Abstract: Second harmonic generation (SHG) was observed from halide, in specific, chlorine or bromine-containing tellurite glasses. The magnitude of SHG increased with increasing halides concentration and poling time. Although the mechanism of SHG is still controversial, it is generally accepted that the idea of the deficiency of cations near the anode side cause SHG. However, in the preset oxyhalide glass system without any singly positive charge cation, the polishing of the anode side showed no effect on SHG. On the other hand, the polishing of the cathode side significantly decreased the magnitude of SHG in the present alkali-free oxyhalide glasses. Therefore, the SHG mechanism in the present oxyhalide glass systems is made evident in which the movement of anions results in an anion-deficient layer near the cathode side. (C) 2010 Elsevier B.V. All rights reserved.
Abstract: In this study an amorphous silica-alumina could be prepared using a carboxylic acid and its reactivity for the catalytic cracking was investigated. Malic acid (MA) was used as a catalyst for the sol-gel method, as an organic template and as a reagent for the dispersion of Al. When the ratio of MA/TEOS (tetraethoxysilane) increased from 0.22 to 1.22, the surface area, pore volume and pore diameter increased and the mesopore was formed at 1.22. The average BET pore diameters for 0.22 and 1.22 of MA/TEOS were 2.0-5.1 nm, respectively. With the single use of amorphous silica-alumina, conversions of n-dodecane were around 20% or less. With the single use of beta-zeolite, in contrast, the conversion to liquid and gas products reached 84%. In order to investigate the reactivity of amorphous silica-alumina as a matrix, we prepared the mixed catalysts which consist of 25% of zeolite, 56% of amorphous silica-alumina and 19% of binder (alumina sol) and we traced the activities for the catalytic cracking of n-dodecane. The average pore diameters were retained after zeolite was included. The product distribution changed compared with the single use of zeolite or silica-alumina and the comparable activity to that of zeolite was obtained although the mixed catalysts included only 25% of zeolite. Further, the amorphous silica-alumina with mesopores (MA122-5) exhibited the higher ratio of multi-branched paraffin to single branched paraffin in the gasoline franction of products (C5-C11) than the amorphous silica-alumina with only micropore or silica with mesopore or single zeolite. (C) 2010 Elsevier B.V. All rights reserved.
Abstract: Ti3+-free titanoborophosphate TiO2-B2O3-P2O5 (TBP)-based glasses were produced in order to obtain glasses with low T-g (<600 degrees C), high n(d) (> 1.8), and a short postannealing (PA) time (less than a few days). In addition, TBP- based glasses with low T-g (<570 degrees C), high n(d) (> 1.85), and a short PA time were successfully developed with the substitution of Li2O and ZnO for B2O3. Some glasses had very suitable properties for precision glass molding (T-g = 553 degrees C, n(d) = 1.851, PA time = 4 days for 6Li(2)O center dot 6ZnO center dot 55TiO(2)center dot 6B(2)O(3)center dot 27P(2)O(5) glass; T-g = 563 degrees C, n(d) = 1.880, PA time = 2 days for 5Li(2)O center dot 60TiO(2)center dot 10B(2)O(3)center dot 25P(2)O(5) glass; T-g = 566 degrees C, n(d) = 1.885, PA time = 3 days for 2.5Li(2)O center dot 2.5ZnO center dot 60TiO(2)center dot 10B(2)O(3)center dot 25P(2)O(5) glass; and T-g = 567 degrees C, n(d) = 1.890, PA time = 1 day for 5Li(2)O center dot 5ZnO center dot 60TiO(2)center dot 5B(2)O(3)center dot 25P(2)O(5) glass). The lambda(70%) of TBP-based glasses with n(d)>1.85 and commercially available molding glasses with n(d)>1.85 are 40-41 and 44-50, respectively, which means that these new glasses have even higher transparency in the visible region than those currently on the market. Thus, TBP-based glasses are considered to be promising materials as molding glasses with high transparency, low T-g, and high n(d).
Abstract: Aluminum oxide has been well known as the host matrix for the luminescent materials doped by luminescent centers such as Eu or Ce because of the low cost and the ease of forming. In this work, a fluorescent characteristic of the solid alumina was examined using low cost sol-gel technique. As a result, amorphous alumina sintered at 500 degrees C generated visible luminescence at similar to 430 nm, and that sintered at 700 degrees C showed visible luminescence at similar to 390 nm. (C)2008 The Ceramic society of Japan. All rights reserved.
Abstract: Second harmonic generation (SHG) was observed from external stress-applied silica glass. Since no SHG signal was obtained from stress-free silica glass, the SHG is considered to result from the strain caused by the externally stress. The intensity of SHG is about 0.1% of that of Y-cut quartz single crystal. The lost of centrosymmetry in the microstructure induced by external pressure seems to result in the SHG. (C) 2008 The Ceramic Society of Japan. All rights reserved.
Abstract: The reduction of mite allergen activities by photocatalytic treatment with titanium dioxide (TiO2) was investigated for a cleaner indoor environment. Degussa P25 TiO2 and recombinant Derf-1 protein were used as photocatalyst and mite allergen, respectively. Increasing amounts of photocatalyst gradually increased the rate of reduction of allergen activities. At the irradiation time of 60 min, the reduction rate of allergen activities was more than 96.9%, when more than 1 mg photocatalyst TiO2 was used. As a consequence, the photocatalytic treatment with TiO2 was very effective for the reduction of allergen activities. Since aspartic acid and glycine concentrations increased during the initial degradation, the destruction of amino acids may become a main reason for the reduction of allergen activities by low-cost photocatalytic treatment, which is simple and easy to handle.
Abstract: Ti3+-free multicomponent titanophosphate glasses were developed as ecologically sustainable optical glasses. Especially, recent advances in the glasses as molding glass, athermal glass, nonlinear optical glass, and self-cleaning glass were presented. The Ti3+-free binary TiO2-P2O5 glasses containing TiO2 up to 74 mol% were prepared by melt quenching and long-term post-annealing around the glass transition temperature in the air, and possessed high transparency, high index, high dispersion, and low density. Li2O-ZnO-TiO2-P2O5 glasses have the lowest T-g (=560 degrees C) among titanophosphate glasses, with high index (n(d)=1.8), and high dispersion (nu(d)=22) being retained, while ZnO-TiO2-P2O5 glasses have the highest refractive index (n(d)=1.9) among glasses with T-g lower than 600 degrees C. Thus, ZnO-TiO2-P2O5 and Li2O-ZnO-TiO2-P2O5 glasses can be expected as high-index molding glasses. A very small temperature coefficient of refractive index, dn/dT, or very small temperature coefficient of optical path length, dS/dT, was obtained for K2O-TiO2-P2O5 glasses, meaning that they are considered as high-index athermal glasses and athermal NLO glasses. Ag2O-TiO2-P2O5 glasses showed photocatalytic activity and photo-induced hydrophilicity comparable with commercially available TiO2-coated self-cleaning glasses.
Abstract: Silver particles generated by the evaporation-condensation method were deposited on the sol-gel derived silica film or the silica glass substrate to form SPR sensors, and their SPR sensing property was examined. When the sensing measurement was repeated. deposited silver particles gradually came off, and optical absorbance was decreased. To avoid these phenomena, silver particles were overcoated with silica thin film prepared by sonogel method. As a result. by adjusting the silica concentration of starting sol or the thickness of somo-silica overcoating, cycle performance of the sensor was improved. (c) 2005 Elsevier B.V. All rights reserved.
Abstract: CdSe nanocrystals were successfully embedded in high index glass films by rf-sputtering technique. All films showed the shift of absorption edge to shorter wavelength compared with that of bulk Use, so-called, blue shift, and it was evident that there is a quantum confinement effect in the films. The amount of the blue shift depended on the kind of matrix glass as well as the size of embedded CdSe nanocrystals. The third-order optical nonlinearity evaluated by Z-scan technique also depended on the matrix glass. The larger nonlinearity was observed from the matrix glass with higher refractive index. In addition, it was found that the value of shift of absorption edge, or the quantum confinement effect was linearly related to the third-order nonlinearity for CdSe nanocrystals embedded in glass thin films. © 2005 Elsevier B.V. All rights reserved.
Abstract: Second harmonic generation (SHG) was observed in heavy metal oxides glasses of PbO-Bi2O3-Ga2O3 glass system subjected to thermal poling treatment. There was a relaxation with time for the intensity of SHG for all of the present glasses. The intensity of SHG was very sensitive to poling temperature. A small addition of alkali oxides such as Na2O, increased SHG intensity, which is attributed to the increase of electric field (Ed,) in the glasses.
Abstract: Monolithic transparent and colorless, or Ti3+-free TiO2-P2O5 glasses containing very large amounts of TiO2 (up to 93 mol%) were successfully prepared by heat-treating the xerogels, which were made from titanium tetra-isopropoxide and triethyl phosphate, through the sol-gel reaction. The density and refractive index n(632.8 nm) of the sol-gel-derived glasses were higher than the melt-derived glasses of the corresponding compositions. The glasses of TiO2 content of larger than 80 mol% seemed somewhat porous, but n(632.8) of these glasses was very high as 2.2-2.3. Higher density and higher n(632.8 nm) than the melt-derived glasses were considered to be due to more abundance of six-fold coordinated Ti4+ ions. (C) 2004 Elsevier Ltd. All rights reserved.
Abstract: Second harmonic generation (SHG) was observed from halide, in particular, chlorine-containing glasses. The magnitude of SHG increased with increasing ZnCl2 concentration and poling time. Although the mechanism of SHG is still controversial, the deficiency of cations near the anode surface was detected. However, in this glass system, the polishing of the anode side showed no effect on SHG. However, the polishing of the cathode side significantly decreased the magnitude of SHG. Therefore, the SHG mechanism in this glass system is made evident for the first time in which the movement of anions resulting in an anion-deficient layer near the cathode side is able to cause SHG.
Abstract: Second harmonic generation was observed from thermally poled GeSx (x = 3, 4, 5, 6) glass system. The intensity of second harmonic generation depended on the S content. From x = 3 to 5, the generation increased with increasing S content, and then decreased at x = 6. There was apparent dependence of the second harmonic generation on poling temperature. The maxima appeared by poling at near glass transition temperature. By electron spin resonance and Raman scattering measurements before and after poling, it is evident that defects were formed by poling and the structure was deformed, which could relate to the generation. The relaxation of the generation was interpreted according to a recombination of defects and to a relaxation of structural deformation.
Abstract: Silver particles generated by the evaporation-condensation method were deposited to form a film on a silica glass substrate. The films thus obtained consist of nano-sized silver particles. Nonlinear refractive index, gamma and nonlinear absorption coefficient, beta determined by using Z-scan technique were both negative, while gamma in the literatures for the silver particles-dispersed-glass composites was positive. The absolute value of gamma for the as-deposited samples was increased as absorption peak wavelength due to surface plasmon resonance became close to the laser wavelength used in the measurement. The particle size (D) dependence, especially D-3 dependence of gamma was clearly observed for the films which were prepared at different particle generation temperatures and annealed at 170degreesC, and consisted of particles of 26 to 46 nm in size. This dependence was explained in terms of the quantum confinement effect.
Abstract: The 70TiO(2) (.) 30P(2)O(5) (mol%) glass was prepared by the sol-gel method. Its structure was examined by means of IR, Raman spectroscopy and X-ray radial distribution function analysis, and was compared with the corresponding melt-derived glass. It was found that average coordination number of Ti4+ ions was almost 6 and Ti4+ ions formed predominantly TiO6 octahedra in the sol-gel-derived glass, while Ti4+ ions were present in the 4, 5 and/or 6-fold coordination states to give average coordination number in-between 4 and 5 in the melt-glass. The preference of high coordination state of Ti4+ ions in the sol-gel glass was consistent with higher refractive index and density than the melt-glass.
Abstract: Various types of semiconductor microcrystal-doped glass thin films were successfully prepared by RF-sputtering. The blue shift of the absorption edge in the visible light region, caused by the quantum confinement effect, was observed in all the thin films. The amount of the blue shift was found to depend significantly not only on the types of semiconductor dopants and the microcrystal radius but also on the type of matrix. The blue shift of semiconductor microcrystals with a small exciton Bohr radius compared with the microcrystal radius, such as that of CuCl, showed an exciton confinement effect which was theoretically predicted. On the other hand, the blue shift of microcrystals with a large Bohr radius compared with the microcrystal radius, such as that of CdSe, has been expected to follow the electron-hole independent confinement model, but it was found to deviate significantly from the theoretical curve. In order to explain this deviation, we introduced factors, such as the Coulomb interaction between electron and hole, size-dependent dielectric constants of the dopants and the dielectric constant of matrix. Consequently, it was found that the matrices have a significant influence on the electron-hole independent confinement.
Abstract: The non-linear optical properties of Li2O-TiO2-P2O5 glasses were measured by Z-scan technique using a nanosecond pulsed laser. The non-linear refractive index (gamma(Z)) estimated from Z-scan normalized transmittance was considered to include the optical Kerr effect (gamma(K)), the thermo-optic effect (gamma(T)) and the resonant non-linearity (gamma(R)) related to Ti3+ ions of which content was increased with TiO2 content. The sign of gamma(Z) for glasses with 5 and 10 mol% TiO2 was positive, whereas for glasses with 15 and 20 mol% TiO2 it was negative. The YT of all the glasses in the present work was negative due to the negative temperature coefficient of linear refractive index (dn/dT), and decreased with increasing TiO2 content, and was considered to be dominated by the two-photon absorption. For Ti3+-containing 50Li(2)O - 15TiO(2).35P(2)O(5) glass with negative gamma(Z)(-1.78 x 10(-18) m(2) W-1), each of these three contributions was evaluated. The thermo-optic YT of the Ti3+-containing glass was determined to be -22.11 x 10(-18) m(2) W-1. Using the gamma(Z) and gamma(T) for the Ti3+-free glass made by remelting the Ti3+-containing glass at 1000 degreesC under O-2 atmosphere, the optical Kerr YK of the Ti3+-containing glass was found to be positive (11.87 x 10(-18) m(2) W-1). The resonant gamma(R) of the Ti3+-containing glass was found to be positive (8.46 x 10(-18) m(2) W-1). As a result, it was concluded that negative gamma(z) of the Ti3+-containing glass resulted from negative thermo-optic gamma(T). (C) 2003 Elsevier B.V. All rights reserved.
Abstract: Transparent glass-ceramics containing YAl3(BO3)(4) crystals were prepared by thermal poling of the Y2O3-Al2O3-B2O3 glasses. Second harmonic generation could be measured from both the glass-ceramics prepared with/without applied voltage, however, intensity is markedly enhanced in the samples prepared with applied voltage. In the thermally poled samples, the preferred orientation of precipitated YAl3(BO3)(4) crystals was observed, which may be attributed to the enhancement of second harmonic intensity.
Abstract: Electroluminescence was observed in CdSe microcrystal-doped indium tin oxide (ITO) thin films prepared by the Rf sputtering method. The size of CdSe microcrystals was changed by altering the relative surface area of the CdSe pellets on the ITO target. Emission spectra shifted from red to yellow with decreasing CdSe microcrystal size. The shift was considered to result from the blue shift of the absorption edge caused by the quantum confinement effect of CdSe microcrystals. Below the threshold voltage for the elctroluminescence phenomenon, the relationship between applied voltage and induced electric current was ohmic, and above the threshold voltage, electric cur-rent significantly increased. With respect to the color center, defects in CdSe microcrystals may play an important role in the EL process.
Abstract: Glass-ceramics containing feffoelectric CsLiB6O10 crystals were prepared by heat treating CS2O-Li2O-B2O3 glasses. Second harmonic generation (SHG) was observed from samples prepared by two-step heat treatment (nucleation and growth); however, the intensity was rather weak. On the other hand, one-step heat treatment by the addition of a small amount of TiO2 to the glass resulted in the glass-ceramics containing small single crystal-like CsLiB6O10 particles. The strongest SHG observed was comparable with that of Y-cut quartz. The preferred orientation of precipitated CsLiB6O10 crystals was attributed to the occurrence of SHG from the glass-ceramics.
Abstract: Alumina gels were prepared from aluminum-sec-butoxide by sol-gel method at OT using HNO3 as a catalyst. The crystallization behavior of the gel was compared with that of HCl-catalyzed alumina gels. alpha-Al2O3 did not form until 950degreesC in HNO3-catalyzed gels, while HCI-catalyzed one partially transformed to alpha-Al2O3 around 500degreesC. Corundum-seeding affected crystallization in a different way as compared to the HCl-catalyzed one, i.e., the alpha-transformation in the temperature range of 800 to 1000degreesC was better enhanced by seeding and was completed at 800degreesC when seeded to a level of 5 mass%. It was considered that NO3- ions assisted the building of a gel structure in which aluminum or oxide ions are readily diffused at temperatures higher than similar to800degreesC.
Abstract: CdSe microcrytsals with various sizes was successfully embedded in SiO2 glass matrix by magnetron rf-sputtering technique. The mean size of microcrystals was controllable by changing the relative surface area ratio of the CdSe chips to the matrix in the target, and increased with increasing the relative area. The negative real part of the third-order optical susceptibility was seen for all of the present films, and the magnitude of the absolute value of real part increased with increasing concentration of CdSe. The imaginary part due to two photon absorption also increased with the CdSe concentration. After normalized with respect to the concentration, it was revealed that actual optical third-order nonlinearity of the CdSe microcrystals increased as the mean size decreased, in other words as the quantum confinement effect increased.
Abstract: In order to evaluate the large third-order optical nonlinearity of materials accurately, the influence of the irradiance (I-0) and sample thickness (L) on the Z-scan transmittance of PbO-containing glass as a representative material was investigated using simple and conventional Z-scan experiments and analyses. The transmittance difference between the peak and valley (DeltaT(p-v)) in the Z-scan curve resulting from nonlinear refraction and the difference between the baseline (1.0) and valley (DeltaT(1-v)) due to nonlinear absorption deviated from a linear relationship at increased I-0 and L. It was found that an analysis based on the linear relationship at large I-0 and L underestimated the third-order optical nonlinearity due to saturation. Taking into consideration the saturation of DeltaT(p-v) and DeltaT(1-v) with L under moderate irradiance, the intrinsic nonlinear refractive index (gamma) and nonlinear absorption coefficient (beta) of the present glass were calculated to be 1.58x10(-17) m(2) W-1 and 7.75 cm GW(-1), respectively. (C) 2001 American Institute of Physics.
Abstract: The hydrolysis of aluminum-sec-butoxide (ASB) in the ASB-H2O-C2H5OH-HCl solutions at 0 degreesC for 18 h and subsequent aging of the sol for 30 days at 5 degreesC provided an alumina gel which was partially (20-30 wt%) transformed to alpha -Al2O3 when heat-treated at 500 degrees -600 degreesC under ambient pressure. In addition to the hydrolysis and aging conditions, the amounts of water and HCl in the starting solution were found to be very important factors for the low temperature formation of alpha -Al2O3 in the resultant gel. Some difference in the chemical environment of involved OH groups was found between the alumina gel forming alpha -Al2O3 at 500 degrees -600 degreesC and the conventional gel. Corundum seeding was found to be effective; thus, 1 wt% seeding brought about an increase in the fraction of alpha -Al2O3 formed at 600 degreesC to 40-50 wt%.
Abstract: The effect of thermal/electrical poling on the surface structure of 30ZnO . 70TeO(2) glass has been investigated by means of IR reflectance and X-ray photoelectron spectroscopy (XPS), All the poled glasses exhibit a common characteristic that the second-order nonlinearity is induced preferentially in an anode-side surface region. The reflectance from the anode-side glass surface at around 635 cm(-1) assignable to the vibrational mode of the Te-O-ax bond, where ax stands for the axial position of the TeO4 trigonal bipyramid, is smaller in comparison with both as-annealed and cathode-side surfaces. The XPS analysis of the anode-side surface shows a depletion of Zn2+ ions and penetration of Na+ ions from the borosilicate glass which was placed between the sample and the anode during poling, These results suggest that the poling brings about both the breaking of the tellurite glass network and compositional changes at the anode-side surface below which the second-order nonlinearity is preferentially induced.
Abstract: Second-harmonic generation (SHG) was observed from PbO-GeO2 glasses after thermal poling. As in PbO-SiO2 glasses, the compositional dependence of SHG intensity was found, although the SHG intensity was rather small. The largest SHG intensity was observed for about PbO = 35 mol%. On the basis of extended X-ray analysis fine structure (EXAFS) results previously obtained, it was considered that remarkable increase of SHG intensity found for PbO > 20 mol% was caused by the formation of non-bridging oxygens. On the other hand, then the decrease of the intensity at PbO > 35 mol% was due to the disappearance of non-bridging oxygens.
Abstract: The alkali borosilicate glasses containing CdS as a constituent were heat-treated or thermally poled to prepare CdS microcrystal-containing glasses, Second harmonic generation (SHG) from these glasses was measured, and the effects of the applied voltage on the crystallization behavior and SHG intensity were discussed. In poled glass samples, wurtzite type CdS microcrystals were precipitated at lower temperature than in unpoled ones. it was considered that the applied electric field affected the crystallization behavior of CdS crystals through the increase of temperature of the glass sample and migration of S2- ions. The poled sample showed larger SHG intensity than the sample merely heat-treated, which was explained in terms of modification structure and orientation of precipitated CdS microcrystals. (C) 2001 Elsevier Science B.V. All rights reserved.
Abstract: Second-harmonic generation (SHG) was observed from thermally poled alkaline earth containing mixed alkali silicate glasses. Since no SHG could be observed in alkaline-earth oxide-free glasses, it was considered that alkaline-earth oxide played a significant role in the generation. The intensity of SHG increased with the time and applied voltage of poling. However, no oscillation fringe pattern was observed even in the glasses poled most intensively in the present work, at 3 kV for 6h, which indicates that the poled layer is limited near the surface area and thinner than the coherent length. On the basis of IR reflection spectroscopy and electron probe microanalysis (EPMA) data, the SHG was related to the positive ion depletion immediately beneath the glass surface on the anode side. From the finding that the migration of cations or ion depiction on the anode side was larger in the glass containing layer alkaline-earth ions, it was considered that the large migration reduced the space charge gradient and resulted in a lower SHG intensity.
Abstract: The medium-range-network structure of silicas from different sources was comparatively examined by X-ray diffraction, IR and NMR analyses. Silica gels made through the conventional sol-gel route were found to have a different structure from silica glass, and considered to be composed of 4-fold siloxane ring units, irrespective of preparation conditions. Amorphous silicas in rice-hulls and bamboo leaves showed structure data close to silica glass, being suggested to consist mainly of 6-fold siloxane ring units. The modified sol-gel method, in which siloxane oligomers containing cyclic siloxane tetramers may have been ring-opened and polymerized under the catalytic reaction of NaOH or NH4F in the water-free solution, provided the silica gel of which structure was very similar to silica glass.
Abstract: CdSe microcrystals were successfully dispersed in GeO2 glass and CaF2 crystal thin films by rf-sputtering. All films prepared showed the blue shift of absorption edge in visible spectra due to quantum size effect. The amount of the blue shift of the films increased with decreasing the size of the microcrystals. Comparing the amount of the particle size-depending blue shift of CdSe microcrystals dispersed in between the GeO2, CaF2 and SiO2 matricies, the influence of the matrix on the shift was found. Therefore, it can be said that there is an influence of the matrix on the quantum size effect. From the modified theoretical calculation, the influence of matrix was considered to appear through Coulomb interaction between electrons and holes. (C) 2000 Kluwer Academic Publishers.
Abstract: The effect of addition of Na2S on the structure of Na2S-GeS2 sulphide glasses was investigated by XPS, IR, XRD and EXAFS measurements and discussed by comparison With that of Na2O an the structure of Na2O-GeO2 oxide glasses Unlike the change of coordination number of Ge atom from 4 to 6 in Na2O-GeO2 oxide glasses with addition of Na2O, in the case of Na2S-GeS2 sulphide glasses, the coordination number of the Ge atom with respect to sulphur remains 4. [GeS4] tetrahedron is the network forming unit and no occurrence of [GeS6] octahedron was observed in the Na2S-GeS2 glasses with addition of Na2S. The added Na2S is consumed in the formation of nonbridging sulphurs. The mechanism of the formation of nonbridging sulphurs and the structure of the Na2S-GeS2 glasses are modelled.
Abstract: The third-order optical nonlinearity of glasses of the Na2S-PbS-GeS2 and Na2S-PbO-GeS2 systems was measured by third harmonic generation method. The third-order nonlinearities of glasses of both systems increase with the increasing lead content. The maximum value of the third-order optical nonlinearity was 3.00 x 10(-12) esu. The addition of PbO basically has little influence on third-order optical nonlinearity, and the largest nonlinearity is 1.49 x 10(-12) esu. The minimum appearing at 15 mol % PbO can be explained by the decrease of number density of lead and sulfur. Chemical durability of oxysulfide glasses is superior to that of a pure sulfide system; thus the addition of PbO is important in this sense.
Abstract: The low temperature preparation of Fe-zircon pigment powders was conducted using the sol-gel method. The influence of firing atmosphere on the coloration and chemical durability of the pigment were examined, and the incorporation behavior of Fe ions into zircon matrix was discussed. The pigments were formed at lower temperature (900-1000 degrees C) than that in the conventional solid-state method, when LiCl was added as a mineralizer (or catalyst) instead of conventional, the complicated mixture of several mineralizers. It was found that a large part of Fe ions is included in the pigment as alpha-Fe2O3. Fe-zircon pigments showed higher acid-durability compared to the commercial one, suggesting that alpha-Fe2O3 is embedded in the zircon matrix as uniformly distributed minute particles.
Abstract: The non-linear refraction and non-linear absorption of melt-derived and sol gel-derived TiO2-containing glass samples were investigated by the Z-scan technique. Primarily, the effects of composition and structure of glasses on the non-linear refractive index (gamma) were measured. We found that a thermo-optic effect is present in the measurements of gamma at TiO2 content <25 mol%, and TiO2 component is the source of a positive Kerr effect at TiO2 content between 25 and 70 mol%, whereas it is the origin of a negative Kerr effect at TiO2 content >70 mol%. Consequently, we assumed that the sin inversion of gamma around 25 mol% TiO2 in melt-derived samples is due to the change of dominant factor of gamma from thermo-optic effect to Kerr effect, whereas the sign inversion of gamma around 70 mol% TiO2 in sol-gel-derived samples may be due to the wavelength dispersion of gamma. (C) 1999 Elsevier Science B.V. All rights reserved.
Abstract: Silicon oxycarbide (Si-O-C) glass fibers were prepared by heat-treating the gel fibers drawn from the solution containing tetra-ethyl-ortho-silicate (TEOS), tri-ethoxysilane (HTES) and methyl-tri-ethoxysilane (MTES) in the course of sol-gel reaction. The replacement of TEOS by HTES in the solution, with the molar ratio of MTES to total alkoxysilanes being kept constant at 1/3, resulted in remarkable improvement of tensile strength of the glass fibers prepared at 1300 degrees C. The decrease in the content of free carbon was observed in such fibers, even by an amount as small as a few wt%, and was considered to be related to the suppression of devitrification of the fibers to form beta-SiC and to the enhancement of mechanical strength.
Abstract: CuCl microcrystals-doped SiO2 glass thin films were successfully prepared by rf(radio frequency)-sputtering method. The formation of CuCl microcrystals in the glass thin films has been explored by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The quantum size effect in CuCl was found from the blue shift of exciton absortion peaks. Although some influence of the matrix on the temperature dependent linewidth of the exciton peaks was observed, the relationship between the amount of blue shift of the absorption edge and the diameter of the CuCl microcrystals satisfied the theory for the quantum-size confinement of the exciton.
Abstract: The two-photon absorption coefficient (beta) and nonlinear refractive index (gamma) of the binary La2S3-Ga2S3 and ternary MS-La2S3-Ga2S3 (MS=Ag2S and Na2S) glasses were measured at 532 nm by the Z-scan method. The beta of the glasses was similar to 40 cm GW(-1) and nearly unchanged with La2S3 content in the binary glasses, while it increased, or decreased with the substitution of Ag2S, or Na2S, respectively, for La2S3 in the ternary glasses. The gamma of the glasses increased, with the rising La2S3 content in the binary glasses, and increased, or decreased with the addition of Ag2S3 or Na2S, respectively, in the ternary glasses. The results were compared with the third-order nonlinear optical properties measured by third harmonic generation and discussed on the basis of their linear optical properties. (C) 1998 American Institute of Physics. [S0021-8979(98)05517-0].
Abstract: Silica gels made from tetra-ethyl-orthosilicate (TEOS) under the basic condition and one made by two-step hydrolysis were studied by X-ray radial distribution function and correlation function analyses, and Si-29 NMR. X-ray scattering intensity, the medium range feature of the radial distribution function (RDF) curve and correlation function curve of silica gels was different from those of melt-derived silica. No difference in X-ray data was noted among the gels. The X-ray RDF data of the silica gels prepared under the basic condition and by the two-step by hydrolysis method were explained by using a medium-range-order (MRO) structure model consisting of fourfold siloxane ring units instead of sixfold siloxane rings which prevail in the melt-derived silica glass. It was estimated that the primary particles of the acid-catalyzed silica gels built up by fourfold rings were around 1.0 nm in size, and those of the base-catalyzed silica gels were a little larger. 40-50% of silicon atoms in the primary particle in the acid-catalyzed gels, and 60-70% of silicon in the base-catalyzed gels were bonded to other particles through forming Si-O-Si bonds. The remaining silicon atoms were terminated by forming Si-OH bonds which were considered to stabilize the fourfold siloxane ring unit in the gels. (C) 1998 Elsevier Science B.V. All rights reserved.
Abstract: The set-gel method was applied to the preparation of zircon, ZrSiO4 powders. The addition of lithium ions to the ZrO2. SiO2 gels was found to be very effective to produce zircon at temperatures as low as 800-900 degrees C. The zircon formation process in the gels was followed by using X-ray diffraction and i.r. analysis methods. A possible mineralizing mechanism of lithium ions, which is essentially different from the previous ones for the solid-state reaction, was proposed. Namely, the formation of orthosilicate such as Li4SiO4 as an intermediate compound was considered to trigger the zircon formation at low heat-treatment temperatures. (C) 1998 Kluwer Academic Publishers.
Abstract: Perovskite La0.5Li0.5TiO3 (LLT) thin films, 0.2-1 mu m thick, were deposited on non-alkali aluminoborosilicate glass substrates (NA substrates) and glass substrates with ITO (indium tin oxide) coatings (ITO substrates) by the sol-gel method. Alkoxide-based solutions containing titanium alkoxide, lithium alkoxide and lanthanum alkoxide and acetate-based solutions containing titanium alkoxide, lithium acetate anti lanthanum acetate, were used as coating solutions. Impurity phases tended to be precipitated on heat treatment in the films derived from the acetate-based solutions. Addition of acetylacetone or partial substitution of lead for lithium in the acetate-based solutions, however, was effective in suppressing the precipitation of impurity phases. Preferred orientation of the LLT (111/2) plane was observed in the films prepared from the acetate-based solutions when NA substrates were used, whereas the employment of the alkoxide-based solutions or ITO substrates and the partial substitution of lead for lithium, I educed the preferred orientation. The electrical conductivity of the films was much lower than the values reported for the sintered materials.
Abstract: Second-harmonic generation (SHG) was observed in silicate glass containing Ga2O3 after electrical poling treatment. The SHG intensity was strongest at the poling temperature of 250 degrees C and for the glass compoition of 7.5Li(2)O . 7.5Cs(2)O . 25Ga(2)O(3) . 60SiO(2) (mol%). The second-order nonlinear coefficient d(33) was as large as similar to 13% of d(22) for LiNbO3.
Abstract: The third order nonlinear optical susceptibilities chi((3)) of BaO-TiO2-B2O3 glasses have been measured by the third harmonic generation (THG) method. Raman spectroscopic investigation revealed that Ti4+ ions mainly exist as 1-coordinated. It was found that the addition of TiO2 to BaO-B2O3 glass increases the chi((3)) as well as the refractive index, The positive effect of the TiO2 on the chi((3)) was interpreted in terms of the empty d-orbital contribution. The largest chi((3)) obtained is 3.0 x 10(-13) esu for 35BaO . 55TiO(2) . 10B(2)O(3) glass, which is, however, only 10 times larger than that for SiO2 glass. Such a small enhancement in chi((3)) is ascribed to the large fraction of 4-coordinated Ti4+ ions in BaO-TiO2-B2O3 glasses. It is concluded that, for TiO2-containing glasses, the higher chi((3)) values are attained when the optical basicity is low and the amount of Ti4+ ion is large. It was found that the modified Lines' relationship between chi((3)) and (n(omega)(2)+2)(3) .(n(omega)(2)-1). E-d/E-0(2) is adopted for this system.
Abstract: Third-order non-linear optical properties of Na2S-GeS2 glasses were measured by the third harmonic generation method. The chi((3)) of the glasses was of the order of 10(-12) esu, which is one order of magnitude larger than that of Na2O-GeO2 glasses. Unlike Na2O-GeO2 oxide glasses, the density, refractive index and chi((3)) value decrease upon addition of Na2S to GeS2 glass, which suggests no structural change from the [GeS4] unit to the [GeS6] unit. Structural studies by IR and XPS methods revealed the formation of non-bridging sulfur in the glasses. It was found that the contribution of non-bridging sulfurs to chi((3)) is larger than that of bridging sulfurs.
Abstract: The dependence of the third-order nonlinear optical properties of the La2S3-Ga2S3 and MS-La2S3-Ga2S3 (MS = PbS, Ag2S and Na2S) glasses on the composition, linear refractive index and optical band gap was examined. The chi((3)), Of the glasses was similar to 10(-12) esu, which was about 100 times as large as that of silica glass, and was increased with the increase of La2S3 content in the La2S3-Ga2S3 binary glasses, while it was increased with the substitution of PbS or Ag2S for La2S3 and decreased when La2S3 was replaced by Na2S. The chi((3)) of the glasses was found to increase with the increase of linear refractive index and the decrease of band gap, being in accordance with the empirical Miller's rule and optical band gap model.
Abstract: The third-order nonlinear optical properties of the sol-gel derived Pb(Fe1/2Nb1/2)O-3-PbTiO3 (PFN-PT) thin films have been investigated by the THG method. The chi((3)) values of PFN-PT thin films increased from 3.2 x 10(-12) esu (PT) to 8.5 x 10(-12) esu (PFN) with increasing content of Fe3+ ions which possessed very high second-hyperpolarizability, gamma(Fe2/3O). It was experimentally confirmed that complex oxides such as ABO(3)-type perovskites consisting of large non-transition metal A-site cations and small transition metal B-site cations exhibited high chi((3)) as expected from Lines' model. It was also found that the chi((3)) values of complex oxides could be estimated from the second-hyperpolarizabilities of the constituent single oxides reported so far. Because of the large remanent polarization, PT thin films may exhibit the highest chi((2)) among the ferroelectric PFN-PT thin films studied in the present work. The maximum dielectric constant, epsilon, of 1990 at room temperature was obtained for 0.5PFN.0.5PT thin films, whose composition corresponds to so-called morphotropic phase boundary (MPB).
Abstract: The third order nonlinear optical susceptibilities chi((3)) of Sb2O3-B2O3 binary glasses have been measured by the third harmonic generation (THG) method. The IR and Raman spectroscopic study reconfirmed that the structure of Sb2O3 glass is similar not to senarmontite but to valentinite which consists of double-chains of SbO3 units. The formation of BO4 units is much smaller for Sb2O3-B2O3 glasses than Bi2O3-B2O3 glasses at all compositions, which is ascribed to the covalent character of Sb-O bonds. It is also considered that Sb2O3 is present as SbO3 trigonal units and participates in the glass network formation through the Sb-O-B bonds. The chi((3)) value increased monotonically with increasing Sb2O3 content up to 8.4 x 10(-13) esu for Sb2O3 glass, which is about 30 times larger than SiO2 glass. Modified Lines' linear relationship between chi((3)) and (n(omega)(2) + 2)(3) .(n(omega)(2)-1). E(d)/E(0)(2) was adopted to Sb2O3-B2O3 glasses.
Abstract: Several transition metal oxide thin films have been prepared on SiO2 glass substrates by the sol-gel method and their nonlinear optical (NLO) properties have been examined on the basis of the third harmonic generation (THG) method. It was found that for transition metal oxides with empty d-orbitals the third order nonlinear optical susceptibility chi((3)) increases with decreasing M-O bondlength. This phenomenon was explicable in terms of Lines' bond orbital theory. On the other hand, iron oxides with partially filled d-orbitals exhibited quite high chi(3) Of the order of 10(-11)-10(-10) esu, which was considered to be due to the pair excitation process involving the simultaneous excitation of magnetically coupled two neighboring Fe3+ ions. Second hyperpolarizability gamma of various metal cations was estimated from our results, which is a measure of microscopic NLO properties of individual constitutional metal cations.
Abstract: Preferential c-axis orientation of LiTaO3 was observed in surface crystallized 35Li(2)O . 30Ta(2)O(5) . 35SiO(2) glass. Second harmonic generation (SHG) was observed in surface crystallized glass poled at room temperature for 24h under a 0.7kV dc voltage, whereas it mas not observed in an unpoled sample. The SHG observed in this study was attributed to residual polarization in LiTaO3. The d(33) value of the poled sample was estimated as 0.13 pm/V which was 0.5% of the das value for LiTaO3 single crystal.
Abstract: Phase matching for the third-harmonic generation (THG) of rutile single crystal (110) at 1.9 mu m has been investigated. THG with a visible red light (633 nm) was clearly observed, indicating that TiO2 (rutile) is one of the most promising third-order nonlinear optical materials. (C) 1996 American Institute of Physics.
Abstract: The third-order nonlinear optical properties of sol-gel derived alpha-Fe2O3, gamma-Fe2O3, and Fe3O4 thin films have been investigated by the third-harmonic generation method. Especially, the effects of the valence and coordination number of Fe ions on the third-order nonlinear optical susceptibility, chi((3)), have been examined. The chi((3)) values of alpha-Fe2O3, gamma-Fe2O3, and Fe3O4 thin films were 5.8X10(-11), 2.1X10(-11), and 4.0X10(-10) esu, respectively, which are the highest values among inorganic oxides reported so far. It was considered that chi((3)) of alpha-Fe2O3 and gamma-Fe2O3 was enhanced by the pair excitation process involving the simultaneous excitation of magnetically coupled two neighboring Fe3+ ions as well as by virtual transition from O 2p orbitals to Fe 3d orbitals while chi((3)) of Fe3O4 was enhanced by both one- and three-photon resonances. The higher second hyperpolarizability, gamma(Fex/yO), was obtained when Fe ions are 3+ rather than 2+ and octahedrally rather than tetrahedrally coordinated by oxygens. (C) 1996 American Institute of Physics.
Abstract: The third order nonlinear optical susceptibilities chi((3)) of AgX-Ag2O-B2O3(X=Cl, Br and I) glasses have been measured by the third harmonic generation(THG) method with special attention to highly polarisable cations and halide anions contained in these glasses. It was found that the chi((3)) of Ag2O-B2O3 and AgX-Ag2O-B2O3 (X=Cl, Br and I) increases with increasing content of Ag2O and AgX, respectively. The largest chi((3)) value obtained is 6.0x10(-12) esu for the 50AgI-25Ag(2)O-25B(2)O(3) ternary glass, which is about 200 times greater than that of silica glass. Such a large chi((3)) may be ascribed mainly to the optical resonance effect and the strong p-d mixing of silver halide as well as high polarisability of silver and halide ions. The modified Lines' linear relationship between chi((3)) and (n(omega)(2) +2)(3).(n(omega)(2) -1). E(d)/E(0)(2) was found to be adopted well for these glasses.
Abstract: The third-order nonlinear optical properties of sol-gel-derived V2O5, Nb2O5, and Ta2O5 thin films have been investigated by the third-harmonic-generation method, and the effect of the metal-oxygen bond length on the third-order nonlinear optical susceptibility chi((3)) has been examined. The chi((3)) values of V2O5, Nb2O5, and Ta2O5 thin films were 1.1 x 10(-11), 1.3 x 10(-12), and 6.1 x 10(-13) esu, respectively, which corresponds to an increase in the average bond length l(b) of the order of V-O (l(b) = 0.183 nm), Nb-O (l(b) = 0.200 nm), and Ta-O (l(b) = 0.204 nm). The current and previous results indicate that chi((3)), of these transition metal oxides with the empty d orbitals is dominated mainly by the metal-oxygen bond length rather than the valence of the metal cation. It is predicted on the basis of Lines' model that transition metal oxides with the shortest l(b) exhibit the highest chi((3)), whereas nontransition metal oxides with the longest l(b) exhibit the highest chi((3)).
Abstract: Rutile and anatase thin films have been prepared by the sol-gel method using Ti(OC3H7i)4. Third-order nonlinear optical properties of both TiO2 thin films have been investigated by the third-harmonic generation (THG) method and the effect of the polymorph of TiO2 on the third-order nonlinear optical susceptibility, chi(3), ha.s been examined. The measured chi(3) values of rutile and anatase thin films were 1.4 x 10(-12) and 9.7 x 10(-13) esu, respectively. The chi(3) values corrected for the porosity of the film were 4.0 x 10(-12) (rutile) and 2.4 x 10(-12) esu (anatase), which are about 100 times as high as that Of SiO2 glass used as standard sample (2.8 x 10(-14) esu). The measured and corrected chi(3) values were discussed in comparision with those calculated on the basis of several models.
Abstract: Third-order nonlinear optical susceptibility, chi(3), of the sol-gel derived alpha-Fe2O3 thin film has been evaluated by the third-harmonic generation (THG) method. Chi(3) of alpha-Al2O3 single crystal (1120BAR) with the same corundum structure as alpha-Fe2O3 has also been determined. The chi(3) of the alpha-Fe2O3 film was 5.8 x 10(-11) esu, which is comparable with those of organic materials with high nonlinearity. The large chi(3) value of the alpha-Fe2O3 film may be ascribed to the high refractive index of 3.00 and to the three-photon resonance as well. The chi(3) of alpha-Al2O3 single crystal was 2.9 x 10(-14) esu, which is three orders of magnitude lower than that of alpha-Fe2O3 film and almost the same as that of fused silica. The small chi(3) value of alpha-Al2O3 single crystal was attributed to the small refractive index and wide optical band gap.
Abstract: SiO2 glass fibers were prepared by the sol-gel process from Si(OC2H5)4 (TEOS) solutions containing colloidal SiO2 particles with a mean size of 16 nm. The tensile strength of the glass fibers was increased by incorporating such particles. A maximum strength of 1.7 GPa at a diameter of 10-mu-m was achieved for 800-degrees-C-treated glass fibers prepared from the TEOS solution in which the water-to-TEOS molar ratio was 3.0 and the content of colloidal silicas was 10 wt% of total SiO2. It was found that with the incorporation of silica particle the size of micropores in the gel increased, and a decrease of capillary forces, generated on the removal of the included liquid during heating of the gel at 100-200-degrees-C for drying, was observed.
