Nonlinear Optical Properties of B2O3-Based Glasses: M2O-B2O3(M = Li, Na, K, Rb, Cs, and Ag) Binary Borate Glasses

The third-order nonlinear optical susceptibilities χ⁽³⁾ of M₂O-B₂O₃ (M = Li, Na, K, Rb, Cs, and Ag) binary borate glasses have been measured by the third harmonic generation (THG) method. It is found that the enhancement of χ⁽³⁾by the structural change of BO₃ units to BO₄ units is small, while the enhancement of χ⁽³⁾ due to the formation of non- bridging oxygen is rather significant. The effects of alkali cations on the χ⁽³⁾ of alkali borate glasses are discussed in terms of the M-O bond character, focusing on the covalency of Li₂O-B₂O₃ glasses. Comparison of the χ⁽³⁾ values for Cs₂O-B₂O₃ and Ag₂O-B₂O₃ glasses which contain cations of comparable polarizability reveals that the χ⁽³⁾ value is much greater for Ag₂O-B₂O₃ glasses than for Cs₂O-B₂O₃glasses, which is possibly due to the great contribution of Ag(4 d_z2 + 5 s + 5 p_z ) hybrid orbitals to the nonlinear optical response.     

Effects of Doping Trivalent Ions in Bismuth Borate Glasses

Bismuth borate glasses from the system: 40Bi₂O₃–59B₂O₃–1Tv₂O₃ (where Tv=Al, Y, Nd, Sm, and Eu) and three glasses of composition: 40Bi₂O₃–60B₂O₃, 37.5Bi₂O₃–62.5B₂O₃ and 38Bi₂O₃–60B₂O₃–2Al₂O₃ were prepared by melt quenching and characterized by density, UV-visible absorption spectroscopy and differential thermal analysis (DTA) studies. Bismuth borate glasses exhibit a very strong optical absorption band just below their absorption edge. Glasses were devitrified by heat treatment at temperatures above their glass transition temperatures and the crystalline phases produced in them were characterized by Fourier transform infrared (FTIR) absorption spectroscopy and X-ray diffraction (XRD). Bi₃B₅O₁₂ was found to be the most abundant phase in all devitrified samples. DTA studies on glasses and FTIR and XRD analysis on crystallized samples revealed that very small amounts of trivalent ion doping causes significant changes in the devitrification properties of bismuth borate glasses; rare-earth ions promote the formation of metastable BiBO₃–I and BiBO₃–II phases during glass crystallization.     

Photochemical Hole Burning and Local Structural Change in Sm2+-Doped Borate Glasses

Photochemical hole burning (PHB) not only can be applied for data storage systems but also serves as a powerful method for studying the local structure around optical centers. The present work investigated the effects of aluminum, magnesium, and silicon ions on hole burning and the phonon sideband for borate glasses that exhibit PHB at room temperature. Hole burning was measured for the ⁵ D ₀₋₇ F ₀ transition of Sm²⁺ and the phonon sideband spectrum for the ⁵ D ₀-⁷ F ₀ transition of Eu³⁺. The hole width was closely related to local structural change, especially as it seemed to decrease with decreases in the number of nonbridging oxygens produced around the rare-earth ions. In the case of sodium aluminoborate glasses, the hole width decreased considerably with increasing alumina content. The ratio Γ_ih/Γ_h for 85B₂O3·10Al₂O₃·5Na₂O·1Sm₂O₃ glass, then, was 80 at room temperature, the largest value ever reported.     

Effect of B2O3 Addition on the Thermal Properties and Structure of Bulk and Powdered Barium Phosphate Glasses

The glass transition temperature increases and the thermal expansion coefficient and density decrease with increasing B₂O₃ concentration in a series of (100− x )(50BaO–50P₂O₅)− x B₂O₃ where x =0–10 mol% for bulk samples. According to Raman spectroscopy, the bulk BaO–P₂O₅–B₂O₃ (BaP–B) glasses consist of metaphosphate Q ² units with ring-type metaborate, diborate, and PO₄–BO₄ groups. X-ray photoelectron spectroscopy results reveal qualitatively that P–O–B bonds are formed at the surface of BaP–B glass samples ground in laboratory air over 6 mol% B₂O₃ only. The P–O–B bonds are related to the suppression of the crystallization of powdered BaP–B glasses with >6 mol% B₂O₃ during differential thermal analysis.     

Thermal, Dielectric, and Optical Properties of Neodymium Borosilicate Glasses for Thick Films

Because of their thermal, dielectric, and optical properties, new glass compositions and thick-filmed transparent dielectrics containing neodymium oxide (Nd₂O₃) were studied as a source of purer images in plasma display panels. In the present study, PbO–B₂O₃–SiO₂ and PbO–B₂O₃–SiO₂–ZnO–Al₂O₃ were used as starting glass compositions, to which up to 25 wt% of Nd₂O₃ then was added. Increased amounts of Nd₂O₃ increased the glass transition temperature and dielectric constant of the bulk glasses and decreased the coefficient of thermal expansion. The fired thick films (around 30 μm) allowed selectively visible light to penetrate and showed deep absorption properties at 585 nm that were related to an extraneous gas from neon discharge.     

Effect of Molybdenum on the Structure and on the Crystallization of SiO2–Na2O–CaO–B2O3 Glasses

Crystallization of the poorly durable Na₂MoO₄ phase able to incorporate radioactive cesium must be avoided in SiO₂–Al₂O₃–B₂O₃–Na₂O–CaO glasses developed for the immobilization of Mo-rich nuclear wastes. Increasing amounts of B₂O₃ and MoO₃ were added to a SiO₂–Na₂O–CaO glass, and crystallization tendency was studied. Na₂MoO₄ crystallization tendency decreased with the increase of B₂O₃ concentration whereas the tendency of CaMoO₄ to crystallize increased due to preferential charge compensation of BO₄⁻ entities by Na⁺ ions. ²⁹Si MAS NMR showed that molybdenum acts as a reticulating agent in glass structure. Trivalent actinides surrogate (Nd³⁺) were shown to enter into CaMoO₄ crystals formed in glasses.     

Infrared Spectra and Atomic Arrangement in Fused Boron Oxide and Soda Borate Glasses

The infrared absorption spectra of fused B₂O₃ and of a series of soda borate glasses are presented. These spectra were obtained using vacuum-pressed briquettes of the powdered glass and powdered KBr. The spectrum of fused B₂O₃ shows quite definitely that this glass does not consist of a completely continuous triangularly coordinative network. It is shown that hydrogen bonds play an important part in the atomic arrangement of the glasses of zero or low soda content. The B₂O₃ glass apparently consists of complexes of an approximate unit (B₉O₁₄)- held together by hydrogen bonds. One in nine borons is tetrahedrally coordinated. The glasses of low soda content are similar. The spectra for soda concentrations greater than 15% did not permit the determination of the atomic arrangement with exactitude, but it is shown to be quite different from that found in glasses with 10% Na₂O or less.     

Structure-Property Relations in Lanthanide Borate Glasses

Glass formation in the system Ln₂O₃-B₂O₃ (Ln = Nd, Sm) was studied. Glasses could be formed in the range from 0 to -28 mol% rare-earth oxide (Ln₂O₃), but liquid immiscibility in these systems limits the range of homogeneous glasses to 0 to 1.5 and 25 to 28 mol% Ln₂O₃. The infrared spectra indicate that the rare-earth-rich glasses are structurally similar to rare-earth metaborates (LnB₃O₆) which contain (B₃O₆)- chains. The variation in density, transformation temperature, thermal expansion coefficient, and transformation-range viscosity of these glasses with the size of the rare-earth ion is discussed. Glasses near the metaborate composition have a transformation temperature of =700°C, which is high for binary borate glasses. Glasses could not be formed in the systems EU₂O₃-, Gd₂O₃-, HO₂O₃-, and Er₂O₃-B₂O₃, even by quenching at =1300°C/s. The sudden lack of glass formation in the system Ln₂O₃-B₂O₃ with Ln³⁺ ions smaller than Sm³⁺ is explained on the basis of the size effect of the Ln³⁺ ion on the stability of (B₃O₆)- chains in these metaborates.     

Molecular Dynamic Simulation of Eu3+ -Doped Sodium Borate Glasses and Their Fluorescence Spectra

A molecular dynamic simulation was performed for sodium borate glasses containing a small amount of Eu₂O₃ to investigate the local structures of cations in glass. A new potential V_B-B in the form -A exp[-C(r - 0.239)²] was added to the regular modified Born-Mayer-Huggins-type potentials, Φ_B-B, Φ^B-O, and ΦO-O, to account for the directional tendency of the borate network structure. With this potential added, both the radial distribution of sodium borate glasses observed by small-angle X-ray diffraction and the change in coordination number of boron with sodium content obtained by NMR agreed well with the simulation. The average coordination number of Ed³⁺ ions in the simulated glasses varied from 7.5 to 8.6, depending on the composition of the host sodium borate glasses. The inhomogeneous line width of the ⁵D₀-⁷F_z emission peak also changed, depending on the sodium content, with a maximum at 18 mol% Na_zO content; this result agrees well with experimental data obtained from laser-induced fluorescence spectra.     

Optical Study of Lithium–Bismuth–Borate Glasses

Glasses with compositions x Bi₂O₃(75− x )B₂O₃25Li₂O₃ for 0≤ x ≤40 mol% have been prepared using the normal melt-quenching technique. The optical absorption and reflection spectra were recorded at room temperature in the wavelength range 190–1100 nm. From the absorption edge studies, the values of the optical band gap ( E _opt) and Urbach energy (Δ E ) have been evaluated. Optical parameters such as refractive index and complex dielectric constant have been determined. The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple–DiDomenico model. Color parameters and color difference data L ^*, U ^*, V ^*, C ^*, h _ue, W , Y _e, Δ L ^*, Δ U ^*, Δ V ^*, Δ C ^*, and Δ E have been calculated.     

Glass Scintillator for Neutron Detection

A glass scintillator which can be used as one of the main components of a slow-neutron time-of-flight spectrometer has been developed. This sodium aluminoborate glass containing 73 mole % B₂O₃ and 8.0 mole % Ce was melted under highly reducing conditions in a series of cerium-activated very high boron-containing glasses. This glass is water white with very high light transmittance for wave lengths greater than 3800 a. u. It has a neutron-detection efficiency which is 25 to 30% greater than any other known glass scintillator in the energy range 10² to 10⁴ e.v. and is considerably better than any other type of detector. It was found that the neutron pulse height increases with increasing cerium content up to a maximum and then decreases with further increases in the cerium content. The molar content of cerium required to obtain a maximum pulse height for each B₂O₃ concentration increases linearly with the increase in the B₂O₃ content. However, the maximum pulse height decreases gradually with the B₂O₃ content from 17.0 arbitrary units at 54.5 mole % to 6.7 at 73.4 mole %. This lower pulse height is still considerably above the photomultiplier noise at room temperature.     

Polyhedral Arrangements in Lanthanum Aluminoborate Glasses

We have used magic-angle spinning nuclear magnetic resonance (MAS NMR) and Raman spectroscopy to examine the polyhedral arrangements in ternary lanthanum aluminoborate glasses. We have characterized two glass-forming series: _x Al₂O₃·(1− x )LaB₃O₆ and 0.25La₂O₃· y Al₂O₃(1− y )-B₂O₃. ¹¹B MAS NMR reveals a decrease in the fraction of four-coordinated boron atoms with increases in the Al₂O₃ content in both series. ²⁷Al MAS NMR has detected four-, five- and six-coordinated aluminum atoms in complex aluminoborate networks similar to those reported elsewhere for alkaline-earth aluminoborate glasses. Raman spectroscopy reveals a variety of borate and aluminoborate moieties, including isolated groups as well as methaborate chains and rings. These results indicate that the La³⁺ ion acts as a modifier to the aluminoborate network.     

Third-Harmonic Generation from Some Chalcogenide Glasses

Third-order optical nonlinear susceptibilities (χ⁽³⁾) of some high-refractive-index chalcogenide glasses were evaluated from third-harmonic generation. Compared with oxide glasses whose χ⁽³⁾ has been known, χ⁽³⁾ of the present glasses was higher by an order of magnitude. The addition of selenium drastically increased χ⁽³⁾. The highest χ⁽³⁾ was 1.4 × 10^–11 esu, being comparable with those of high-χ⁽³⁾-organic compounds. Further, χ⁽³⁾ generally increased with increasing density in the present glasses.     

Long-Lasting Phosphorescence of Transparent Surface-Crystallized Glass-Ceramics

Transparent surface-crystallized glass-ceramics with molar compositions of 43SiO₂–2B₂O₃–30SrO–25MgO–0.05Eu₂O₃–0.8Dy₂O₃ (sample GC-A) and 43SiO₂–2B₂O₃–24SrO–6CaO–25MgO–0.05Eu₂O₃–0.8Dy₂O₃ (sample GC-B) were prepared by heat-treating the mother glasses at 850°C for 10 h. The precipitated phases in both glass-ceramics were (Sr_{1− x} Ca _x )₂MgSi₂O₇, in which Eu²⁺ and Dy³⁺ ions were incorporated. Phosphorescence with emission peaks at 470 and 480 nm that is due to the 4 f ⁶5 d –4 f ⁷ transition of Eu²⁺ ions was observed from samples GC-A and GC-B, respectively. The phosphorescence lasted for >5 h at room temperature.     

Reduction of Eu3+ to Eu2+ in Aluminoborosilicate Glasses Prepared in Air

Eu₂O₃-doped aluminoborosilicate glasses were prepared in air at high temperature. Luminescence measurements were used to investigate a valence change from Eu³⁺ to Eu²⁺ ions in the aluminoborosilicate glasses. The results showed that the doped Eu³⁺ ions were partially reduced to Eu²⁺ in the Eu₂O₃:RO–Al₂O₃–B₂O₃–SiO₂ (RO=CaO, SrO, BaO, Li₂O) glasses, but not in the Eu₂O₃:RO–Al₂O₃–B₂O₃–SiO₂ (RO=Na₂O, K₂O) glasses. The changes of Eu reduction with different RO components were discussed with the variation of optical basicity of RO and with different valency of R cations. The effects of co-doping BaO and ZnO in aluminoborosilicate glasses on Eu reduction were also investigated and discussed.     

Energetics of La2O3–HfO2–SiO2 Glasses

A series of La₂O₃–HfO₂–SiO₂ glasses, approximately along the join 0.73SiO₂–0.27( x HfO₂–(1− x )La₂O₃), 0< x <0.3), was prepared using containerless processing techniques (aerodynamic levitation combined with laser heating in oxygen). The enthalpy of formation and enthalpy of vitrification at 25°C were obtained from drop solution calorimetry of these glasses and appropriate crystalline compounds in a molten lead borate (2PbO–B₂O₃) solvent at 702°C. The enthalpy of formation from crystalline oxides was exothermic and became less exothermic with increasing HfO₂ content. Heat contents were measured by transposed temperature drop calorimetry and depended linearly on the HfO₂ content. Differential scanning calorimetry showed that both the onset glass transition and the onset crystallization temperature of these glasses increased with increasing HfO₂ content. Upon slow cooling in air, the glasses crystallized to a mixture of baddeleyite, cristobalite, lanthanum disilicate, and hafnon.     

Ultraviolet Absorption of Pentavalent Vanadium in Binary Alkali Borate Classes

The ultraviolet absorption of vanadium(V) in R₂O-B₂O₃ glasses (R represents Li, Na, or K) and in aqueous buffer solutions was investigated. In glasses of variable R₂O:B₂O₃ ratio, a change in the absorption spectra similar to the [VO₄]³- → [VO₃(OH)]^2- change in aqueous solution was observed. It is suggested that vanadium(V) in these glasses may be present as either [VO₄]^3- or [VO₃O_1/2]^2- (O_1/2 indicates a bridging oxygen ion), depending on the basicity of the melt. The critical R₂O concentration, above which this change in vanadium(V) environment occurs with increasing alkalinity, is 24, 26, and ≅30 mol%, for K₂O, Na₂O, and Li₂O, respectively.     

Thermal Expansion of Substituted Copper Aluminosilicate Glasses

The effects of various components on the thermal expansion coefficient of low-expansion Cu₂O-Al₂O₃-SiO₂ glasses were examined. When a component of glass was substituted by another oxide, the expansion coefficient always increased, except for substitution of Al₂O₃ by B₂O₃. This result indicates that the essential components to maintain the low expansivity are Cu₂O, such trivalent oxides as Al₂O₃ and B₂O₃, and tetravalent oxide SiO₂. Glasses of the systems Cu₂O-Al₂O₃-B₂O₃, Cu₂O-Al₂O₃-GeO₂, and Cu₂O-Al₂O₃-P₂O₅, which were derived by replacing SiO₂ by other network-forming oxides, showed fairly low expansion coefficients compared with other conventional borate, germanate, and phosphate glasses. It was also found that the valence state of copper ions is important for the thermal expansion characteristics of these glasses; Cu⁺ ions contribute to the low expansion coefficient.     

Impact of Small Steel Spheres on the Surfaces of "Normal" and "Anomalous" Glasses

High-speed photography (framing rate of 10⁶ s^-1) has been used to follow the formation and growth of damage in a number of oxide glasses when impacted with 1-mm-diameter steel balls at velocities of 150 m· s^-1 or higher. Silicate, germanate, and borate glasses were studied in order to clarify the importance of "anomalous" vs "normal" elastic characteristics on their impact behavior. As expected it was found that glasses in these systems which are "anomalous" showed impact behavior which had earlier been seen in silica and borosilicate glass, whiie those glasses which are "normal" showed behavior similar to that shown by soda-lime silica glass. On the other hand, although B₂O₃ has been characterized as "normal," its impact, as well as its quasi-static behavior, appears to put it in a class by itself. In this case, no cracking is observed during loading up to 150 m·s^-1, while radial and lateral cracking are seen during unloading.     

Compositional Dependence of Absorption and Fluorescence of b3+ in Oxide Glasses

The integrated absorption cross section, the spontaneous emission probability, and the stimulated emission cross section of Yb³⁺ were determined in silicate, phosphate, borate, germanate, aluminate, gallate, and ZBLAN host glasses. The compositional dependence of the stimulated emission cross section of the ²F_5/2→²F_7/2 transition is determined mainly by the integrated absorption cross section in the glasses. A peak stimulated emission cross section above 1 pm², which is the highest value in glasses, was obtained in a gallate glass with a composition of 40K₂O·20Ta₂O₅. 40Ga₂O₃. The factors affecting the integrated absorption cross section are discussed using the Judd-Ofelt parameters of Er³⁺ calculated in previous studies.