Roger F. Bartholomew

Structure and properties of silver phosphate glasses — Infrared and visible spectra

Abstract The infrared and visible spectra of glasses in the Ag2OP2O5 glass-forming system were obtained. The infrared data were interpreted as indicating the presence of polymeric chains in these glasses. The partial covalent nature of the AgOP bond was discussed. A mixed NaPO3AgPO3 glass showed no unexpected bands in the infrared spectrum, again showing that silver is behaving in a manner similar to alkali metal ions in phosphate glasses. The shift in the absorption edge in the visible spectra of glasses of different Ag/P ratio was shown to arise from either an increase in the concentration of nonbridging oxygens with increasing silver content, or the presence of colloidal silver metal particles.

Wide-line NMR study of protons in hydrosilicate glasses of different water content

Abstract A wide-line NMR study is reported of glasses containing from 3.6 to 41 wt % H 2 O. Proton wide-line NMR spectra at low temperatures show that the protons are present as hydroxyl groups and water. As the temperature is increased, the line width decreases, evidence for the increased mobility of the water molecules. The hydroxyl content appears to be relatively low, almost independent of the total proton content. Na 23 spectra in a glass containing 32.5 wt % water were studied. At 100°C the Na + ions were found to be very mobile. It is shown that when the glass network is ruptured a limited number of hydroxyl groups is formed. However, most of the water is present in the opened-up glass structure as molecular water.

High-water containing glasses

Abstract The synthesis of glasses with water contents greater than a few tenths of a weight percent water necessitates the temperatures and pressures attainable in an autoclave. Compositions that readily hydrate contain both alkali metal oxide and silica. Examples will be presented of different composition fields. Parameters affecting the kinetics and techniques to control final water contents will be described. Structural information obtained from infrared spectra show that both hydroxyl and molecular water groups are present. Properties of the glass can be drastically altered. Physical, mechanical and chemical properties will be discussed.

Electrical properties of phosphate glasses

Abstract The electrical properties of glasses in the Na2OP2O5, Ag2OP2O5 and (1−x)Na2OxAg2OP2O5 systems have been measured over a range of temperature and composition. The properties of the Na2OP2O5 and Ag2OP2O5 glasses have been compared within the phosphate system as well as with silicate glasses. The silver-containing glasses show higher conductivity and lower temperature coefficients when compared with the sodium-containing glasses. A maximum in the room temperature resistivity of the (1−x)Na2O−xAg2O−P2O5 system was found around the mole ratio of 0.16:0.84 Ag2O:Na2O, indicating a mixed-alkali effect. A similar effect was seen in the tan δ, but not in the Tg-against-composition plots. A linear relationship was noted for the tan δ-versus-log10 (resistivity) plot, as has been seen in other glass-forming systems.

Water/glass reactions at elevated temperatures and pressures

Abstract Hydration behavior of two closely related glasses was studied as a function of temperature and percent saturation of steam in an autoclave atmosphere. Temperatures ranged from 225 to 350°C under steam pressures which varied from 56 to 100 percent of saturation. These glasses hydrated to give a sharp boundary layer, with H 2 O contents (wt %) up to 17.5%. The position of this boundary (penetration), weight gain per unit area, and water content of the hydrated layer, were determined as a function of time, temperature and saturation. Penetration rates in both compositions decreased with decreasing saturation and were relatively insensitive to temperature. Water contents (by LOI) increased within the hydrated layer with decreasing temperature. The implications of these findings with regard to process control are discussed.

Pr-doped mixed-halide glasses for 1300 nm amplification

The pump efficiency of Pr-doped fluorozirconate amplifiers at 1300 nm is limited by nonradiative decay. A Pr/sup 3+1/G/sub 4/ excited state lifetime of 322 /spl mu/s has been obtained in a mixed-halide glass. This is 2.9 times longer than the lifetime in a fluorozirconate host. Numerical amplifier modeling combined with calculated emission cross sections predicts a comparable increase in amplifier pump efficiency. The mixed-halide /sup 1/G/sub 4/ emission is peaked at 1310 nm.<<ETX>>

Praseodymium-doped cadmium mixed halide glasses for 1.3 μm amplification

Abstract In the search for suitable glass hosts for 1300 nm amplification, the field has been narrowed to Pr-doped fluorozirconate, fluoroindate, cadmium mixed halide and sulphide glasses. This paper presents data identifying the cadmium mixed halide system as a leading candidate, based on the lifetime and quantum efficiency of the1G4 →3H5 fluorescence of Pr3+ in this system. Compositional studies to develop cladding and core glasses suitable for high numerical aperture fiber, as well as relevant physical and optical properties, are also discussed.

Electrical properties of new glasses based on the Li2S–SiS2 system

Abstract Improvement of large energy density systems such as lithium ion batteries requires an understanding of the electrode materials and identification of new electrolytes. For safety reasons, solid sate electrolytes are preferred. This study is based on past results on the Li2S–SiS2 system. AC impedance spectroscopy was used to determine the ionic conductivity of glasses where additions were made of sulfides and oxides of groups IVA, VA, VB or VIA to the base glass composition 60/40 Li2S–SiS2 (mol%). These additions improved the stability of these glasses, so much so that thick samples (>2 mm ) could be prepared by cooling without quenching. Addition of lithium halides further increased conductivity. Ionic conductivities >2×10 −3 S / cm at room temperature were measured, amongst the largest reported in the glass literature for lithium electrolytes. The conductivity activation energy of these glasses will be reported.

The reaction of SO2 with molten nitrates and nitrites

Abstract Sulfur dioxide was observed to react rapidly with molten alkali metal nitrates and nitrites. The overall reaction of SO 2 with nitrate produced sulfate and NO 2 . Reaction of SO 2 with nitrite resulted in sulfate, NO, NO 2 , and N 2 O as major products. Reaction schemes are suggested to account for the observed products.

Structure of CLAP glasses

Abstract In AlF3-based glasses (CLAP), variations of oxygen as small as 0.2 wt% are observed to have order of magnitude effects upon glass stability, to the extent that monophase glasses can be formed only at normal quenching rates when the oxygen concentration is 1.1 ± 0.3 wt%. Glass compositions within this concentration band were prepared and studied by extended X-ray absorption fine structure and Raman spectroscopy. These data and oxygen dependence of other properties, some of which have already been reported, are used to propose a structural model based upon the coexistence of chemically perturbed regions, of the order of 1 nm in size.