Search

In addition to the total attenuation of ionizing radiation, photoluminescence has been conventionally recognized to affect radiation-induced luminescence. In this study, we examined the optical and luminescence properties of Ce3+ in lithium silicate-based glasses with different optical basicities. The existence of Ce4+ was confirmed based on the optical absorption, Ce L3-edge X-ray absorption near edge structure (XANES), and optical coefficients of the calculated Ce4+ using the optical absorption and XANES data of Ce4+ species from a previous report. Compared to other multicomponent glasses, there was a slight deviation in the decay constant and quantum yield (QY) of the stoichiometric Li2O–2SiO2 glass. In addition, the light yields calculated from the pulse height spectra with 252Cf irradiation depend on the QY of the glasses. Considering the energy conversion process, the dependence of the light yield agreed with that of the conventional energy conversion process of neutron-induced luminescence.

We have examined the X-ray-induced luminescence of Sn-doped zinc borate (SZB) glasses prepared by a conventional melt-quenching method in an Ar atmosphere, determining that there is a linear relationship between the thermal properties and SnO, in addition to the elastic properties. The scintillation intensity of SZB glasses increases with tin concentration. Meanwhile, the intensity of thermally stimulated luminescence (TSL) achieves a maximum peak area in the sample with 0.1 mol% Sn concentration. A clear inverse relationship between scintillation and TSL in SZB glasses is observed.

A face centered cubic (FCC) type Mg–Sc hydride (Mg0.8Sc0.2Hx phase) was prepared by an ultra-high pressure (UHP) technique generating an 8 GPa hydrogen pressure. Reversible hydrogen releasing and restoring behaviors have been observed by a differential scanning calorimeter (DSC) measurement at a 0.5 MPa hydrogen pressure. The hydrogen releasing temperature was lower by around 70 K than that of MgH2. The structural analysis using a Rietveld refinement of the synchrotron X-ray diffraction patterns indicated that the FCC phase was preserved without decomposition after the reproducible hydrogen releasing and restoring reactions.

The effects of the substitution of fluoride ions for oxide ions on the thermal and optical properties of ternary ZnO-Bi 2 O 3 -P 2 O 5 glass with low-P 2 O 5 content (20–25 mol%) were investigated. Fluoride ions were introduced into the glass up to about 12 mol% as ZnF 2 . Raman spectra indicated that fluoride ions were substituted for oxide ions connected with bismuth ions. Deformation and glass transition temperatures decreased monotonically with fluorine concentration. The absorption edge shifted toward higher energies with increasing fluorine concentration by about 0.3 eV for 12 mol% ZnF 2 substitution. The blue shift of the absorption edge is attributable to two effects. One was a blue shift of an absorption band which was observed as a peak at 4.7 eV in the reflection spectra and was attributed to the spin forbidden 6s–6p interband transition in Bi 3+ ions. The blue shift originates from a change in electron-donating ability through anions as expected from electronegativity or optical basicity. Another is a disappearance of a shoulder at around 4.3 eV in the reflection spectra. The latter was the major reason for the large blue shift of the absorption edge energy, because the band relating to the 4.3 eV shoulder is close to the absorption edge.

Novel quaternary hydrides Mg 7− x A x TiH 16− x (A = Li, Na, K) have been synthesized by use of an ultrahigh-pressure (UHP) technique. The Rietveld refinements for synchrotron X-ray diffraction (XRD) patterns suggest that added LiH and NaH greatly enhanced the yield of the Mg 7 TiH 16 phase. The unit cell volumes of the Mg 7− x A x TiH 16− x phases were increased with increasing the amount and the ionic radii of the alkali metals. The reversibility of the hydrogen releasing and restoring reactions was much improved by the addition of alkali metal hydrides. The reversible hydrogen storage capacities were around 3–4 wt.% for the Mg 7− x A x TiH 16− x phases on the pressure–composition isotherm (PCI) measurements. Obtained enthalpy values tend to be reduced with reducing the Δ H of the alkali metals.

We have studied the temperature coefficient of the refractive index of synthetic silica glasses with various hydroxyl impurities. The refractive index was measured at 15 °C and 35 °C at 1.707–0.238 μm wavelengths. The temperature coefficient of a low-OH group (110 wt. ppm) containing glass increased from 8.0 ± 0.2 × 10−6/°C (at 1.707 μm) to 14.0 ± 0.2 × 10−6/°C (at 0.238 μm), although it increased respectively from 7.0 ± 0.2/°C to 12.0 ± 0.2 × 10−6/°C for a high-OH group (1300 wt. ppm) containing glass. The three-term Sellmeier equation, having two terms with resonance photon energies in the vacuum ultraviolet region and one term in the infrared region, was used to analyze the wavelength dispersion of the refractive index. Increasing temperatures shifted the resonance energy in the second term by −4.14 ± 0.4 × 10−4 eV/°C for low-OH (110 wt. ppm) glass and −2.64 ± 0.4 × 10−4 eV/°C for high-OH (1300 wt. ppm) glass. The fundamental absorption edge in the vacuum ultraviolet region shifted by −8.8 ± 0.7 × 10−4 eV/°C for the low-OH glass and −6.3 ± 0.7 × 10−4 eV/°C for the high-OH glass in a region of 25–100 °C. Both high-OH glass shift rates were lower than low-OH glass shift rates. The lower temperature coefficient for the Si–OH-related band probably explains the smaller temperature coefficient for high-OH glass: the absorption band of Si–O–H structure is located at lower energy side close to the fundamental absorption band associated with the Si–O–Si structure.

Magnesium-based hydrides with Zr or Hf have been synthesized by means of an ultra-high pressure technique. Powder mixtures of MgH2 and ZrH2 or HfH2 have been heated up to 873 K under 4–8 GPa in a multi-anvil cell. New ternary phases (Mg–Zr–H and Mg–Hf–H) with a face centered cubic (FCC) structure have been formed. In the Mg–Zr hydride, the FCC phase with disordered metal–atom occupancy was observed, while a Ca7Ge-type super-lattice structure was observed in the Mg–Hf hydride. By the temperature programmed desorption (TPD) measurements, these new hydrides exhibit the hydrogen-desorption at around 543–583 K, which were 130–70 K lower than that of MgH2 at a heating rate of 10 K/min under vacuum. Desorbed hydrogen contents were estimated to be 4.2 and 3.0 mass% for Mg–Zr and Mg–Hf hydrides, respectively.

Reduction in the temperature coefficient of the optical path length, d S /d T of Li 2 O–Al 2 O 3 –SiO 2 glass–ceramics with near-zero thermal expansion coefficient was attempted using control of the temperature coefficient of electronic polarizability, ϕ , and the thermal expansion coefficient, α . The d S /d T value of 2.6 mol% B 2 O 3 -doped glass–ceramic was 12.5 × 10 −6 /°C, which was 0.9 × 10 −6 /°C smaller than that of B 2 O 3 -free glass–ceramic. On the other hand, reduction in d S /d T through B 2 O 3 doping was not confirmed in precursor glasses. Results showed that reduction in d S /d T of the glass–ceramic through B 2 O 3 doping is caused by the reduction in ϕ . The reduction in ϕ from B 2 O 3 doping was probably attributable to numerical reduction in non-bridging oxide ions with larger ϕ value by the concentration of boron ions in the residual glass phase. In addition, application of hydrostatic pressure during crystallization was effective to inhibit precipitation of β -spodumene solid solution, which thereby decreases d S /d T . The d S /d T value of B 2 O 3 -doped glass–ceramic crystallized under 196 MPa was 11.7 × 10 −6 /°C. That value was slightly larger than that of silica glass. The α value of this glass–ceramic was smaller than that of silica glass.

Preparation conditions of a FCC phase Mg 7 NbH x have been investigated in detailed by means of an ultra-high pressure technique. The FCC phase Mg 7 NbH x was obtained at 4 GPa or higher, but always coexisted with a monoclinic phase MgNb 2 H y . Although the monoclinic phase MgNb 2 H y releases only a small amount of hydrogen at around 623 K, the FCC phase Mg 7 NbH x exhibits large amount of hydrogen desorption (ca. 4.5 mass%) around 573 K of which temperature is by 140 K lower than that of MgH 2 . It was found that the hydrogen desorption temperature of the FCC hydrides tend to decrease in the following series: Mg 7 TiH x > Mg 7 NbH x > Mg 6 VH x with increasing the vacancy ratio of the 4b site.

The optical property of Li2O-Al2O3-SiO2 glass-ceramic, with a near-zero thermal expansion coefficient, crystallized under high pressure has been studied. A hydrostatic pressure of 196 MPa was applied by a hot isostatic pressing (HIP) technique during the nucleation process and the crystal growth process. The temperature coefficient of the optical path length, 1/l•dS/dT, decreased by 0.6×10-6 K-1, because the temperature coefficient of the refractive index, dn/dT, was decreased by the HIP treatment. The decrease in dn/dT was ascribed to the suppression of the temperature coefficient of the molar polarizability, φ, of the glass-ceramic crystallized by the HIP treatment. It was concluded that the suppression of φ occurs in the crystalline phase during the HIP treatment, based on the fact that the reduced 1/l•dS/dT was maintained even after the relaxation of the densified structure in the glass phase upon thermal annealing. The decrease in the number of lattice defects in the crystalline phase was hypothesized to be a cause of the reduced φ.

The gigapascal pressure thermal technique was described in detail as a new tool to produce new ternary metal hydrides. Thus, the occurrence of new phases in the A–Pd–H (A=Li, Na or Mg) system was investigated. The samples were subjected to pressures up to 6 GPa and subsequently heated up to 600 °C using LiAlH4 as an internal hydrogen source. The reaction times were remarkably short as compared to conventional methods. The new phases were revealed by X-ray powder diffraction measurements showing that this technique is promising for producing new ternary metal hydrides.

We synthesized two kinds of poly(9,9-diochtylfluorene) (PDOF) with different molecular weight distribution. One is PDOF with low weight molecular component (PDOF-l) and the other is PDOF with high molecular component (PDOF-h). The latter showed twice higher PL efficiency than the former. We investigated PL spectra and EL properties of the blended specimens of two PDOFs. The increase in PDOF-l content reduced PL intensity, conduction current at a constant voltage, and EL efficiency. We suggested the model due to excimer formation caused by the degree of freedom in motion of edge groups.

The chemical state of implanted Mg atoms has been studied in 2.48 ×1017 Mg+ ions cm-2-implanted silica glass by X-ray photoelectron spectroscopy. It was found that Mg atoms were coordinated with oxygen atoms, irrespective of the heat treatment at 900°C in an argon gas atmosphere. Mg ion implantation caused oxygen deficient species (SiOx) and increased the refractive index by about 5%. The oxygen deficient species and the refractive index change were stable against the heat treatment.

In situ investigations into the P/T field of C60 fullerene were performed using energy-dispersive x-ray diffraction techniques. Isobars were obtained at 11 and 9 GPa accompanied by isotherms at 750 and 800 K with pressure reaching 13 GPa. The P/T history and pressure isotropy were investigated with the aim of optimizing conditions for 3D polymer formation. Confirmation of the formation of 3D polymers was performed in situ; however, the reclaimed sample did not exhibit the expected high hardness value, due to depolymerization on pressure release. Isotropy in the pressure field promoted formation and retention of the face-centred-cubic structure.

The effect on transmittance and reflectance in the vacuum ultraviolet (VUV) region by doping alkali fluorides (LiF, NaF and KF) has been investigated in a ternary fluoroaluminate (18BaF 2 –37CaF 2 –45AlF 3 ) glass. The absorption edge of the glass obeys the Urbach rule and was shifted monotonically towards higher energies by increasing the concentration of each alkali fluoride. The VUV reflection peak at 11.3 eV was not sensitive to the change of the concentration of dopants. The magnitude of the edge shift was 10–20 times larger than that expected from the additive law on the magnitude of absorption coefficients of the glass and alkali fluorides. An excitonic interaction similar to that observed in mixed crystals of alkali halides is suggested from the monotonic shift toward the absorption edges of the dopants. The weak sensitivity of the reflection peak upon doping supports that the excitonic state lies predominantly around the edge energies.

Neutron diffraction measurements have been performed on normal and pressure-compacted vitreous GeO2 using the LAD spectrometer at the ISIS spallation pulsed neutron source and the SLAD diffractometer at NFL Studsvik. Four cylindrical GeO2 samples, which had been subjected to pressures between 0 (ambient pressure) and 6 GPa, were studied. The first peak of the diffraction pattern shifts to higher scattering vector magnitude, Q, with increasing density (preparation pressure), indicating a modification of the medium range order resulting from a compaction of the network cages. The real space correlation function, T(r), shows that the mean Ge–O bond length only changes very slightly for glasses prepared at pressures up to 6 GPa, inferring that GeO6 octahedra are not present in significant numbers in the glass following pressure release. However changes in the first Ge–Ge peak with increasing density indicate a progressive reduction of the mean Ge–O–Ge bond angle.

A 55ZrF 4 ·17BaF 2 ·23NaF·5EuF 3 glass was densified under 1.5, 3.0, 4.5, 6.0, and 9.0 GPa at 250°C by using a 6–8 multi-anvil-type high-pressure apparatus. The densities of permanently densified glasses increased until exhibiting a maximum value around 3.0 GPa and then gradually decreased with further increasing pressure. Local structures around Zr 4+ , Eu 3+ , and Ba 2+ in the undensified and densified glasses were investigated by means of Raman spectroscopy, Eu 3+ fluorescence spectroscopy, and Zr–K, Eu–L III , and Ba–L III EXAFS spectroscopy. The EXAFS analyses revealed that the local structure around Ba 2+ changed remarkably with applied pressure, giving a pressure dependence similar to that of density, while the local structures around Zr 4+ and Eu 3+ hardly changed. Therefore, it is concluded that the structural change around Ba 2+ , which is explained by a structural relaxation in the F − coordination environments around Ba 2+ under releasing applied pressure, is an origin of a peculiar high-pressure behavior observed in the present glass.

Melting of glass levitated in high magnetic fields has been performed by using a hybrid magnet and a CO 2 laser. A sphere of an optical glass (BK7) has been obtained through melting and cooling without any crucible. Raman scattering and electron spin resonance (ESR) of the glass sphere showed no spatial anisotropy with respect to the applied field. Microspheres of binary sodium tellurite glass were also obtained for the first time by an evaporation–condensation process in high magnetic fields. Thermal convection was suppressed under a magnetic force of −0.8 g . The size of microspheres produced under the magnetic force was about 500 nm at most. This size is one-half the size of spheres produced without a magnetic field. Raman scattering measurements on microspheres produced under the magnetic field showed different spectra from those without a magnetic field. The difference is due to a deficiency of sodium ions in the spheres produced without a magnetic field.

The structures of GeS 2 glasses permanently densified under 1.5, 3.0, 4.5, 6.0 and 9.0 GPa have been investigated by means of Ge–K EXAFS, Ge–K and S–K XANES, X-ray radial distribution, Raman scattering and optical absorption. The experimental results have been analyzed based on the structures of α (high-temperature form)-, β (low-temperature form)- and II (high-pressure form)-GeS 2 crystals. The densities of permanently densified glasses increased monotonously with increasing applied-pressure until 6.0 GPa and then reached a constant value in a pressure range from 6.0 to 9.0 GPa. With increasing densification the structure of GeS 2 glass, which is an intermediate between the structures of α-GeS 2 and β-GeS 2 at atmospheric pressure, was progressively converted into a II-GeS 2 -like structure with no large hollows. The red shift of optical absorption edge in the visible region that results from densification exhibited the same pressure dependence as that observed for density.

Coordination structures of implanted Fe, Co, and Ni ions were studied in 1.78–2.00-MeV 5 × 1016 ions/cm2-implanted silica glasses by x-ray absorption and optical absorption spectroscopies. It was found from x-ray absorption spectra that the implanted Fe, Co, and Ni ions are coordinated by ca.3 oxygen atoms. The implanted ions dispersed in glass matrix and did not form crystals. The valence of the implanted ions was about 1.5. The Fe–O, Co–O, and Ni–O interatomic distances were 190, 191, and 192 pm, respectively. In addition, it was found from optical absorption spectra that one-fifth of implanted Co ions were present as Co2+ ions in tetrahedral symmetry.

We have carried out neutron diffraction and Raman scattering measurements on the lithium disilicate glass densified by the application of high pressure. The density of the glass increased monotonically with applied pressures up to 6 GPa. A shift of the first sharp diffraction peak (FSDP) toward larger Q vectors was found in the total structure factor S ( Q ) of the neutron diffraction spectra. The Si–O bond length in an SiO 4 tetrahedron elongated by about 0.001 nm after densification under 6 GPa, while the nearest O–O distance did not change. However, an increase in distribution of the O–O distance was found after the densification. A low energy shift of 1080 cm −1 band, which is assigned to Si–O stretching mode, was observed in Raman scattering spectra of the densified glasses. It is consistent with the increase of Si–O bond length. We deduced from these results that the densification is caused by an increase of packing density of SiO 4 tetrahedron, which is accompanied by a distortion of the tetrahedron.

In situ energy dispersive x-ray measurements were performed on C60 fullerene at pressures of 2.6, 5.7 and 12 GPa and temperatures between 300 and 1100 K. The polymerization process was followed in detail and the dynamics of the phase changes measured. This has enabled us to map the P-T phase diagram and look at the dynamics of the phase transformations.

High pressure effects on optical properties of Ce3+ doped ternary fluoroaluminate (18BaF2·37CaF2·45AlF3) glass have been investigated in terms of ligand field around cerium ion. Five bands due to the 4f–5d transitions were observed in ultraviolet absorption spectra for the glass. A photoluminescence band was observed at around 300 nm under excitation at each band. The photoluminescence band shifted toward smaller energies by densifying the glass using high pressures and temperatures. An energy shift of the band was also found in in situ photoluminescence measurement under high pressure using a sapphire anvil cell. However, the shift observed under high pressure was large compared with that of the densified glass. We deduced that the large peak shift under high pressure is mainly due to a local elastic contraction around cerium ion.

A 60ZrF 4 ·30BaF 2 ·10EuF 3 glass was densified under 1.5, 3.0, 4.5, 6.0, and 9.0 GPa at 250°C using a 6–8-type multi-anvil high-pressure apparatus. The densities of permanently densified glasses exhibit a maximum value at the 3.0 GPa treatment and then a marked decrease with increasing pressure. Such a peculiar permanent densification behavior, being reported for the first time to the best of our knowledge, is discussed based on the F − coordination environments around Zr 4+ , Eu 3+ , and Ba 2+ . This behavior may be attributed to a spontaneous structure-relaxation.

Two strong peaks were observed in the electron energy loss spectra of polycrystalline AMoO3 (A=Sr and Ba) perovskites with metallic conductivities. One, observed at 1.7 eV, was attributed to plasmon loss originating from conduction electrons. This explains the reddish color observed. The other, located at ∼5 eV, was attributed to the charge transfer transition from the Mo4d–O2p bonding band to an unoccupied t2g band through photoemission, ultraviolet inverse photoemission, and x-ray absorption near edge structure spectra. No intense peaks were detected in the energy region between the two absorption bands (2.5

The chemical state and coordination state of copper ions have been studied in 2 MeV, 1 × 10 17 Cu + ions/cm 2 -implanted silica glass by X-ray absorption fine structure spectroscopy. It was found that the implanted Cu atoms are mainly present as Cu(I) state in the glass from the comparison of X-ray absorption near edge structure spectrum of the glass with those of CuO, Cu 2 O, CuAlO 2 , CuFeO 2 , Ca 2 CuO 3 and MgCu 2 O 3 crystals. We inferred from the extended X-ray absorption fine structure spectra that the implanted Cu atoms are coordinated by two oxygen atoms and the Cu–O interatomic distance is 0.188 nm in the glass.

Thermal relaxation of Si–O–Si bond angle has been studied in 1 MeV B + -ion, 1 MeV O + -ion and 4 MeV Ni 2+ -ion implanted silica glasses by infrared reflection and visible and near-infrared reflection spectroscopy. It is found that the change in Si–O–Si bond angle is not proportional to the change in molar volume upon annealing. It is deduced that the relaxation mechanism of Si–O–Si bond angle accompanied by little density change has an activation energy of about 100 kJ mol −1 .

The synthesis of new ternary hydrides in the Mgx MnyHz-system (x:y = 1, 2, 3, or 4:1) was investigated by applying high pressures. Powder mixtures of magnesium hydride and manganese were pressed into a pellet and compressed at a pressure of 6 gigapascal by using a machine with 6–8 multi-anvils during heating up to 873 K. The resultant samples were studied by means of X-ray powder diffraction, thermogravimetry and differential thermal analysis. A new hydride of Mg3MnH5∼6 containing at least 2.4 mass% hydrogen was found, which can be indexed as a monoclinic structure with cell parameters of a = 0.8827(2) nm, b = 0.4657(2) nm, c = 0.4676(2) nm and β = 105.72(2)◦. The desorption temperature of hydrogen was determined as 603 K.

Long-lasting phosphorescence was observed at 510 nm in a Sn2+–Cu2+ codoped Na2O–CaO–SiO2 glass at room temperature under UV illumination of 254 nm. When the glass was compressed under 3, 6, and 9 GPa, the phosphorescence shifted to 465 nm and its decay rate became shorter. The optical absorption spectra of the samples changed after compression, showing that the cupric ions were reduced to the cuprous ions. The high-pressure treatment also resulted in a lower-energy shift in the absorption edge. It was suggested that Sn2+ ions act as hole trapping centers, while oxygen vacancies surrounding by Ca2+ ions as well as active sites in the glass matrix, i.e., as electron trapping centers.

Silica glass with OH content around 1200 ppm was densified by hot isostatic pressing (HIP) to about 1%. The wavelength dispersion of the refractive index of the densified glass was measured in the region 0.238–1.71 μm. The wavelength dispersion is well explained by the three-term harmonic oscillator model modified by the extended point dipole theory, which has two terms with resonance wavelengths in the UV region and one term in the IR region. The model suggests that the resonance wavelengths depend on the density. In the present experiment, it is deduced that the resonance wavelengths in the UV region shift to the longer-wavelength with increasing density.

Novel quaternary hydrides Mg 7− x A x TiH 16− x (A = Li, Na, K) have been synthesized by use of an ultrahigh-pressure (UHP) technique. The Rietveld refinements for synchrotron X-ray diffraction (XRD) patterns suggest that added LiH and NaH greatly enhanced the yield of the Mg 7 TiH 16 phase. The unit cell volumes of the Mg 7− x A x TiH 16− x phases were increased with increasing the amount and the ionic radii of the alkali metals. The reversibility of the hydrogen releasing and restoring reactions was much improved by the addition of alkali metal hydrides. The reversible hydrogen storage capacities were around 3–4 wt.% for the Mg 7− x A x TiH 16− x phases on the pressure–composition isotherm (PCI) measurements. Obtained enthalpy values tend to be reduced with reducing the Δ H of the alkali metals.

We used an rf magnetron reactive sputtering method to prepare SrMoO3 thin film on a silica glass substrate and evaluated its optical properties. The reflectivity of the blue-colored film showed a cutoff due to plasmon at ∼1.7 eV. From a Kramers–Kronig analysis of the reflectivity, the spectral dependence of dielectric constants and optical constants were obtained. They agreed in tendency with the constants determined by spectroscopic ellipsometry. The plasma frequency due to free carriers (4.5 eV) was obtained by application of a Drude model to reflectivity values, which showed that the effective mass of the conduction carrier was m*=2.1m0, where m0 is the free electron mass.

The face-centered cubic (fcc) type magnesium-zirconium hydride (Mg0.82Zr0.18Hx) was synthesized by means of the ultrahigh pressure (UHP) technique, which could generate 8 GPa of hydrogen pressure. The differential scanning calorimeter (DSC) measurements indicated that the fcc phase exhibited reversible hydrogen releasing and restoring properties under 0.5 MPa of hydrogen pressure. On the pressure-composition isotherms, the released and restored hydrogen capacities were estimated to be 3 approximately 3.5 wt %. The Rietveld analysis for synchrotron X-ray diffraction (XRD) data showed that the fcc phase had around 70 wt % mass fraction and was preserved without decomposition during hydrogen releasing and restoring cycles.

Transmittance and refractive index in the ultraviolet (UV) region have been measured for glasses in the systems MgF 2 CaF 2 AlF 3 and BaF 2 CaF 2 AlF 3 . Cutoff wavelengths of these glasses are about 160 nm. Refractive index at 248 nm is 1.43 for a 20MgF 2 ·50CaF 2 ·30AlF 3 glass and 1.45 for an 18BaF 2 ·37CaF 2 ·45AlF 3 glass. Wavelength dispersion (−d n /d λ ) of these glasses at 248 nm is 0.6 times that of a silica glass. Under irradiation by 248 nm light by a KrF excimer laser, the glasses show no decrease in transmission to an accumulated dose of 5 × 10 3 J/cm 2 . These optical properties assure that the glasses can be used as lens materials in the UV region.

The face-centered cubic (fcc) type magnesium-zirconium hydride (Mg0.82Zr0.18Hx) was synthesized by means of the ultrahigh pressure (UHP) technique, which could generate 8 GPa of hydrogen pressure. The differential scanning calorimeter (DSC) measurements indicated that the fcc phase exhibited reversible hydrogen releasing and restoring properties under 0.5 MPa of hydrogen pressure. On the pressure-composition isotherms, the released and restored hydrogen capacities were estimated to be 3 approximately 3.5 wt %. The Rietveld analysis for synchrotron X-ray diffraction (XRD) data showed that the fcc phase had around 70 wt % mass fraction and was preserved without decomposition during hydrogen releasing and restoring cycles.

Structure analysis has been performed on permanently densified lithium silicate glasses by means of Raman scattering and ultraviolet (uv) reflection spectra. Higher energy shifts of Raman bands at around 450 and 580 cm-1 and lower energy shift of first uv reflection band were found after densification. It is deduced that these shifts are due to the decrease of Si-O-Si bond angle and the increase of Si-O bond length. The decrease of the magnitude in densification and these band shifts with lithium concentration might be due to obstruction of the structural change by lithium ions.

We have investigated the effect of high-pressure on the crystallization of an Li 2 O-Al 2 O 3 -SiO 2 glass. The glass was heated for nucleation, followed by heating for crystal growth. Hydrostatic pressure of argon gas of 196 MPa was applied in either the nucleation process or the crystal growth process, and in both the processes. β-quartz solid solution was precipitated in all glass-ceramic specimens. The crystallinity of the glass-ceramics increased by applying high-pressure during the nucleation or the crystal growth process. Lattice constants of the precipitated crystal were decreased by applying high-pressure. Magnitudes of the increase of crystallinity and the decrease of lattice constants by applying pressure in the crystal growth process were larger than these in the nucleation process. Density of glass-ceramic specimens increased by applying pressure in any heat treatment. It was suggested that the increase in density is due to increase of crystallinity, decrease of lattice constant and possibly densification of glass part. The refractive index increased with increasing density. The temperature coefficient of the optical path length, dS/dT, decreased by applying pressure.

Silica glasses with the OH content about 1200ppm and 100ppm have been densified with a HIP apparatus at temperatures of 1000-1300°C under pressures of 100-200MPa for 2 hours. The density of both glasses increases in proportion to the pressure at a fixed temperature. Under a fixed pressure, the density increases with the increase of temperature up to about 1100°C and reaches at constant values. The temperature to attain the constant density is slightly lower in the high-OH glass than in the low-OH glass, because the OH species decrease the viscosity of glass. Refractive index increases almost linearly with the increase in density with the same slope for both glasses. The relationship is explained well by the extended point dipole theory.

Formation of Au colloid particles and their optical property have been investigated in silica glasses implanted with Au+ ions at an acceleration energy of 1.5MeV and fluence levels of 1016-1017 ions/cm2. The Au colloid particles are formed in the as-implanted glasses. It is inferred that the average radius of Au colloid particles depends on the fluence level, although the fluence level does not affect the distribution of Au atomic concentration. The heat-treatment little affects the Au atomic distribution. The Au colloid particles grow to 4.3nm in average radius during heat treatment. It is revealed that the large nonlinear optical property of the Au+ -ion-implanted silica glass is attributed to the high concentration of the Au colloid particles in the narrow region.

The effect of impurity and density on refractive index was studied for silica glasses synthesized with direct, sol-gel, and vapor phase axial deposition (VAD) processes. Linear relationships between the refractive index and density n=Cρ+D were found in a wide wavelength region from ultraviolet to infrared. The correlation coefficient C decreased from 0.081±0.007cm3∕g at 1.707μm to 0.061±0.008cm3∕g at 0.238μm. The relationship was different from those of the VAD or direct glasses formed by high-pressure densification, that is, the coefficient increased from 0.200±0.011cm3∕g at 1.707μm to 0.229±0.012cm3∕g at 0.238μm for VAD glass. Chlorine and hydroxyl impurities affected the refractive index; however, these impurities did not cause the linear relationship. After adjusting the index according to the chlorine related effect and the effect of the sample density, the difference between the sample’s refractive indices Δ(n2−1) showed a similar dispersion relation irrespective of the synthetic process. An analysi...

Sodium tellurite glass was evaporated by irradiating a CO2 laser beam under a high magnetic field with a large gradient. Glass microspheres were formed as a cloud of soot with the condensation of the vapor from the source glass. The flow of the glass soot due to thermal convection was observed when the glass source was evaporated under a zero field, but was suppressed by applying the high magnetic field with a large gradient, which reduces gravity for the glass by a magnetic force of -0.8g in the gravitational scale. The maximum size of the microspheres decreased to about half that of microspheres formed under a zero field. Sodium concentration in the microspheres was found to increase with magnetic field. A disturbance of the motion of evaporated species due to electromagnetic force was suggested as an origin of the suppression of recondensation to the surface of source glass melt under the high magnetic field, resulting in the increase in the sodium concentration of the microspheres and in the decrease in their size.

Al+ ions have been implanted in silica glass at an acceleration energy of 200 eV and doses ranging from 1×1013 to 1×1017 ions cm−2. Infrared reflection spectra and ultraviolet, visible, and near‐infrared absorption spectra have been measured. It was found that refractive index of silica glass increased by 6%–10% after implantation of 1×1017 Al+ ions cm−2. It was deduced that this refractive index change is caused by the formation of Si—Si homobonds, but not by the decrease in Si—O—‐Si bond angle which leads to compaction.