Infrared study of the effect of heat treatment and irradiation on barium borate glass containing iron

A barium borate glass system was prepared containing different amounts of iron. The prepared glasses were heat treated at 550° C for 2, 6, 12, 18 and 24 h. Also the glasses were irradiated usingψ-ray at a dose of 4.805 × 10₄rad h⁻¹ for 12, 18 and 24 h. The infrared spectra were recorded for the untreated and heat treated samples. It was found that, when the Fe₂O₃ was introduced in the glass the triangle BO₃ groups were transferred to BO₄ groups. The formation of non-bridging oxygen with high concentration was also observed as a result of introducing Fe₂O₃ in the glass. The absorption bands of the IR spectra of the irradiated samples indicated no significant variations, and only a transfer of some BO₄ groups to BO₃ groups could be observed.     

Effect of B2O3 addition on microhardness and structural features of 40Na2O-10BaO-xB2O3-(50-x)P2O5 glass system

Phosphate glasses having composition, 40Na₂O-10BaO-xB₂O₃-(50-x)P₂O₅, wherex = 0–20 mol% were prepared using conventional melt quench technique. Density of these glasses was measured using Archimedes principle. Microhardness (MH) was measured by Vicker’s indentation technique. Structural studies were carried out using IR spectroscopy and³¹P and¹¹B MAS NMR. Density was found to vary between 2.62 and 2.77 g/cc. MH was found to increase with the increase in boron content.³¹P MAS NMR spectra showed the presence of middle Q² groups and end Q¹ and Q⁰ groups with P-O-B linkages. FTIR studies showed the presence of BO₃ and BO₄ structural units along with the depolymerization of phosphate chains in conformity with³¹P MAS NMR.¹¹B NMR spectra showed increase in BO₄ structural units with increasing boron content. The increase in MH with B₂O₃ content is due to the increase of P-O-B linkages and BO₄ structural units as observed from MAS NMR studies resulting in a more rigid borophosphate glass networks.     

Relationship between the local structure and spontaneous emission probability of Er3+ in silicate,borate, and phosphate glasses

Extended X-ray absorption fine structure (EXAFS) measurements have been performed on Er³¹ in silicate, borate, and phosphate glasses in order to investigate the local structure surrounding the Er³¹.Er³¹ ions coordinate to non-bridging oxygen ion sites, where alkali or alkaline earth ions terminate the network structure of silicate glasses. In borate glasses, the local structure surrounding Er³¹ ions is altered by the structural change ofthe borate anion. Er³¹ ions coordinate to non-bridging oxygen ion sites and BO₄ structural units in the cases with and without the formation of non-bridging oxygen, respectively. The former is similar to the case in silicate glasses. Er³¹ ions selectively coordinate to the PyO site regardless of the glass composition variation. A correlation was observed between the spontaneous emission probability for ⁴I_13/2 → ⁴I_15/2 transition of Er³⁺ and the average Er–O distance calculated by EXAFS analysis. It shows the maximum value near 2.32 Å, and we conclude that the overlapping radial integral of the 4f and 5d orbitals of Er³⁺ would be the largest at the optimum Er³¹– O²² distance 2.3 Å.     

EXAFS and MAS NMR studies of sodium molybdophosphate and sodium tungstophosphate glasses

The local order around molybdenum and tungsten atoms in various sodium molybdophosphate and sodium tungstophosphate glasses has been investigated using extended X-ray absorption fine structure (EXAFS). Both molybdenum and tungsten atoms are present in six-coordinated environment in these glasses. Magic angle spinning nuclear magnetic resonance (MAS NMR) of³¹P suggests that metaphosphate or neutral [POO_3/2] groups are present in these glasses.     

The effect of substitution of Bi2O3 for alkali oxides on thermal properties, structure and wetting behavior of the borosilicate glass

The effect of substitution of Bi₂O₃ for alkali oxides in the borosilicate sealing glass on thermal properties, structure and wetting behavior of the borosilicate glass was studied. The thermal expansion coefficient (TEC) decreased with the substitution, however, the TEC varied little while the alkali oxides were completely consumed. The variation in glass transition temperature (T_g) and the FTIR results of the glasses indicated significant effect of Bi₂O₃ substitution on the glass structure, which caused a progressive conversion of BO₃ to BO₄ unit in the glass. The appropriate amount of Bi₂O₃ obviously improved the wetting performance of the borosilicate glass on Al₂O₃ substrate due to the high polarizability of Bi³⁺ ion.     

Linear and non-linear optics and FTIR characteristics of borosilicate glasses doped with gadolinium ions

Borosilicate glasses have been prepared using the high-temperature melt components of ingredients Gd₂O₃ doped borosilicate glasses. FTIR spectra were measured in the wavenumber range (4000–400 cm⁻¹) to explore the state and influence of Gd³⁺ ions in the structure of the glasses. Data indicated that B₂O₃ is acting as dual network formers (BO₃) and (BO₄) structural units whereas the gadolinium ions playing the role of network modifier in these glasses. Optical transmission spectra were recorded in the range 190–2500 nm and different optical parameters such as the direct and the indirect optical band gap, Urbach energy, refractive index and optical dielectric constant, have been determined. The molar refraction, electronic polarizability and the optical basicity results have been determined using the measured glass refractive indices. Gadolinium-doped borosilicate glasses are found to be characterized by different optical parameters.     

Towards modeling gadolinium-lead-borate glasses

Infrared spectra of gadolinium-lead-borate glasses of the xGd₂O₃·(100 − x)[3B₂O₃·PbO] system, where x = 0, 5, 10, 15, 25, 35 and 50 mol.%, have been recorded to explore the role of content of gadolinium ions behaving as glass modifier.The FTIR spectroscopy data for the xGd₂O₃·(1 − x)[3B₂O₃·PbO] glasses show the structural role of lead ions as a network-formers and of the gadolinium ions network modifiers. Adding of the rare earth ion up to 35 mol.% into the glass matrix, the IR bands characteristic to the studied glasses become sharper and more pronounced.Structural changes, as recognized by analyzing band shapes of IR spectra, revealed that Gd₂O₃ causes a change from the continuous borate network to the continuous lead-borate network interconnected through Pb-O-B and B-O-B bridges and the transformation of some tetrahedral [BO₄] units into trigonal [BO₃] units. Then, gadolinium ions have affinity towards [BO₃] structural units which contain non-bridging oxygens necessary for the charge compensation because the more electronegative [BO₃] structural units were implied in the formation of B-O-Gd bonds and the transformation of glass network into a glass ceramic.We propose a possible structural model of building blocks for the formation of continuous random 3B₂O₃·PbO network glass used by density functional theory (DFT) calculations.DFT calculations show that lead atoms occupy three different sites in the proposed model. The first is coordinated with six oxygen atoms forming distorted octahedral geometries. The second lead atom has an octahedral oxygen environment and the five longer Pb-O bonds are considered as participating in the metal coordination scheme. The third lead atom has ionic character. In agreement with the results offered by the experimental FTIR data, the theoretical IR data confirm that our proposed structure is highly possible.     

Raman spectroscopic investigation of sodium borosilicate glass structure

Raman spectra of sodium borosilicate glasses with a wide range of Na₂O/B₂O₃ ratios were systematically measured. Variations of the spectra with glass composition were studied to interpret the implied distribution of Na⁺ ions between silicate and borate units. When Na₂O/B₂O₃ is less than 1, all Na⁺ ions are associated with borate units as indicated by the absence of the 1100 cm⁻¹ band of Si-O⁻ non-bridging bond stretching. For the (1−x)Na₂O · SiO₂ ·xB₂O₃ glass withx≦0.4 the peak-height ratio of the 950 cm⁻¹ band to the 1080 cm⁻¹ band was used to analyse semiquantitatively the distribution of the Na⁺ ions between silicate and borate units. Sodium ions are divided between silicate and borate units approximately in proportion to the amount of SiO₂ and B₂O₃ present in these glasses. Some of the high sodium content glasses were crystallized and their spectra were compared with the bulk glass spectra. The distribution of Na⁺ ions in the glass was quite different from their distribution after crystallization. Spectra of high silica glasses that had been heat-treated for phase separation indicated exclusion of borate units from the silica network and the formation of borate groups. For high boron content glasses, no change was observed on heat treatment. Raman bands due to borate groups seem to be little affected by their environments. Also affiliated with the Department of Geosciences.     

Behavior of indium oxide in zinc phosphate and borophosphate glasses

The effect of indium oxide on the structure and properties of zinc phosphate and zinc borophosphate glasses has been investigated in the series (50?x)ZnO–xIn₂O₃–50P₂O₅ and 30ZnO–(20?x)B₂O₃–xIn₂O₃–50P₂O₅ with x = 0–20 mol% In₂O₃ in both series. Their physical properties were measured, and their structure was studied by Raman and NMR spectroscopy. Glass transition temperature in the phosphate glass series increases with increasing In₂O₃ content as well as their chemical durability. The observed changes in the ³¹P MAS NMR spectra with increasing In₂O₃ content revealed the depolymerization of phosphate chains due to the replacement of ZnO by In₂O₃ resulting in an increase in the O/P ratio in the glass structure. ¹¹B MAS NMR spectra revealed the presence of BO₄ units in the glass structure in the borophosphate glass series; these spectra give no evidence for the formation of B–O–In bonds. Their glass transition temperature slightly decreases with increasing In₂O₃ content. The values of the molar volume in these glasses do not change substantially when B₂O₃ is replaced by In₂O₃. This can be ascribed not only to differences in boron (BO₄) and indium (InO₆) coordination, but also to a higher ionicity of In···O bonds in comparison with B–O bonds. The obtained data resulted in the conclusion that indium oxide behaves as a modifying oxide in both glasses.     

Spectroscopic characterization of alkali borosilicate glasses containing iron ions

Structural properties of alkali borosilicate glasses containing iron ions were investigated using infrared, laser Raman and Mössbauer spectroscopy. Two types of glasses were prepared: SRL-type with the composition 18.5 wt% Na₂O, 10.0 wt% B₂O₃, 52.5 wt% SiO₂, 4.0 wt% Li₂O, 10 wt% TiO₂ and 5.0 wt% CaO, and sodium borosilicate glass with the composition 16.7 wt% Na₂O, 18.7 wt% B₂O₃ and 64.6 wt% SiO₂. Raman spectroscopy showed that orthosilicates are the dominant amorphous phase in the SRL-type of glass. Incorporation of iron in the SRL-type of glass induced polymerization of silicate units and -Si-O-Fe- copolymerization. It was concluded that different amorphous phases are simultaneously present in the SRL-type of glass containing iron ions. Interpretation of the Raman spectra is given. Incorporation of iron ions into the sodium borosilicate glass also affected the corresponding IR spectra. The valence state of iron and its coordination were determined by⁵⁷Fe Mössbauer spectroscopy.     

Optical and EPR studies on Cu2+-doped sodium borobismuthate glasses

Heavy metal oxide glasses are becoming a good infrared (IR) transmitting windows. The optical, differential scanning calorimeter (DSC), FTIR and EPR studies of Cu²⁺-doped sodium borobismuthate glasses have been investigated. The FTIR studies show that the glassy system contains BO₃ and BO₄ units in the disordered manner. The optical studies confirm the presence of Cu²⁺ ions in the glassy network. The EPR studies show that the Cu²⁺ ions are deposited in the distorted octahedral sites elongated on the z-axis.     

Two-phase porous silica: Mesopores inside controlled pore glasses

The structural and textural properties of Two-Phase Porous Silica consisting of a mesoporous pore system formed by finely dispersed silica-gel inside the original pores of a macroporous glass framework have been carefully investigated. Nitrogen adsorption at 77 K, Mercury Intrusion, Small Angle X-ray Scattering (SAXS), Temperature-Programmed Desorption (TPD) of ammonia and ²⁷Al MAS NMR spectroscopy were used. Different mesoporous glasses investigated show BET surface areas up to 300 m²/g, a total pore volume of about 0.16 cm³/g and pore sizes of <2–10 nm, depending on the acid leaching conditions of the phase-separated sodium borosilicate initial glass. The texture of the macroporous frame glass was characterized after removing the mesoporous finely dispersed silica-gel phase with alkaline solution. Leaching of the phase-separated initial glass with Al(NO₃)₃ solution and followed by thermal treatment lead to the formation of Brönsted acid sites at the surface of the resulting mesoporous glasses by an incorporation of aluminium in tetrahedral coordination in the silica framework.     

Study of lithium–zinc borophosphate glasses

Mixed lithium–zinc borophosphate glasses were prepared and studied in three compositional series xLi₂O–(50−x)ZnO–50P₂O₅, xLi₂O–(50−x)ZnO–10B₂O₃–40P₂O₅ and xLi₂O–(50−x)ZnO–20B₂O₃–30P₂O₅ with x = 0, 10, 20, 30, 40 and 50 mol% Li₂O. The obtained glasses were characterized by the measurements of the density (ρ), molar volume (V _M), glass transition temperature (T _g) and thermal expansion coefficient (α). For the investigation of structural changes ¹¹B and ³¹P MAS NMR and Raman spectroscopy were applied. The replacement of zinc by lithium in borophosphate glasses slightly decreases V _M and T _g, while α increases. In Li–Zn metaphosphate glasses the compositional dependence of T _g reveals a minimum, while at the borophosphate series T _g decreases monotonously with increasing Li₂O content. Chemical stability of Li–Zn borophosphate glasses is very good for glasses with x = 0–30 mol% Li₂O. Spectral studies showed in the glass series with 10 mol% B₂O₃ only the presence of BO₄ sites. In the glasses with 20 mol% B₂O₃ the presence of BO₃ and two BO₄ sites was revealed in ZnO-rich glasses and only one BO₄ site in Li₂O-rich glasses; the number of BO₃ groups decreases with increasing Li₂O content which is ascribed to the formation of P–O–Zn covalent bonds in ZnO-rich glasses.     

Contact angle of E and borosilicate glasses in different atmospheres

The contact angle of E and borosilicate glasses in various atmospheres such as air, steam, glycols, etc, show that the ambient atmosphere significantly affects the wetting behaviour of these glasses with platinum 20% rhodium alloy. The change in the contact angle is attributed to the bond formation between the cations and anions in the substrate, glass and atmosphere. Steam and oxygen which increase the non-bridging oxygens in the glass as well as increase the negativity of the glass surface increase wetting. Glycols and glycerins reduce non-bridging oxygens and increase the surface positivity groups which reduce wetting. As the requirement of oxygen for complete oxidation of atmospheric combustibles increases, the wetting increases and consequently the contact angle decreases.     

Viscosity properties of sodium borophosphate glasses

The viscosity behavior of (1 − x)NaPO₃−xNa₂B₄O₇ glasses (x = 0.05-0.20) have been measured as a function of temperature using beam-bending and parallel-plate viscometry. The viscosity was found to shift to higher temperatures with increasing sodium borate content. The kinetic fragility parameter, m, estimated from the viscosity curve, decreases from 52 to 33 when x increases from 0.05 to 0.20 indicating that the glass network transforms from fragile to strong with the addition of Na₂B₄O₇. The decrease in fragility with increasing x is due to the progressive depolymerization of the phosphate network by the preferred four-coordinated boron atoms present in the low alkali borate glasses. As confirmed by Raman spectroscopy increasing alkali borate leads to enhanced B-O-P linkages realized with the accompanying transition from solely four-coordinated boron (in BO₄ units) to mixed BO₄/BO₃ structures. The glass viscosity characteristics of the investigated glasses were compared to those of P-SF67 and N-FK5 commercial glasses from SCHOTT. We showed that the dependence of the viscosity of P-SF67 was similar to the investigated glasses due to similar phosphate network organization confirmed by Raman spectroscopy, whereas N-FK5 exhibited a very different viscosity curve and fragility parameter due to its highly coordinated silicate network.     

Mechanochemical synthesis of SnO-B2O3 glassy anode materials for rechargeable lithium batteries

The xSnO·(100 ? x)B₂O₃ (0 ≦ x ≦ 80) glasses were successfully prepared by a mechanical milling technique. The glass with 40 mol% SnO showed the maximum glass transition temperature of 347°C. The SnO-B₂O₃ milled glasses consisted of both BO₃ and BO₄ units, and the fraction of BO₄ units was maximized at the composition of 50 mol% SnO. The electrochemical properties of the milled glasses were examined using a simple three electrodes cell with a conventional liquid electrolyte. The glasses with high SnO content exhibited high charge capacities more than 1100 mAh g^?1 and discharge capacities more than 700 mAh g^?1 at the first cycle. The SnO-B₂O₃ milled glasses proved to work as anode materials for rechargeable lithium batteries.     

Raman spectroscopic investigation of the structure and crystallization of binary alkali germanate glasses

Raman spectra have been measured on bulk GeO₂ glass and the alkali germanate glasses of composition M₂OxGeO₂ where M=K, Na, Li, and x varies from 19 to 1, as well as on crystallized glasses. The low alkali content glasses (x3) retain a completely polymerized structure of germania polyhedra. Addition of small amounts of alkali oxide to GeO₂ glass does not break the Ge-O-Ge bridging bonds and creates higher co-ordination of germanium atoms. Further addition of alkali oxide eventually breaks up some of the Ge-O-Ge bonds to create Ge-O^– non-bridging oxygens. In the K- and Na-glasses a small number of non-bridging oxygens already exist at x=4.5, while in the Li-glasses they do not exist even at x=4. The structures of the low alkali content glasses start to disappear at x between 4 and 3 and they disappear almost completely at x=2. At x between 2 and 1, glass structures become analogous to the silicate glass structures. At x=2, the glass consists of disordered (Ge₂O₅) _n sheet-like structures and at x=1 disordered (GeO₃) _n chain structures.     

ESCA study on the mechanism of adherence of metal to silica glass

Indium oxide films formed on the surface of silica glass samples by selective oxidation have been shown to greatly improve the adherence of gold-indium alloy to the silica glass. In order to clarify the role that the oxide films play in the reaction, thin indium films have been evaporated onto silica glass and heated at temperatures of between 973 and 1473 K, both in air and in hydrogen gas. Electron spectroscopy for chemical analysis (ESCA) measurements have then been made to investigate the chemical environments around oxygen and indium atoms at the reacting interface between the oxide and glass. Measured 01s and In3d _5/2 spectra reveal the formation of non-bridging oxygen atoms at the interface, in addition to the original bridging oxygen atoms in silica glass. Introduction of the non-bridging oxygen atoms and indium ions into the silica glass is concluded to be an essential factor in promoting good adherence between the gold alloy and silica glass.     

The effect of chloride ions on the optical properties of TeO2-CuO-CuCl2 glasses

The glasses with composition 65TeO₂-(35–x)CuO-xCuCl₂ (x=0, 1, 2, 3, 4, 5 mol%) were prepared by a melt quenching technique and thin films of different thicknesses were made by blowing. The optical energy gap was studied and its variation with composition is discussed in terms of the effective role played by chloride ions which reduce the non-bridging oxygen ions and modify the structure of the network. The infrared spectra of all these glass samples at room temperature, recorded between 200 and 2400 cm^–1, are discussed in terms of anti-symmetric vibrations of the heteronuclear atoms.     

Effect of barium on diffusion of sodium in borosilicate glass

Diffusion coefficients of sodium in barium borosilicate glasses having varying concentration of barium were determined by heterogeneous isotopic exchange method using (24)Na as the radiotracer for sodium. The measurements were carried out at various temperatures (748-798 K) to obtain the activation energy (E(a)) of diffusion. The E(a) values were found to increase with increasing barium content of the glass, indicating that introduction of barium in the borosilicate glass hinders the diffusion of alkali metal ions from the glass matrix. The results have been explained in terms of the electrostatic and structural factors, with the increasing barium concentration resulting in population of low energy sites by Na(+) ions and, plausibly, formation of more tight glass network. The leach rate measurements on the glass samples show similar trend.