Bulk Glass Samples Research Articles

Quantifying Raman gain coefficients in tellurite glasses

This paper presents results obtained on bulk glasses that have been fabricated and characterized for their Raman gain properties. We summarize relative values of the Raman gain coefficients of different tellurite-based glasses as compared to that of fused silica, and compare data to values estimated from their Raman cross-section data. Spontaneous Raman spectra measurements demonstrate a straight forward means to estimate Raman gain coefficients utilizing spontaneous Raman scattering cross-section data as referenced to known standards. This technique shows, for an initial set of tellurite-based bulk glass samples, excellent agreement with experimentally-obtained Raman gain coefficient data. Initial experimental measurement of Raman gain coefficients for several tellurite glasses reveal that some compositions examined exhibit an absolute Raman gain coefficient up to 30 times higher than silica, with an overall spectral bandwidth more than twice that of fused silica.

Cooling process recorded in subglacially erupted rhyolite glasses: Rapid quenching, thermal buffering, and the formation of meltwater

The thermal histories of two subglacial rhyolite glasses from Torfajökull complex of south central Iceland have been determined from changes in the relaxation of enthalpy in the calorimetric glass transition interval. Heat capacity measurements of bulk glass samples from Rauðufossafjöll (sample number JS.1.1) and Bláhnúkur (sample number JS.2.1) by differential scanning calorimetry show marked differences in the temperature of the onset of glass transition (Tg) on reheating. The average Tg is 750 K for JS.1.1, whereas it is 850 K for JS.2.1. These differences in the onset of Tg are related to quench rate through considerations of the activation energy and timescales for structural relaxation modeled, using the Kohlrausch‐Williams‐Watt function. Multiple glass samples from the two Torfajökull locations recover different average values and distributions of a fictive temperature, Tf, which we interpret in terms of differences in the thermal histories of the glasses. In both glass samples the range of fictive temperatures and, by implication, apparent cooling rates, is lower than those estimated for a glass rapidly quenched by contact with cold (glacial melt) water and requires that the glass was annealed at temperatures in the glass transition interval associated with relaxation times of the order of 1000–10,000 s. The complex cooling histories of the Torfajökull samples show that the products of subglacial eruptions may be held at elevated temperatures for several hours and, as a result, may drive vigorous convection in the ice‐bound vaults above erupting rhyolite deposits.

Preparation and characterization of Er 3+-doped TeO 2-based oxyhalide glasses

Bulk oxyhalide glasses have been prepared in the TeO 2–ZnO–ZnX 2 and TeO 2–PbO–PbX 2 systems (X=Cl, Br, I) and the corresponding glass-forming regions have been determined. Their density and characteristic temperatures were also determined. The glass-forming regions increased in the direction I → Br → Cl and were largest for the zinc-tellurite compositions. For the TeO 2–ZnO–ZnCl 2 system, compositions with 20 mol% ZnO presented the highest glass-forming ability and had high thermal stability and good infrared transmittance. The progressive replacement of TeO 2 by ZnCl 2 improved the optical quality of the glasses, as well as their thermal stability, but they became more hygroscopic. Erbium chloride was added to two base glass compositions, 40TeO 2–20ZnO–40ZnCl 2 and 60TeO 2–20ZnO–20ZnCl 2 (in mol%) and bulk glass samples could be obtained with additions of up to 10 mol% ErCl 3. Photoluminescence measurements of the erbium-doped glasses, at 1.5 μm, showed highest fluorescence intensity for the 60TeO 2–20ZnO–20ZnCl 2 compositions, especially with 3 mol% ErCl 3 with a corresponding metastable level lifetime of ∼6 ms. Higher concentrations of erbium caused a decrease of both properties.

Germanium nanoclusters in germanosilicate glass heat-treated in hydrogen

The formation of Ge nanoclusters in bulk and thin-film germanosilicate glass samples prepared by vapor deposition techniques and then heat-treated in molecular hydrogen at 800°C was studied by Raman scattering and optical spectroscopy. The results demonstrate that the formation of Ge nanoclusters is accompanied by a substantial increase in the concentration of oxygen-deficient germanium centers and the formation of OH groups. A mechanism of nanocluster formation is proposed. The effects of different process parameters on nanocluster growth in the course of preform fabrication and fiber drawing are examined.

Containerless solidification of Zr41Ti14Cu12.5Ni10Be22.5 glass-forming alloy in drop tube

Droplets of Zr41Ti14Cu12.5Ni10Be22.5 glass forming alloys with different sizes are solidified in a drop tube containerless processing. Glass transition behavior, crystallization kinetics, and the phase evolution during annealing of the Zr41Ti14Cu12.5Ni10Be22.5 glassy spheres are investigated. The experimental results indicate that the apparent activation energy of the glass transition (Eg = 435.5 kJ/mol), and the activation energy of the main crystallization reaction (E p1= 249.6 kJ/mol) are obviously different from those of bulk glass samples prepared by water quenched (Eg=559.1 kJ/mol and Ep1 =192.5 kJ/mol). The difference is discussed in the view point of the atomic configuration of the liquid state of the metallic glass and nucleation mechanism.

Processing and Characterization of Bulk Chalcogenide Glasses Used for Waveguide Applications

Chalcogenide glasses (ChG) are of interest due to their optical and electronic properties for use in waveguide applications. To assess expected uniformity in films deposited from bulk glass starting materials, the extent of parent bulk glass property variation was evaluated. Resulting structural and optical properties of melt-derived ChG's were investigated using X-ray diffraction (XRD), Raman spectroscopy, differential thermal analysis and spectrophotometric analysis. The influence of melt size, purification, and other melting conditions on sample homogeneity were quantified and within-melt property variation of bulk glass samples was found to be less than 5% for all parameters examined.

Self-diffraction of light upon optical poling of glass

The self-diffraction of light appearing upon optical poling of bulk glass samples is studied. During poling, a refractive-index grating is accumulated in the medium, on which one of the beams or both beams diffract efficiently. A theoretical expression is obtained for the amplitude of diffracted radiation. The results of the experimental study of this phenomenon in oxide glasses are in agreement with the theory, which explains the formation of a spatially periodic electric field in the medium by the coherent photogalvanic effect. The self-diffraction of light can be efficiently used for studying the physical properties of purely optical poling of media.

Polyvalent states of chromium ions in silica glasses prepared by plasma-chemical deposition

The spectral–luminescent properties of chromium-doped silica glass prepared by gas-phase plasma-chemical deposition are investigated. The absorption, photoluminescence, and EPR spectra are measured for bulk glass samples in the form of a core of optical fiber preforms. The influence of gamma irradiation and additional reducing thermochemical treatment on the spectral characteristics of the synthesized glasses is analyzed.

Effects of BaO on the glass formation of the PbO-B2O3-TiO2-BaO system in relation to transition temperatures

The variation of the BaO content on the quaternary PbO-B2O3-TiO2-BaO system's glass formation tendency was investigated in relation to transition temperatures, such as melt temperature (T f), liquidus temperature (T l), crystallization temperature (T c) and glass transition temperature (T g). Compositions were melted between 800°C and 1300°C. In order to obtain bulk glass samples, glass formation was carried out using a preheated cylindrical brass mould without forcing the cooling rate to increase. Glass formation tendency increased with increasing the temperature ratios of T g/T l and T c/T l and with decreasing T g/T c. Eutectic compositions preferentially formed glasses from melts due to their low melting temperatures.

Interferometric measurement of refractive-index change in photosensitive glass

We report on a technique for determining the change in the refractive index of photosensitive glass. We have demonstrated our interferometer-based technique on fiber preform and bulk glass samples, achieving an optical-path-difference (OPD) repeatability of 0.2 nm. For the bulk glass sample we measured an OPD of 15.2 ? 3.0 nm, corresponding to an index change of 2.1 ? 0.7 x 10(-5). Our technique was found to be insensitive to the effects of photodarkening and material compaction.

Influence of Fe3+/Fe2+ Ratio on the Crystallization of Iron‐Rich Glasses Made with Industrial Wastes

The influence of the Fe3+/Fe2+ ratio on the crystallization of iron‐rich glasses was investigated in this study. The glass batches were made from two hazardous industrial wastes: mud (goethite and jarosite) originating from the zinc hydrometallurgical process and electric arc furnace dust (EAFD). Glass compositions were prepared by adding different percentages of carbon powder. The crystallization process was investigated by a combined thermogravimetry/differential thermal analysis technique, in air or nitrogen atmospheres, using powder and bulk glass samples. The crystalline phases formed, i.e., pyroxene and spinels, and their relative ratio were determined by X‐ray diffractometry. The experimental results indicated that melting temperature and crystallization behavior were influenced by the initial Fe3+/Fe2+ ratio and by the amount of carbon added to the glass batch. For goethite and jarosite glass compositions, decreasing the Fe3+/Fe2+ ratio increased the crystallization rate by favoring magnetite formation. For EAFD glass compositions, the addition of carbon to the batch inhibited chromite–magnetite spinel formation and favored the attainment of an amorphous glassy phase.

INFLUENCE OF BOUND CHARGE ON THE SECOND-ORDER OPTICAL NONLINEARITY OF GLASS

By comparing the second-order optical nonlinearity of electrically poled glass film and bulk glass samples, it was shown that both of them have similar poling and decay behavior. After analyzing the formation of bound charge and its influence on the second-order nonlinearity of glass, a qualitative model was proposed, indicating that the electric field induced by the bound charge plays an important role on the poling and decay of both film and bulk glass.

Structures and properties of a Zr-based bulk glass alloy after annealing

A bulk glass Zr 52.5 Ni 14.6 Al 10 Cu 17.9 Ti 5 alloy with 6 mm diameter is prepared by pre-melting sponge zirconium together with other pure metal elements and followed by injecting cast. In the samples, the content of oxygen is chemically analyzed in the level of 706 ppm (atomic concentration), which significantly affects the crystallization and the microstructure. When the bulk glass samples are annealed at the temperature far below the crystallization temperature( T x ), the predominant phases of Zr 2 Ni 0.67 O 0.33 and Zr 2 Ni compounds crystallize and uniformly distribute on glass matrix. These predominant phases will grow and join together to form net-shape phase when the annealed temperature is in the range of T x to above T x . The glass matrix phase separated by the net-shape phase into the size of about 25 μm at 703 K to 15 μm at 823 K almost fully transforms into Zr 2 Ni and a small amount of Zr 2 Cu and Zr 4 Al 3 . At annealing temperatures far above T x , Zr 2 Cu and Zr 4 Al 3 compounds crystallize by phase separation to form nanostructure with nano-scale phases of Zr 2 Cu and Zr 4 Al 3 compounds distributed on the matrix of Zr 2 Ni. The micro-compressive tests by Nanoindenter II reveal that the bulk glass phase has a lower elastic modulus and lower microhardness. Increasing the annealing temperature, the modulus and microhardness for the crystallized microstructure increase. With the phase separation taking place, the modulus and microhardness for the nanostructure are improved slightly. But the different deformational mechanism between micro-scale and bulk specimens is unknown.

Laser-induced fluorescent cooling of rare-earth-doped fluoride glasses

Continual cooling of a material by anti-Stokes luminescence has been experimentally observed in a solid material. Net cooling was achieved by pumping to the lower levels of the 2F 5/2 manifold of Yb 3+, followed by population redistribution across this manifold via thermalization and fluorescence to the ground state. Fluoride glass hosts in the ZBLAN and BaF 2–InF 3–GaF 3 (BIG) families have been used in these experiments. Temperature decreases of 0.33 K in a bulk glass sample and 16 K in a fiber sample were obtained in ZBLANPb:Yb 3+. Net cooling was achieved when an electrochemical purification stage was incorporated into the glass fabrication process to decrease the extrinsic absorptive component of the host glass in the 1.0 μm region. Resonant laser ablation experiments showed the positive and negative effects of electrochemical processing on fluoride glasses in reducing transition metal content which is detrimental to successful fluorescent cooling. Reduction in copper, iron, and chromium content of 18, 4.2, and 5.5 were determined for the ZBLANPb sample via RLA. However, reductions in transition metal content were only 1.9 for copper and a negligible amount for iron and chromium in the BIG glasses.

CRYSTALLIZATION OF Na<SUB>4</SUB>Nb<SUB>8</SUB>P<SUB>4</SUB>O<SUB>32</SUB> IN BOROPHOSPHATE GLASSES

Samples with chemical composition (1-x) [0.95NaPO3-0.05Na2B4O7]-x Nb2O5 have been annealed at T≥750°C. For x≥0.3, the presence of Na4Nb8P4O32 crystalline phase were detected by X ray diffraction. The size and the distribution of micro-crystallites in the bulk glass samples were determined in relation to the thermal treatment. The crystallized glasses were studied by Raman micro probe and 31P MAS NMR and discussed in comparison with the glassy samples.

Effect of copper on conductivity of amorphous AsSe yI z

The effect of copper in AsSe y I z (for y=1.4, z=0.2) on physical and electrical properties has been examined. Temperature dependence of the electrical conductivity has also been determined. Conduction type and activation energies of electrical conductivity have been determined for Cu x (AsSe 1.4I 0.2) 100− x glasses. The study has also been concerned with spectral distribution of photoconductivity of bulk glass samples and thin films of analogous composition and with the determination of photosensitivity maxima.

Absorption spectra and luminescence of oxygen-deficient centres in a titanosilicate glass synthesised in a steady laser plume. I. Absorption spectra

The absorption spectra of titanosilicate glasses with the titanium concentration ∼ 0.1 — 3% by weight were investigated in the wavelength range 225 — 460 nm. These glasses were synthesised in a steady laser plume in an atmosphere of air or nitrogen at normal pressure. Synthesis in these two atmospheres gave rise to Ti ions of different valence in the glasses. For the same Ti concentration the intensity of the characteristic absorption bands of titanium in its reduced states (Ti2+, Ti3+) with maxima at λ ∼ 278 and 306 nm were 3 — 6 times higher when the synthesis took place in nitrogen. The enhancement of the 278 nm band was approximately half that of the band at 306 nm. Clear-cut strong absorption in the UV range at 260 — 280 nm as well as strong absorption in the visible range at 400 — 500 nm, observed for the first time for titanium-doped silica glass, were the results of a record-high concentration of Ti3+ ions, compared with the concentrations found in bulk glass samples prepared by other technologies such as melting, reduction of Ti4+ ions, and plasma hydrolysis.

Volatiles in Alkalic Basalts form the North Arch Volcanic Field, Hawaii: Extensive Degassing of Deep Submarine-erupted Alkalic Series Lavas

The North Arch volcanic field is a submarine suite of alkali basaltic to nephelinitic lavas of the seafloor north of Oahu at water depths of 3900–4380 m. Glasses from these lavas were analyzed for H2O, CO2, Cl, S, Fe3+/∑Fe, and noble gases to investigate the role of volatiles in the generation, evolution, and degassing of these alkalic series lavas. In contrast to the systemic negative correlation between concentrations of SiO2 and nonvolatile incompatible elements (e.g. P2O5), the behavior of the volatile components is much more irregular. Concentrations of H2O in glasses vary by a factor of two ( 0.69–1.42 wt %) and show a poor correlation with melt composition, whereas concentrations of dissolved CO2 in glasses (260–800 p.p.m) increase with increasing alkalinity of the glasses. The H2O2 concentrations in the glasses are in equilibrium with an H2O–CO2 vapor at the depth of eruption (400 bar pressure). Samples collected directly from vent structures are highly vesicular, suggesting that these samples were gas rich upon eruption. Estimated bulk volatile contents of the two most vesicular vent samples are high (1.9±0.1 wt % H2O and 5.4±0.4 CO2) and are interpreted to have formed by closed system degassing. Estimated bulk volatile contents in four other vesicular vent samples are lower 1.3±0.2 wt % H2O and 2.0±0.4 wt % CO2), and these samples are interpreted to have lost some gas during eruption. Glass samples from inflated, flat lava flows are nonvesicular and interpreted to have lost essentially all exsolved gas during eruption and flow. Forward degassing models can predict the observed range in dissolved H2O and CO2 contents, calculated vapor compositions, and vesicularity as a function of SiO2. The models involve open to closed system degassing of an H2O–CO2 vapor phase from melts initially having H2O/P2O5=3 and CO2H2O=1–4 mass. Cl concentrations (400–1360 p.p.m) in glasses correlate with concentrations of nonvolatile, incompatible elements. Concentrations of noble gases measured on bulk glass samples are low compared with mid-oceanic ridge basalt (MORB). The low concentrations result mainly from extensive vapor exsolution from the magma. The helium isotopic ratios for gases released from vesicles are similar to MORB values [6.8–8.5 times the air ratio (RA)], whereas those released from glasses are lower than MORB values as a result of in situ decay of U and Th. The S contents (0.11–0.22 wt %) of most of the alkali olivine basaltic and basanitic glasses are sufficient to saturate the silicate melt with immiscible Fe–S–O liquid at the T and P of eruption and quenching. However, two vesicular samples appear to hae lost some dissolved S owing to eruptive degassing. Magmatic oxygen fugacitites estimated from Fe3+/∑Fe range from ΔFMQ=-0.8 to +0.7, with the nephelinitic glasses being more oxidizing than the less alkalic glasses. We infer that the mantle source region for the North Arch magmas was homogeneous with respect to Fe3+/∑Fe and that melting occurred in the absence of graphite or CH4- rich fluid. The effect of variable partial melting on magmatic oxygen fugacity may be a common feature of Hawaiian volcanism. These complex data pint to a simple result, namely that parental magma compositions can be derived by variable extents of melting of a homogeneous source followed by olivine crystallization and degassing at 400 bar. If the parental liquids are produced by 1.6–9.0% partial melting (±20% relative), then mantle volatile contents are estimated to be 525±75 p.p.m. H2O, 1300±800 p.p.m. CO2 and 30± p.p.m. Cl.

Preparation of vitreous multicomponent fluoride films

Vitreous fluorozirconate films were obtained from bulk glass samples previously prepared by fusion. Bulk glass samples were heated between two plates at a constant rate, up to about 10°C above softening point and yet below crystallization onset temperature, under an applied load. Adherence of the films so obtained depended on heating rate and load and was good in vitreous silica, alumina and a series of metallic substrates. The films were stable and scanning electronic microscopy analysis revealed no crystallization. This technique can be applied to any stable fluoride composition.

Influence of processing parameters on the scattering properties of fluorozirconate glasses prepared by the gas film levitation technique

Fluoride glasses for optical fibre applications were prepared using a containerless processing technique (the gas film levitation technique) to prevent the contamination of the glass melts by the crucible. Bulk glass samples of high optical quality were obtained by starting directly from a powder mixture of the different fluoride precursors. Differential scanning calorimetry, laser scanning tomography and light scattering measurements were used to measure the properties of the levitated glasses as compared to crucible-made glasses prepared in the same conditions. The bulk levitated glasses had an extended thermal stability range along with improved optical properties over the crucible-made glasses.