Fluorochalcogenide glasses

A new variety of chalcogenide vitreous materials—fluorochalcogenide glasses—have been synthesized by the introduction of sodium, thallium, lead, manganese, and bismuth fluorides into the Ga₂S-GeS₂ system. These glasses are characterized by high glass transition temperatures (560–670 K), an optical transmittance up to 75% in the visible (from 0.48 μm) and IR (to 7.5 μm) spectral ranges, chemical durability in reactive acid media, low crystallization ability, and the stability of physicochemical and optical properties. Depending on the introduced fluoride, the glasses can be dielectrics, semiconductors, or ionic semiconductors. The spectral investigation of fluorochalcogenide glasses by using the X-ray emission, Raman, NMR, and EPR spectroscopy reveals the complex features of their structure. The metal cations form bonds with sulfur in different structural positions. The glass network providing the mobility of sodium ions is formed in sodium fluoride-containing glasses. The formation of groupings of the [≡Ga ← F-Ge≡] type is the main structural feature of fluorochalcogenide glasses.     

Spectral properties of Er<Superscript>3+</Superscript> in alkali-zinc-tellurite,barium-tellurite-molybdate,and fluoride glasses

Glasses of three compositions—TeO₂ · ZnO · N₂O (TZN), where N is Li, Na, or K; TeO₂ · MoO₃ · BaO (TMB); and ZrF₄ · BaF₂ · LaF₃ · AlF₃ · NaF (ZBLAN)—activated by Er³⁺ or Yb³⁺ and Er³⁺ ions were synthesized and investigated. For the ZBLAN glass, the brightest luminescence of Er³⁺ ions in the visible range was observed under excitation by the irradiation of a diode laser with the generation wavelength 0.98 μm. The TZN glass is not inferior in the intensity of luminescence with the wavelength 1.55 μm to the TMB glass, having phonons of higher energy than those for the TZN glass (940 and 740 cm⁻¹, respectively). A glass was prepared with a high content of molybdenum oxide. The possibility to increase the up-conversion efficiency in tellurite glasses is considered.     

Fluorophosphate glasses doped with PbSe quantum dots and their nonlinear optical characteristics

A new fluorophosphate glass matrix containing PbSe quantum dots characterized by a narrow size distribution (ΔR/R ∼ 5–7%, where R is the size of a quantum dot) is prepared under heat treatment. It is demonstrated that fluorophosphate glasses can be doped by introducing (ZnSe + PbO) or PbSe into the composition of the glass. The optical absorption spectra of the quantum dots corresponding to the strong quantum confinement regime are studied over a wide range of quantum-dot sizes (4–18 nm). The nonlinear optical absorption is investigated at a wavelength of 1.54 μm. It is revealed that the introduction of (ZnSe + PbO) rather than of PbSe into the composition of the glass improves the bleaching contrast owing to a more uniform distribution of the quantum dots over the volume of the glass sample.     

Synthesis and Spectral Properties of Nd<Subscript>2</Subscript>O<Subscript>3</Subscript>-Doped Sodium Silicophosphate Glass

Combined UV-visible and FTIR spectral studies of undoped and Nd₂O₃ –doped sodium silicophosphate glasses were carried out to characterize the optical and structural properties of such glasses. The base undoped silicophosphate glass exhibits strong UV absorption which is due to the presence of unavoidable trace iron impurities (mainly Fe³⁺ ions) present contaminated within the raw materials used for the preparation of such glasses. Nd₂O₃ –doped glasses show characteristic absorption bands extending in the entire visible region which are attributed to the contribution of Nd³⁺ ions with distinct peaks which are almost constant with the increase of dopant. This comes from the combined compact glass structure containing two glass forming units and the shielding of the rare-earth ions. Infrared absorption spectra of the studied glasses reveal characteristic IR bands due to the combination of both silicate and phosphate groups. The introduction of Nd₂O₃ within the dopant level (2 %) produces no variations in the IR vibrational bands due to the presence of the two structural silicate and phosphate groups giving compactness of the network structure. The deconvoluted spectra reveal the presence of phosphate groups in a slightly high ratio due to the high content of P₂O₅ in the composition.     

Electrical conductivity and structure of glasses in the Na<Subscript>2</Subscript>O-Na<Subscript>2</Subscript>S-P<Subscript>2</Subscript>O<Subscript>5</Subscript> and Na<Subscript>2</Subscript>S-P<Subscript>2</Subscript>S<Subscript>5</Subscript> systems

The glasses, in which oxygen was partially replaced with sulfur, have been synthesized in the Na₂O-P₂O₅-Na₂S system. The chemical and chromatographic analyses of the glasses synthesized have been performed. The temperature-concentration dependences of electrical conductivity of the glasses have been studied over a wide temperature range; the glass transition temperatures and the nature of charge carriers have been determined. The IR spectra and Raman spectra have been recorded at room temperature; the density and microhardness of the glasses and ultrasound velocity have been measured. A comparison of the electrical conductivities of the investigated glasses with those of the earlier studied glasses in the Na₂O-P₂O₅ system has shown their fair coincidence. The introduction of sodium sulfide into the Na₂O-P₂O₅ system is accompanied by an approximately threefold increase in electrical conductivity, although the concentrations of charge carriers (sodium ions) in the glasses amount to ∼17 and ∼26 mmol/cm³, respectively. The rise in electrical conductivity has been assumed to be caused by the increase in the degree of dissociation of polar structural chemical units including sulfide ions and by the higher mobility of sodium ions in the oxygen-free matrix.     

Template synthesis of mesoporous silicas containing phosphonic groups

Mesoporous silicas containing the functional group ≡Si(CH₂)₂P(O)(OC₂H₅)₂ in the surface layer have been obtained using the template method (template—P123). Their treatment by a concentrated hydrochloric acid results in the formation of functional groups of the composition ≡Si(CH₂)₂P(O)(OH)₂ that is in agreement with the IR spectroscopy data. It has been shown that the above treatment causes an increase of the sample specific surface area (up to 605 m²/g), sorption capacity, and pore diameter. As established by means of the CP/MAS NMR spectroscopy on ³¹P nuclei, the sample drying in vacuum at 110°C results in the formation of fragments ≡Si(CH₂)₂P(O)(OH)—OSi≡ with the content of 10–15 wt %. However, according to the TEM data, the sample mesoporous structure is retained.     

UV-Visible and IR Spectroscopic Studies of Gamma Irradiated Transition Metal Doped Lead Silicate Glasses

Lead silicate (LS) glasses of the basic composition PbO 75%, SiO₂ 25% together with samples containing (∼0.1%) of transition 3d metal oxides (Ti→Cu) were prepared. UV/VIS optical analysis for as prepared and after successive gamma irradiated samples were used to shed more light on the structural modifications that occur due to different dopants and different irradiation doses. The UV-Vis. spectral analysis for undoped glass shows induced absorption bands at 205–400 nm which are assumed to be correlated with the base host glass and dopant transition metal ion doped glasses and dose of irradiation. The positions of the bands are observed to change slightly by gamma irradiation due to the combined effect of induced defects from the host base glass or the transition metal added. Gamma irradiation is observed to cause a decrease in the intensities of the IR absorption bands of the prepared samples accompanied by losing sharpness. These features are related to more amorphicity or disorder by irradiation or to the possible changes in bond angle or bond length in the building groups arrangement.     

Optical waveguiding in novel phosphazene polymer films

Summary Planar optical waveguides of some novel phosphazene inorganic polymers with high glass transition temperatures, T _g≥ 150°C, have been prepared by spin-coating on glass and quartz substrates. Thicknesses between 0.5 and 2 μm and index steps of about Δn∼0.2 (for quartz) and Δn∼0.1 (for glass) at λ= 0.633 μm have been achieved. From one to five modes have been observed at wavelengths ranging from the green to the near infrared. Refractive indices have been well fitted to a Sellmeier dispersion equation. Waveguide losses are estimated to be around 10 dB/cm. Received: 6 December 1999/Revised version: 20 May 2000/Accepted: 15 July 2000     

Spectroscopic Studies and Luminescence Spectra of Dy<Subscript>2</Subscript>O<Subscript>3</Subscript> Doped Lead Phosphate Glasses

Dy^3 +-doped lead phosphate glasses were prepared by a melt quenching technique and investigated through Infrared absorption spectra (IR), photoluminescence (PL), and UV-Visible optical absorption measurements (UV-Vis). The luminescence spectra show two intense bands at 483 and 575 nm, which are attributed to ⁴FH_15/2 (blue) and ⁴FH_13/2 (yellow) transitions, respectively. The optical spectra data was used to evaluate the values of indirect allowed transitions. It was found that the optical band gap increases with Dy₂O₃ content. Variation in optical gap energy with the variation in localized state tails, confirms the theories for localized states in the energy gap of amorphous semiconductors. The characteristic infrared absorption bands of these glasses due to the stretching and bending vibrations were identified and analyzed by the increasing of the Dy₂O₃ content. This fact allowed us to identify the specific structural units which appear in these glasses.     

Kinetics of structural relaxation in glasses: A hierarchical model of relaxation centers

A definition is proposed for the characteristic time of structural relaxation τ_{str. rel} in metallic glasses—the universal parameter describing the kinetics of various processes associated with the structural relaxation. The behavior of τ_{str. rel} in model situations of isothermal annealing of a glass and its heating at a constant rate is considered. In the former case, the time τ_{str. rel} is equal to the age of the sample. In the latter case, after a time, τ_{str. rel} reaches a steady-state value. This is in agreement with the τ_{str. rel} values determined from the creep rate. The kinetics of structural relaxation is analyzed with due regard for the hierarchical structure of the phase space in glasses. The kinetic equation taking into account this feature is proposed, and the results of its numerical solution are given.     

Optical properties,thermal stability,and forming region of high refractive index La2O3–TiO2–Nb2O5 glasses

The high refractive index La₂O₃–TiO₂–Nb₂O₅ glasses were prepared by containerless processing, and the glass‐forming region was determined. The refractive index showed the range from 2.20 to 2.32, and the values were much higher than those of most optical glasses. The completely miscible 30LaO_3/2–(70?x)TiO₂–xNbO_5/2 (0 ≤ x ≤70) system was fabricated to study the compositional dependence of refractive index and optical transmittance. The crucial determinants of the refractive index of oxide glasses, oxygen molar volume, and electronic polarizability of oxygen ions were calculated. The principle of additivity of glass properties was suitable for the calculation of refractive index between glass and compositional oxides. All the glasses were colorless and transparent in the visible to 6.5 μm middle infrared (MIR) region. These results are useful for designing new optical glasses with high refractive index and low wavelength dispersion in wide optical window.     

Synthesis and properties of tellurite based glasses containing Na2O,BaO, and TiO2: Raman,UV and neutron/charged particle shielding assessments

In this paper, 75TeO₂–5Na₂O–20BaO?xTiO₂ (TNB-Tix with x = 0, 05, 10, and 15) glasses were synthesized by the conventional melt-quench technique using analytic grade tellurium oxide (TeO₂), barium carbonate (BaCO₃), sodium carbonate (Na₂CO₃) and titanium oxide (TiO₂) as starting chemicals. The prepared glasses were studied for their physical features, Raman and UV spectra, and shielding performance against neutrons and charged particles. The optical property was investigated by UV–Vis spectrometry while the structural evolution of the glasses was studied through the Rahman spectra. Charged particles, slow and fast neutrons interaction parameters of the glasses were calculated theoretically and analyzed as well. The prepared glasses were yellowish without any flaws. The mass density of the glasses increased from 5.1 to 5.4 g/cm³ as TiO₂ content declined from 15 to 0 mol%. Also, an improvement in the optical bandgap from 2.89 to 3.2 eV was recorded as BaO content increased concerning TiO₂ while the refractive index declined from 2.43 to 2.35. Generally, the improvement in the TiO₂ content of the glasses produced a rise in the total and scattering cross section of thermal and slow neutrons respectively. In addition, the fast neutron cross section was enhanced from 0.1005 to 0.1015 cm^?1 for TNB-Ti00 – TNB-Ti15 glasses. The charged particle shielding parameters showed a strong dependence on the chemical structure of the glass system. The present glass system displayed good properties that could make them useful in optical and shielding applications.     

Synthesis,Optical Properties,and Photoluminescence of Organometallic Acetylide Polymers of Platinum Functionalized with Si and Ge-Bridged Bis(3,6-Diethynyl-9-butylcarbazole)

A series of light-emitting group 14 element-containing organometallic platinum polyynes of the form trans-[–Pt(PBu₃)₂C≡ CArC≡ C(ER₂)C≡ CArC≡ C–] _n (Ar = 9-butylcarbazole-3,6-diyl, ER₂ = SiMe₂, SiPh₂, GeMe₂, GePh₂) were synthesized and spectroscopically characterized. The solution properties and regiochemical structures of this new structural class of organosilicon- and organogermanium-based metallopolyynes were studied by IR and NMR (¹H, ¹³C, ²⁹Si, and ³¹P) spectroscopies. The optical absorption and photoluminescence spectra of these metallopolymers were examined and compared with their well-defined dinuclear model complexes trans-[Pt(Ph)(PEt₃)₂C≡ CArC≡ C(ER₂)C≡ CArC≡ CPt(Ph)(PEt₃)₂]. The influence of the heavy platinum atom and the group 14 silyl or germyl structural unit possessing different side group substituents on the thermal and phosphorescence properties were investigated in detail. We have also established the goal for studying the evolution of the lowest singlet and triplet excited states with the nature of ER₂ unit in these metallopolymers. The present work indicates that the phosphorescence emission efficiency harnessed through the heavy-atom effect of platinum in the main chain changes significantly with the identity of ER₂ in the general orders GeR₂ > SiR₂ (R = Me, Ph) and EMe₂ > EPh₂ (E = Si, Ge). Dedicated to Professor Ian Manners in recognition of his outstanding contribution to inorganic and organometallic polymers.     

Correlation between atomic structure, structural nanoinhomogeneity, and quadratic optical nonlinearity in glasses of the K2O-TiO2-P2O5 system

The methods of small angle synchrotron radiation scattering, vibration spectroscopy, and second harmonic generation are applied to glasses of the K₂O-TiO₂-P₂O₅ system near the stoichiometry of potassium titanyl-phosphate to demonstrate that at the initial stage of phase separation, while glass remains x-ray amorphous and clear, it can possess quadratic optical nonlinearity. The emergence of nonlinearity is facilitated by the formation of nanoheterogeneities in glass whose structure resembles the structural pattern of a nonlinear-optical crystal. Acorrelation established between the structural specifics of x-ray amorphous glass and its quadratic optical nonlinearly suggests the advisability of describing the short-range and medium-range orders of glasses at the glass-formation boundary in the context of quasicrystallite models. __________ Translated from Steklo i Keramika, No. 1, pp. 7–11, January, 2006.     

Synthesis,physical, optical,structural and radiation shielding characterization of borate glasses: A focus on the role of SrO/Al2O3 substitution

In a bid to expand the amount of information available on glass systems and their potential applications for radiation shielding design, glass samples with the compositions (30-x)SrO-xAl₂O₃–68B₂O₃–2V₂O₅(x = 5, 7.5, 10, 12.5&15 mol %) coded as SABV0 - 4 were prepared by the melt-quenching technique and analyzed for their optical, structural, physical, and radiation shielding features. The glassy (amorphous) nature of the SABV glass samples was affirmed by broad peaks of X-ray diffraction spectra. Calculated values of density and molar volume shown opposite behavior and the variation of these values were discussed as structural modifications in the glass matrix. From recorded optical absorption spectra optical band gap energy (Eg)-indirect transition, Urbach energy and optical basicity were estimated. FTIR spectra were recorded for all the samples in the range 400 cm^?1 to 4000 cm^?1. The FTIR absorbance spectra unveiled the SABV network structure mainly incorporating of BO₃ and BO₄ units. Raman spectroscopy is achieved to detect the structural changes and at higher wavenumber, B–O stretching modes in [BO₃] observed with one or two NBO's. The results of ESR spectra of glasses have indicated the highly covalent environment of vanadium ions. Analysis of the photon shielding parameters of the glasses which were obtained primarily from FLUKA Monte Carlo simulations and XCOM computations revealed photon energy and glass chemical composition dependence. The mass attenuation coefficient and effective atomic number ranged from 0.2668 to 0.3385 cm²g^-1 and 12.98–15.93 accordingly as the weight fraction of Sr increased from 16.06 to 26.72% in the glasses. Generally, photon shielding ability of the SABV glasses follows the trend: SABV0 > SABV1 > SABV2 > SABV3 > SABV4. The thermal neutron total cross section follows the same trend with values fluctuating between 71.9553 and 80.6268 cm^?1. However, SABV1 showed superior fast neutron moderating capacity among the glasses. The present SABV glasses showed outstanding photon shielding ability compared to common shields. The prepared glasses are thus suitable candidates for radiation protection applications.     

Mechanical properties and structure of a nanoporous sodium borosilicate glass

The nanohardness (H) and microhardness (H _M) of sodium borosilicate glasses with and without nanopores were studied. From nanoindentation measurements, along with the hardness H, the Young’s modulus E was derived. While both H and H _M varied between ∼10 GPa and ∼7 GPa for the bulk glass, the values for nanoporous specimens were one order of magnitude lower at about 0.5 GPa. The Young’s moduli were found to be ∼82 GPa and ∼5 GPa for bulk and porous glasses, respectively. Cracks and pileups were observed, respectively, arising from microindents and nanoindents in the bulk glass, whereas none of them could be detected in the nanoporous material. The molecular structures of both glasses studied by X-ray diffraction are similar. The text was submitted by the authors in English.     

IR spectroscopic study of water in the structure of binary alkali borate glasses

The influence of the synthesis conditions and composition of binary sodium and potassium borate glasses on the spectral absorption in the wavelength range 2.5–4 µm due to the presence of structurally bound water is investigated. It is demonstrated that water in the structure of alkali borate glasses, as in the structure of alkali silicate glasses, can exist in the form of so-called free and bound hydroxyl groups that are incorporated into the glass network in different ways. The ratio between the numbers of these forms of structural water in borate glasses is determined by the synthesis conditions and composition of the glass. The synthesis under different conditions makes it possible to prepare glasses not only with different water contents but also with different ratios between the numbers of free and bound hydroxyl groups.Original Russian Text Copyright © 2005 by Fizika i Khimiya Stekla, Golubeva, Pavinich.     

Concentration dependence of electric conductivity for fluorine-containing sodium borate glasses

The influence of sodium fluoride additives on the physicochemical properties of glasses in the Na₂O-B₂O₃ systems is investigated. The introduction of sodium fluoride into the Na₂O · 2B₂O₃ and Na₂O · 3B₂O₃ glasses leads to an increase in the electric conductivity. The temperature-concentration dependence of the electric conductivity has been investigated. It is shown that, in glasses of the NaF-Na₂O · 2B₂O₃ system, an increase in the volume concentration of sodium ions from 2.4 × 10⁻² to ∼3 × 10⁻² mol/cm³ is accompanied by an insignificant decrease in the activation energy E_σ from 1.44 to 1.38 eV and a sharp (by a factor of ∼30) increase in the electric conductivity. In glasses of the NaF-Na₂O · 3B₂O₃ system, an increase in the concentration of sodium ions from 1.8 × 10⁻² to ∼2.3 × 10⁻² mol/cm³ brings about an increase in the electric conductivity by a factor of approximately 100 and an increase in E_σ from 1.6 to 1.83 eV. A further increase in the concentration of sodium ions (up to 2.5 × 10⁻² mol/cm³) virtually does not affect the electric conductivity and E_σ. At the same concentration of sodium ions (∼2.46 × 10⁻² mol/cm³) in the 9.8NaF · 90.2[Na₂O · 2B₂O₃] and 57.1NaF · 42.9[Na₂O · 3B₂O₃] glasses, the electric conductivity and the activation energy are considerably higher in the glass with a larger fluorine content. The regularities revealed are interpreted in the framework of the microinhomogeneous glass structure.     

Structural interpretation on the concentration dependence of molar volume in ternary aluminosilicate glasses containing oxides of the first and second groups of the periodic system

The concentration dependence of the molar volume of ternary aluminosilicate glasses, in which the content of R₂O (or RO) exceeds the Al₂O₃ content, is determined by the degree of depolymerization of the glass structural lattice. The molar volume in glasses with an equimolar content of R₂O (or RO) and Al₂O₃ is additive and depends on the partial values of the molar volume of the “silica” and “aluminate” components in the structural lattice. Translated from Steklo i Keramika, No. 5, pp. 8–11, May, 2000.     

Concentration dependence of electric conductivity for fluorine-containing sodium borate glasses

The influence of sodium fluoride additives on the physicochemical properties of glasses in the Na₂O-B₂O₃ systems is investigated. The introduction of sodium fluoride into the Na₂O · 2B₂O₃ and Na₂O · 3B₂O₃ glasses leads to an increase in the electric conductivity. The temperature-concentration dependence of the electric conductivity has been investigated. It is shown that, in glasses of the NaF-Na₂O · 2B₂O₃ system, an increase in the volume concentration of sodium ions from 2.4 × 10⁻² to ∼3 × 10⁻² mol/cm³ is accompanied by an insignificant decrease in the activation energy E_σ from 1.44 to 1.38 eV and a sharp (by a factor of ∼30) increase in the electric conductivity. In glasses of the NaF-Na₂O · 3B₂O₃ system, an increase in the concentration of sodium ions from 1.8 × 10⁻² to ∼2.3 × 10⁻² mol/cm³ brings about an increase in the electric conductivity by a factor of approximately 100 and an increase in E_σ from 1.6 to 1.83 eV. A further increase in the concentration of sodium ions (up to 2.5 × 10⁻² mol/cm³) virtually does not affect the electric conductivity and E_σ. At the same concentration of sodium ions (∼2.46 × 10⁻² mol/cm³) in the 9.8NaF · 90.2[Na₂O · 2B₂O₃] and 57.1NaF · 42.9[Na₂O · 3B₂O₃] glasses, the electric conductivity and the activation energy are considerably higher in the glass with a larger fluorine content. The regularities revealed are interpreted in the framework of the microinhomogeneous glass structure.