3+-doped amorphous spheres (Au-ES particles) which were synthesized by sol-gel and ion-exchange method. Au nano-particles were obtained as a single crystal at room temperature. Reduction of HAuCl4 combined with oxidation of C2H5OH occurred to form Au nano-particles. Au nano-particles dispersed in Au-ES particles showed surface plasmon absorption.

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The porous glass was impregnated with rare earth ions, and then sintered at 1100°C. The fluorescent property of the rare earth ions contained in high silica glass was investigated. It was found that the Ce³⁺ and Eu²⁺ ions in the glass exhibit very strong luminescence. The kind of atmospheres during sintering influences the fluorescent property greatly.

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Emission properties at 1.5μm-band for Er3+-doped lanthano-silicate glass were investigated. Emission bandwidth of the glass is as broad as Bi2O3-based glass. Moreover, concentration quenching was not observed for the glass with the Er3+ concentration of 6000 ppm. Emission lifetime of 4|11/2 of the glass is about 20 μs, which is similar to that of silica glass. This means the glass has superior properties for application to broadband optical amplifier with high efficiency at 980 nm pumping.

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Utilization of phase separation phenomenon is one of the methods which can form interfaces in glass matrix in order to induce the light scattering. The purpose of this study is preparation of europium doped phase-separated alkaline earth silicate glasses, and the investigation of their fluorescence property. The phase separation texture was variously changed due to the composition of glass matrix. With increasing alkaline-earth content and ionic radius of alkaline-earth metal ion, the emission intensity of Eu3+ ion increased. It' s considered that fluorescence property of Eu3+ ion changes depending on phase separation texture.

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The lanthanide oxide phosphor (Y2O3:Eu3+) were incorporated into the pores of porous glass substrate by means of MOCVD method using lanthanide organic complexes. The resulting glass plate showed a large luminescent intensity compared with borosilicate glass doped with Eu3+ (1 wt%).

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SiO₂ glass for optical fiber is prepared from colloidal sol-gel process. The fumed silica is used for the preparation. The silica is dispersed in water containing with TMAH, surface-active agent and glycerin, and the ratio of the silica to water is 60-70 weight%. The sol solution is gelled immediately after addition of methyl formate, when the initial pH value of the sol is over 11. The gel is dried, refined in SOCl₂ and sintered at 1500°C in air or He atmosphere. In the case of the sintering process in He atmosphere, the silica sample hardly crystallizes.

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TiO₂ hybrid gel films were prepared from titanium butoxide chemically modified with 1,3-diphenyl-1,3-propanedione (DBM) and methacrylic acid by using sol-gel method. The absorption peak assigned to π-π* transition of β-diketonate chelate between Ti alkoxide and DBM decreased with the increase of UV irradiation time. By the structural change in UV irradiated parts on the film, solubility in alcohol differs from the UV irradiated to unirradiated parts. The TiO₂ film is exposed to interference light and the unexposed parts are removed, and then a two dimensional periodic structure is produced.

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Two-dimensional photonic crystals (PCs) consisting of a triangular array of titania rods with a lattice constant of 400 to 500nm were fabricated by sol-gel processing using polymer molds. In this synthesis, the use of electron beam lithography and dry-etching techniques was indispensable. The optical properties of the PCs were measured by a reflection method, and a distinct reflection peak in the visible region was observed. The wavelengths at which the reflection peaks appeared were confirmed to well agree with those theoretically predicted for the PCs.

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Silica gel films were prepared by spin-coating from Si (OC2H5)4-H20-HNO3-ROH solutions where ROH = CH30H, C2H50H, CH3OC2H40H or CH3CH (OH) CH20H, and were heated at 200°C. Surface roughness parameters, Ra and Rz, were measured on lines crossing vertically to the radiative striations on the film surface. Ra and Rz were found to be decreased with increasing boiling point of ROH. Just after the spin-coating, optical microscopic observation was made on a film prepared from the solution containing CH3CH(OH)CH2OH. Striations were detected initially, which diminished with time when the film was kept in the ambient atmosphere. This indicates that striations are formed even when ROH of high boiling points is used, which, however, diminish during drying when ROH is less volatile.

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Silica gel films were deposited on Si wafers by spin-coating using solutions of mole ratios, Si (OC2H5)4: H2O : HNO3: C2H5OH = 1 : x : 0.01: 4 (x=2, 4, 10). The gel films were heated at 10°C min-1, and in situ observation was made using an optical microscope. The cracking onset temperature was found to decrease with increasing H2O content in the starting solutions. The gel films were also heated at 5°C min-1 up to 500°C, and in situ measurement of stress in films were conducted using a thin film stress measurement instrument (FLX-2320, Tencor). In-plane intrinsic stress was tensile, increasing with increasing temperature, irrespective of the H2O content in the starting solutions, while larger stress was found in films prepared from solutions of higher H2O contents.

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Al₂O₃ gel films heated at 400°C were immersed in hot water at 100°C to give the flowerlike structure with a small roughness of about 50-80 nm on the surface. The thin film showed the anti-reflection property. The reflection of the f flowerlike Al₂O₃ film was less than 0.5% at wavelength region of 220-620nm. Further more at wavelength region of 270-320nm, the reflectance was less than 0.2%. Anti-reflection effect of the coating was improved by the control of the thickness of the films and the hot water treatment time.

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Inorganic-organic hybrid films from 2-(diethoxyphosphoryl) ethyltriethoxysilane (DPTS) and Na⁺-added SiO₂ films were prepared by the sol-gel method on glass substrates, and contact angles for water and oil droplets were evaluated in air and in water. Contact angle for water droplet in air on DPTS-based coating films was 60 degrees and for oleic acid droplet in water was 108 degrees. The addition of Na⁺ to SiO₂ was found to markedly improve the oleophobicity of the resultant films. The oleic acid droplet on the Na⁺-added SiO₂ films was spontaneously detached by immersion in water.

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Using heat-reduction method, we fabricated gold nanoparticles. And then, the particles were coated with silica whose shell thickness was controlled by tetramethoxysilane (TMOS). A hydroxylated glass substrate was dipped in a poly(diallyldimethylammoniumchloride)(PDDA) solution and then immersed into silica coated gold sol, which as a result was self-assembled on the glass.

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A large amount of H2O containing aluminosilicate glasses were prepared by the ion exchange of H+ for Li+, Na+ and Ag+ ions. All of Na+ and Ag+ ions in the glasses were leached out by dipping the samples in concentrated H2SO4 at 300°C for seven days, and the chemical analysis and the thermogravimetric analysis confirmed that H+/Na+ or Ag+ ion-exchange proceeded one by one in the glasses. H+/Li+ exchange also proceeded without crack, but a maximum ion-exchange ratio was 42% after the treatment for 3 weeks. The glass structures were investigated by infrared and Raman spectroscopies, and the relation with the glass properties was considered.

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Structure of silica nanotubes prepared from TEOS by sol-gel method using ammonium DL-tartrate as a template was examined by X-ray radial distribution function analysis. It was found that isolated silica nanotubes have a unit structure rather similar to silica glass. From the increase of intensity of IR absorption peak of Si-OH upon heated around 300°C in air, the formation of Si-O-C bonds between SiO₂ and the template was suggested.

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The phenomenon of phase separation in glass thin films has not been studied in detail. In order to investigate phase separation in films, 12Na20-88SiO2 films deposited on Si02 by RF magnetron sputtering method were prepared. Although they separated into two phases by heat treatment, the microstructure in the phase separation was different from that of the bulk Na2O-SiO2 system and was strongly influenced by the Na distribution along the depth ofthe films.

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Raman spectra have been measured for soda-lime silica glasses and melts at temperatures from 25°C to 1500°C, and the effect of alkaline-earth cation upon the structure was investigated. The temperature dependences of the Qn distribution in the melts were examined based on the reaction of 2Q3↔Q2+Q4. The standard reaction enthalpy ΔH of 16.7Na2O-16.7CaO-66.7SiO2 was 14kJ/mol, which was smaller than that of 33.3Na2O-66.7SiO2, 30kJ/mol.

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The structure of alkaline earth borosilicate glasses was investigated by using X ray photoelectron spectroscopy (XPS) and ¹¹B MAS NMR. In XPS, chemical shift of 01s signal was confirmed, and BaO- system showed larger shift than CaO- and SrO- systems. On the other hand, in 11B MAS NMR, the fraction of 4-fold B(N₄) showed no dependence on the sort of alkaline earth ions.

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¹¹³Cd magic-angle spinning (MAS)and static NMR spectra were measured of fourteen kinds of chlorocadmate glasses and eight kinds of chlorocadmate crystals with known structures to reveal the chlorine coordination environments around Cd²⁺ in the glasses in detail. At first the relationship between NMR parameters such as isotropic chemical shift δ_iso, chemical shift anisotropy Δδand asymmetry parameter θ and the chlorine coordination environments around Cd²⁺ in the crystals was established. Then the chlorine coordination environments around Cd²⁺ in the glasses were discussed based on the relationship found in the chlorocadmate crystals.

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The deformation of the soda lime silica glasses made by different cooling rate under pressure and stress were investigated by MD simulation. Two kinds of glasses were made by cooling from 3000 K to 300 K for 10 ps and 500 ps, respectively. Rapid cooling glass has the structure with more 3- and 4-membered rings and more dispersed distribution of modifier ions than that in slow cooling glass. Under pressure and stress, the deformed volume and strain of rapid cooling glass was larger than those of slow cooling glass. The difference of deformation between these glasses was due to the difference of network structure.

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The combinatorial glass research system has been developed. The Combinatorial Batch Preparation Apparatus can prepare the 24 different batches in the 4-component system within an hour. The Glass Formation Tester can manage 24 glass melting tests every 1 hour. The Combinatorial Glass Batch Melting Apparatus can deal about 100 batches a day during 9 hr operation. For the evaluation of the thermal stability of the glasses, the Combinatorial Glass Sample Melter and Annealer can prepare the conventional T-T-T curves quickly. The Combinatorial Glass Research System makes it possible to get several new glass systems together with some thermal data within a week.

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The transient nucleation was a process to change a cluster distribution to the equilibrium distribution at the nucleation temperature. DTA measurement was performed for Li2OSiO2 glasses with different thermal history in order to invest the effect of their cluster distribution. Crystallization peak temperatures were used as a measure of the number density of nuclei. The glasses heat-treated before nucleation showed lower crystallization peak temperatures. The induction time for steady state nucleation was considered to become shorter by the preliminary heat-treatment.

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Crystallization and resultant precipitated phases of 36.4(Ca_x(Sr_0.6Ba_0.4)_1-x)O·8.9Al₂O₃ 49.1SiO₂ 5.6Ta₂O₅(x=0-1.0/mol%) system glasses were investigated. Glass samples were prepared by conventional melt-quench method. Glass transition temperature Tg of samples of x=1-0.3 were about 800°C. However, Tg increased to 830°C with decreasing the value of x of samples. Major precipitated phases of sintered samples were CaTa₂O₆ phase and SrTa₄O₁₁ phase, and content of those depended on the value of x.

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Glass-forming region in the system ZrO2-WO3-Al203 was determined by melting and quenching method with Pt crucible, and thermal expansion of glasses was measured. The glass-forming region in ZrO2-WO3-Al2O3 system was found to be the vicinity of the composition of 20mol%ZrO20mol%WO30mol%Al2O3. In ZrW2O8-Al2(WO4)3 glasses, thermal expansion coefficient decreased slightly with increasing Al2(WO4)3 content.

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The chemical durability of Bi₂O₃ ternary glasses was measured by powder method (measuring method for chemical durability of optical glass). The glass powder was treated at 90C for 60 minutes in water. The chemical durability is the order of Li₂O>CaO=SrO>Na₂O>BaO. The electric field strength of cations is the order of Li₂O>CaO>SrO> BaO>Na₂O. It is apparent that the chemical durability corresponds with the electric field strength of cations. The reaction product was analyzed by XRD. The precipitate is only Bi₂O₃.

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Direct fabrication of ceramics from solutions has been developed in our group. Here we have developed another innovative process: Casting of multi-components melt to fabricate multi-phases ceramics nanocomposites. Near eutectic compositions in appropriate pseudo-ternary systems like ZrO₂ (or HfO₂)-Al₂O₃-ABO₃(perovskite) have been chosen. These samples were rapidly solidified after melting. They have given in-situ nanocomposites of three phases, or an amorphous bulk which can be changed into nanocrystalline bulk composites by appropriate annealing. Those methods should have huge potential in wide application areas.

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A commercial submicron α silicon nitride powder and aluminium powder were ground by planetary mill. The powder was sintered by spark plasma sintering.After the sintering, α silicon nitride and Y-α-sialon were detected.

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The deformation behavior of boron and carbon doped β-silicon carbide (B,C-SiC) with grain size of 260 nm was investigated by compression tests at elevated temperatures. Remarkable grain growth during deformation was observed. The stress-strain curves were corrected for grain growth. The stress exponent n was 1.3 and the grain size exponent p was 2.7. The apparent activation energy for deformation was 763 kJ/mol, which was lower than the activation energy of lattice diffusion of silicon and carbon. These results suggest that the dominant deformation mechanism of B,C-SiC is the grain boundary sliding which are rate-controlled by the grain boundary diffusion with a contribution of lattice diffusion.

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Nano-structured Si3N4 was consisted of the matrix grains with a size less than 100nm and nanometer size self-lubricant dispersions. The obtained material showed low friction coefficient and high wear resistance.

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Nanocomposites have received hot attention for the structural material in these ten years. In this study, Al₂O₃ / SiC nanocomposite was fabricated for the purpose of toughening and strengthening ceramic materials. Sub-micron sized α- or γ-alumina was used as starting material and nano-sized silicon carbide powder as second-phase particle. After wet boll milling, mixed powder was dried and sintered at 1350°C or 1450°C by SPS. Mechanical properties of fabricated samples and annealed one (1300°C in air) were measured. Fracture strength of annealed Al₂O₃ / 5 vol% SiC sample (prepared with α-alumina) and that of annealed Al₂O₃ / 3 vol% SiC sample (with γ-alumina) were 850 MPa and 845 MPa. And fracture toughness of Al₂O₃ / 3 vol% SiC sample (with γ-alumina) and that of annealed the sample were 4.7MPam^1/2 and 4.6MPam^1/2. Intragranular fracture was observed in these nanocomposites.

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