Viscosity and shrinkage of porous and quartzoid glasses of the Na<Subscript>2</Subscript>O-B<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> system

Shrinkage of porous glasses on heating from 20 to 800°C was studied and temperature dependences of the viscosity in the range of 10¹¹–10¹³ P were determined for quartzoid (sintered) glasses based on five glasses with different compositions in the Na₂O-B₂O₃-SiO₂ system. The shrinkage of porous glasses and the viscosity of quartzoid glasses were analyzed in relation to their composition and temperature of preliminary thermal treatment.     

NMR in metal cluster compounds compared to glasses

The field and temperature dependence of the³¹P nuclear spin lattice relaxation rate in the metal cluster compound Ru₅₅(P(t-Bu)₃)₁₂Cl₂₀ follows a power law: 1/T ₁ ∝T ⁿ B ^?m , withn=1.5±0.1 at 3.25 T andn=1.3±0.1 at 6.45 T;m ? 1.4. Such dependences have so far only been observed in inorganic glasses and been attributed to two level systems. The correspondence suggests that the relaxation rate is due to interaction of theP-nuclear moment with electronic spins of stochastically moving charge carriers, which are thought to be responsible for the electrical conductivity through hopping between neigboring cluster molecules.     

Structure and electric properties of Na<Subscript>2</Subscript>SO<Subscript>4</Subscript>-NaPO<Subscript>3</Subscript> glasses

The influence of the SO₄²⁻ ion on the temperature and concentration dependences of electric conductivity and the structure of sodium phosphate oxide glasses was studied. The increased electric conductivity of sulfate-phosphate glasses was explained by the formation of mixed sulfate-phosphate fragments with terminal SO₄²⁻ ions in the structure of glasses in the Na₂SO₄-NaPO₃ system. The dissociation energies of the sodium sulfate fragments are lower than those of pure oxide sodium phosphate structural units. As a result, the number of dissociated sodium ions increases, the activation energy of electric conductivity falls, and the conductivity (at 25°C) increases approximately 270-fold relative to the conductivity of NaPO₃. The arrangement of SO₄²⁻ ions in the structure was evaluated from the IR spectra of the glasses.     

Optical transition probabilities of Er3+ in fluoride glasses

Lead-based fluoride glasses of the system PbF₂GaF₃MF₂(M = Zn or Mn) doped by trivalent erbium were prepared by melting and quenching of the appropriate fluorides under inert atmosphere. Optical spectra of the glasses with and without manganese reveal identical characteristics in the near ir region of the spectrum. In the near uv and visible part, the manganese-containing samples show higher oscillator strength, probably due to interaction between Mn²⁺ and Er³⁺. Radiative and nonradiative characteristics of the glasses were computed, using the Judd-Ofelt method. Laser transitions of the glasses were predicted.     

Concentration dependent spectral changes of electrons trapped in MgCl2 and CaCl2 glasses. A pulse radiolysis study

The aqueous MgCl₂ and CaCl₂ glasses were subjected to pulse radiolysis at 87 K. The time evolution and concentration dependence of e^-_t optical absorption spectra was examined.For MgCl₂ glasses the increase of Mg²⁺ concentration from 2.6 to 5 mol dm^-3 is followed by the shift of λ_max from 665 to 615 nm. For CaCl₂ glasses the concentration change from 3.1 to 4.5 mol dm^-3 Ca²⁺ causes the shift of λ_max from 625 to 590 nm. The blue shift is also observed during partial decay of e^-_t on μs time scale.With increasing concentration of electrolyte the contribution of e^-_ir to the total e^-_t absorption decreases, whereas that of e^-_vis increases.The ratio of [e^-_ir]/[e^-_vis] measured on micro-second time scale is significantly higher for Mg²⁺ than Ca²⁺ glasses.     

Judd–Ofelt analysis and photoluminescence properties of RE3+ (RE = Er & Nd): Cadmium lithium boro tellurite glasses

Rare earth (Er³⁺ and Nd³⁺) ions doped cadmium lithium boro tellurite (CLiBT) glasses were prepared by melt quenching method. The vis–NIR absorption spectra of these glasses have been analyzed systematically. Judd–Ofelt intensity parameters Ω_λ (λ = 2, 4, 6) have been evaluated and used to compute the radiative properties of emission transitions of Er³⁺ and Nd³⁺: CLiBT glasses. From the NIR emission spectra of Er³⁺: CLiBT glasses a broad emission band centered at 1538 nm (⁴I_13/2 → ⁴I_15/2) is observed and from Nd³⁺: CLiBT glasses, three NIR emission bands at 898 nm (⁴F_3/2 → ⁴I_9/2), 1070 nm (⁴F_3/2 → ⁴I_11/2) and 1338 nm (⁴F_3/2 → ⁴I_13/2) are observed with an excitation wavelength λ_exci = 514.5 nm (Ar⁺ Laser). The FWHM and stimulated emission cross-section values are calculated for Er³⁺ and Nd³⁺: CLiBT glasses. FWHM × σ_e^P values are also calculated for Er³⁺: CLiBT glasses.     

Ordre antiferromagne´tique dans les verres fluore´s “PbMnFeF7” et “Pb2MnFeF9”

Neutron diffraction experiments have been carried out on fluoride glasses “PbMnFeF₇” and “Pb₂MnFeF₉” to provide informations on the magnetic short range order ofM-M pairs (M =Mn²⁺, Fe³⁺). The magnetic correlation function in both glasses shows prevailing strong antiferromagnetic first neighbor interaction at 3.6Å, and two ferromagnetic interactions at 5.4 and 6.7Å. The structure of these glasses is described in terms of randomly linked corner-sharedMF₆octahedral chains, with Pb²⁺ in interstitial sites.     

Effect of sodium to barium substitution on the space charge implementation in thermally poled glasses for nonlinear optical applications

Thermally poled niobium borophosphate glasses in the system 0.55(0.95−y) NaPO₃+y/2 Ba(PO₃)₂+0.05Na₂B₄O₇)+0.45Nb₂O₅ were investigated for second order optical nonlinear (SON) properties. Bulk glasses were studied by Raman spectroscopy, thermal analysis, optical and dielectric measurements. The sodium to barium substitution does not lead to significant changes in optical properties, crystallization of glasses and coordination environment of polarizable niobium atoms. However, the ionic conductivity decreases drastically with the increase of barium concentration. Secondary ion mass spectroscopy has been used to determine the element distribution in the anode layer of the thermally poled glasses. The second order optical susceptibilities gradually decrease from χ⁽²⁾=2.8 pm/V to zero with the increase of barium content. Using a simple electrical model, variations of nonlinear optical responses have been correlated with dielectric characteristics.     

Ionic Mobility in Glasses in the ZrF4-BiF3-MF Systems (M = Li,Na, K) as Probed by 7Li, 19F,and 23Na NMR

The ion mobility in new fluoride glasses (mol %) 45ZrF₄ · 25BiF₃ · 30MF (I) (M = Li, Na, K), (70 - x)ZrF₄ · xBiF₃ · 30LiF (II) (15 ≤ x ≤ 35), and 45ZrF₄ · (55-x)BiF₃ · xMF (III) (M = Li, Na; 10 ≤ x ≤ 30) has been studied by ⁷Li, ¹9F, and ²³Na NMR in the temperature range 250–500 K. The character of ion motion in bismuth fluorozirconate glasses I and III is determined by temperature and the nature and concentration of an alkali-metal cation. Major type of ion mobility in glasses I–III at temperature 400–440 K are local motions of fluorine-containing moieties and diffusion of lithium ions (except for the glass with x = 10). The factors responsible for diffusion in the fluoride sublattice of glasses I have been determined. Sodium ions in glasses I and III are not involved in ion transport.     

Ta2O5 Nanocrystals Strengthened Mechanical,Magnetic, and Radiation Shielding Properties of Heavy Metal Oxide Glass

In this study, for the first time, diamagnetic 5d⁰ Ta⁵⁺ ions and Ta₂O₅ nanocrystals were utilized to enhance the structural, mechanical, magnetic, and radiation shielding of heavy metal oxide glasses. Transparent Ta₂O₅ nanocrystal-doped heavy metal oxide glasses were obtained, and the embedded Ta₂O₅ nanocrystals had sizes ranging from 20 to 30 nm. The structural analysis of the Ta₂O₅ nanocrystal displays the transformation from hexagonal to orthorhombic Ta₂O₅. Structures of doped glasses were studied through X-ray diffraction and infrared and Raman spectra, which reveal that Ta₂O₅ exists in highly doped glass as TaO₆ octahedral units, acting as a network modifier. Ta⁵⁺ ions strengthened the network connectivity of 1–5% Ta₂O₅-doped glasses, but Ta⁵⁺ acted as a network modifier in a 10% doped sample and changed the frame coordination units of the glass. All Ta₂O₅-doped glasses exhibited improved Vicker’s hardness, magnetization (9.53 × 10⁻⁶ emu/mol), and radiation shielding behaviors (RPE% = 96–98.8%, MAC = 32.012 cm²/g, MFP = 5.02 cm, HVL = 0.0035–3.322 cm, and Z_eff = 30.5) due to the increase in density and polarizability of the Ta₂O₅ nanocrystals.     

Fluorescence of Eu3+-doped InF3-based optical glasses

This paper reports physical, absorption and photoluminescence spectral properties of Eu³⁺-doped indium trifluoride-based optical glasses of the following formulae: 48 InF₃-24 BaF₂-7 AlF₃-20 RF, where RF is the alkali content (LiF, NaF and KF). From fluorescence characteristics of these Eu³⁺-doped glasses, it is found that Glass-A with 20 M% LiF as the network modifier shows a better trend in its optical behaviour. A red emission from these glasses has been noticed upon illumination with the UV lamp. The lifetimes of the lasing transition (⁵D₀→⁷F₂) have been measured both at 300 and 77K with an Ar⁺ laser (487.9 nm) as the source of excitation. Four additional fluorescent levels at 580, 592, 598 and 653 nm have also been measured.     

Synthesis and nonlinear optical properties of BaTi(BO3)2 and Ba3Ti3O6(BO3)2 crystals in glasses with high TiO2 contents

The ternary BaO-TiO₂-B₂O₃ glasses containing a large amount of TiO₂ (20-40 mol%) are prepared, and their optical basicities (Λ), the formation, structural features and second-order optical nonlinearities of BaTi(BO₃)₂ and Ba₃Ti₃O₆(BO₃)₂ crystals are examined to develop new nonlinear optical materials. It is found that the glasses with high TiO₂ contents of 30-40 mol% show large optical basicities of Λ=0.81-0.87, suggesting the high polarizabity of TiO_n polyhedra (n=4-6) in the glasses. BaTi(BO₃)₂ and Ba₃Ti₃O₆(BO₃)₂ crystals are found to be formed as main crystalline phases in the glasses. It is found that BaTi(BO₃)₂ crystals tend to orient at the surface of crystallized glasses. The new XRD pattern for the Ba₃Ti₃O₆(BO₃)₂ phase is proposed through Rietvelt analysis. The second harmonic intensities of crystallized glasses were found to be 0.8 times as large as α-quartz powders, i.e., I^2ω(sample)/I^2ω(α-quartz)=0.8, for the sample with BaTi(BO₃)₂ crystals and to be I^2ω(sample)/I^2ω(α-quartz)=68 for the sample with Ba₃Ti₃O₆(BO₃)₂ crystals. The Raman scattering spectra for these two crystalline phases are measured for the first time and their structural features are discussed.     

Third- and second-order optical nonlinearity of Ge-Ga-S-PbI2 chalcohalide glasses

Two series of metal iodide doped chalcohalide glasses (100−2x)GeS₂·xGa₂S₃·xPbI₂ (0?x?20) and (100−x)(0.8GeS₂·0.2Ga₂S₃)·xPbI₂ (0?x?15) were prepared and characterized. The microstructure of these glasses has been studied by Raman scattering spectra. Utilizing femtosecond time-resolved optical Kerr effect (OKE) technique at the wavelength of 820 nm, a largest third-order nonlinearity χ⁽³⁾ of 2.07×10⁻¹³ esu was obtained for the 90GeS₂·5Ga₂S₃·5PbI₂ glass, and it decreases with the addition of PbI₂ in both two series. After thermally poled, second-harmonic generation (SHG) has been observed in these glasses according to Maker fringe method and a large second-order nonlinearity χ⁽²⁾ as well as 4 pm/V was obtained for the 70GeS₂·15Ga₂S₃·15PbI₂ glass. The variations of χ⁽²⁾ and χ⁽³⁾ on glass composition are ascribed to the evolution of micro-structural units in glass. These novel chalcohalide glasses would be expected to be the promising candidate materials for nonlinear optical devices.     

Structural and spectroscopic investigations on Eu3+-doped alkali fluoroborate glasses

Eu³⁺-doped alkali fluoroborate glasses B₂O₃–XCO₃–NaF–Eu₂O₃ (where X = Li₂, Na₂, K₂, and Ca, Mg) have been prepared using the conventional melting technique and their structural and optical properties have been evaluated. The XRD pattern of the glasses confirmed the amorphous nature and the FTIR spectra reveal the presence of BO₃ and BO₄ units as their local structures along with the strong OH^? groups. From the absorption spectra the bonding parameters have been calculated and confirmed that the Eu–O bonds in the studied glasses are of covalent nature. Judd–Ofelt (JO) analysis has been carried out from the emission spectra. The JO parameters have been used to calculate transition probabilities (A), lifetime (τ_R) and branching ratios (β_R) and peak stimulated emission cross-section (σ_P^E) for the ⁵D₀ → ⁷F_J (J = 1, 2, 3 and 4) transitions of the Eu³⁺ ions. The decay from the ⁵D₀ level of Eu³⁺ ions in the title glasses has been measured and analysed. The lifetime of the ⁵D₀ level is found to be shorter than the reported glasses which may be due to the presence of OH^? groups.     

A magic-angle spinning 31P NMR investigation of crystalline and glassy inorganic phosphates

³¹NMR spectra of several inorganic phosphates have been examined both in the crystalline and the glassy states. The parameter (Z_eff/r)q clearly demarcates ortho-, pyro- and meta-phosphates in terms of the ³¹P chemical shifts. Based on such a diagram, inorganic phosphate glasses are found to consist essentially of metaphosphate units. NMR resonance of the glasses are generally much broader than those of crystalline phosphates.     

Influence of the molecular weight of polystyrene on its thermodynamic properties

The thermodynamic properties of a series of polystyrene samples with different molecular weights (M _w was varied from 2.5·10³ to 6.57·10⁴) were studied by precision adiabatic vacuum, high-accuracy dynamic, and combustion calorimetry: temperature dependences of the heat capacity in a wide temperature range, thermodynamic characteristics of glass transition and glassy state under standard pressure, and energy of combustion. The thermodynamic functions C ^○ _p (T), H ^○(T) - H ^○(0), S ^○(T) - S ^○(0), and G ^○(T) - H ^○(0) of polystyrene with different molecular weights, enthalpies of combustion Δ_c H ^○, thermodynamic parameters of formation from simple substances Δ_f H ^○, Δ_f S ^○, and Δ_f G ^○ at T = 298.15 K, and parameters of their synthesis from monomers were calculated from the experimental data. The temperature dependences of the heat capacity for a region of 0–380 K, glass transition temperatures, and thermodynamic characteristics of formation and synthesis of polystyrene depending on its molecular weight were examined.     

Electrical conductivity of porous glasses saturated with sulfuric acid solutions

Electrical conductivity of porous glasses saturated with sulfuric acid solutions was studied. At impregnating solution concentrations in the range 20–40 wt %, the glasses have high conductivities a σ > 0.1 ω^?1 cm^?1. The dependences of the electrical conductivity on parameters of the porous structure of membranes are considered.     

White light emission from Tm/Dy co-doped oxyfluoride germanate glasses under UV light excitation

In this paper, we report on the absorption and photoluminescence properties of Tm³⁺/Dy³⁺ ions co-doped oxyfluoride germanate glasses for white light emission. The X-ray diffraction (XRD) and differential thermal analysis (DTA) profiles of the host glass have been carried out to confirm its structure and thermal stability. From the measured absorption spectra, Judd-Ofelt (J-O) intensity parameters (Ω₂, Ω₄ and Ω₆) have been evaluated for Tm³⁺ and Dy³⁺ ions. A combination of blue, yellow and red emissions has emerged in these glasses, which allows the observation of bright white light when the glasses are excited by the ultraviolet light. The white light luminescence colour could be changed by varying the excitation wavelength. Also, various colours of luminescence, including white light, can be easily tuned by adjusting the concentrations of Tm³⁺ or Dy³⁺ ions in the co-doped glasses. Concentration quenching effect was also investigated and possible energy transfer mechanism from Dy³⁺→Tm³⁺ ions was explained which is also confirmed by the decay lifetime measurements.     

Electrical properties of LiBBaTe glass doped with Nd2O3

The dc and ac electrical conductivity of barium tellurite borate glass doped with Nd₂O₃ in the composition 50 B₂O₃- (20-X) BaO- 20TeO₂ 10 LiF or Li₂O where x = 0.5, 1, 1.5 and 2 Nd₂O₃ were measured in the temperature range 303–648 K and in the frequency range 0.1–100 kHz. The dc and ac conductivities values increase, whereas the activation energy of conductivities decreases with increasing Nd₂O₃ content in the glasses containing LiF and by the replacement of LiF by Li₂O the conductivity was found to decrease with addition of Nd₂O₃. The electrical conduction has been observed to be due to small polaron hopping at high temperatures. The frequency dependence of the ac conductivity follows the power law σ_AC (ω) = A ω^s. The frequency exponent (s) values (in the range 0.94 and 0.33) decreases with increasing temperature. The dielectric constant and dielectric loss increased with increasing temperature and decreased with increase in frequency for all glasses studied. In LiF glasses, it is observed that, the values of ?^\ and tan δ are observed to increase with the addition of Nd₂O₃ whereas they decrease in the glasses containing Li₂O. The electrical modulus formalism has been used for studying electrical relaxation behavior in studied glasses. It is for first time that the Nd₂O₃ doped barium tellurite borate glasses have been investigated for dc and ac conductivities and dielectric properties over a wide range of frequency and temperature.     

Impedance spectroscopy of V2O5–Bi2O3–BaTiO3 glass–ceramics

The glasses within composition as: (80 − x)V₂O₅/20Bi₂O₃/xBaTiO₃ with x = 2.5, 5, 7.5 and 10 mol% have been prepared. The glass transition (T_g) increases with increasing BaTiO₃ content. Synthesized glasses ceramic containing BaTi₄O₉, Ba₃TiV₄O₁₅ nanoparticles of the order of 25–35 nm and 30–46 nm, respectively were estimated using XRD. The dielectric properties over wide ranges of frequencies and temperatures were investigated as a function of BaTiO₃ content by impedance spectroscopy measurements. The hopping frequency, ω_h, dielectric constant, ε′, activation energies for the DC conduction, E_σ, the relaxation process, E_c, and stretched exponential parameter β of the glasses samples have been estimated. The, ω_h, β, decrease from 51.63 to 0.31 × 10⁶ (s⁻¹), 0.84 to 0.79 with increasing BaTiO₃ respectively. Otherwise, the E_σ, increase from 0.279 to 0.306 eV with increasing BaTiO₃. The value of dielectric constant equal 9.5·10³ for the 2.5BaTiO₃/77.5V₂O₅/20Bi₂O₃ glasses-ceramic at 330 K for 1 KHz which is ten times larger than that of same glasses composition. Finally the relaxation properties of the investigated glasses are presented in the electric modulus formalism, where the relaxation time and the respective activation energy were determined.