CsCl effect on the optical properties of the 80GeS2–20Ga2S3 base glass

Optical properties of chalcogenide glasses belonging to the series (80GeS₂–20Ga₂S₃)_100−x (CsCl) _x with x=0;5;10;15;20 were investigated. The linear refractive indices (n ₀) were determined by prism measurements at four wavelengths: 633 nm, 825 nm, 1311 nm, and 1511 nm. Z-scan experiments were performed at 800 nm to measure the non-linear indices (n ₂) and the absorption coefficients (β). CsCl additions in the base glass (80GeS₂–20Ga₂S₃) are characterized by a white shift of the transmission in the visible range and a strong decrease of both n ₀ and n ₂. As the same time, β is also decreasing and this results in a figure of merit FOM=2βλ/n ₂ that remains relatively low at 800 nm, meaning that this series of highly non-linear glasses should be very suitable for optical switching applications at telecommunication wavelengths.     

Controlled crystallization of β-In2S3 in 65GeS2⋅25In2S3⋅10CsCl chalcohalide glass

65GeS₂?25In₂S₃?10CsCl chalcohalide glass-ceramics containing β-In₂S₃ crystallites in the glassy matrix were prepared by traditional melt-quenching and subsequent heat-treatment at a fairly low temperature (T _g +10 ^°C) for different durations. The transmission spectra show that the cut-off edge of short wavelength is red-shifted with the prolongation of annealing time, but remains an excellent transmittance in the mid-IR region. Meanwhile, its crystallization behavior was investigated systematically. The results show that the precipitation of β-In₂S₃ crystal phase is responsible for the first crystallization peak, and the second crystal phase is GeS₂, which precipitated in the interior after a heat treatment at a high temperature (T _g +70 ^°C). Furthermore, the crystallization mechanism was investigated using the non-isothermal method. The crystallization rate constant K value of 6.08×10^?4 s^?1 at 346 ^°C for the β-In₂S₃ phase is about three times larger than that of the GeS₂ phase, indicating a much easier crystallization mechanism of β-In₂S₃ phase. Therefore, it is easy to control the precipitation of sole β-In₂S₃ crystallite, and to avoid interference of the second crystal phase GeS₂.     

Ultrafast non-resonant third-order optical nonlinearity of GeS2–Ga2S3–CdS chalcogenide glass

Ultrafast third-order nonlinear optical responses of 4(1?x)/5GeS₂-(1?x)/5Ga₂S₃-xCdS (x=0.05, 0.10 and 0.15 in mol%) chalcogenide glasses was investigated by using the femtosecond time-resolved optical Kerr effect technique at a wavelength of 800 nm. The largest third-order nonlinear susceptibility of all samples was estimated to be 1.65×10^?13 esu. An ultrafast nonlinear response time of about 250 fs was observed, which was dominantly assigned to the ultrafast distortion of the electron cloud under femtosecond laser excitation. A nonlinear relationship between the third-order nonlinear susceptibility and the introduced amount of CdS was discussed, suggesting a possible disturbance between different polarizable bonds in the glass system.     

IR impurity absorption in Sb2S3–GeS2(Ge2S3) chalcogenide glasses

The IR optical transmission spectra in the 4000–1000 cm⁻¹ (2.5–10 μm) region in the chalcogenide glasses (ChG) of the ternary Ge–Sb–S system of stoichiometric Sb₂S₃–GeS₂ and non-stoichiometric Sb₂S₃–Ge₂S₃ compositions are studied. The compositional dependences of the measured IR spectra connected with influence of O-, H- and C-based absorbed impurites are analyzed.     

Crystallization kinetics of the TeO2–BaO glass system

Tellurite glasses of the system (100–x)TeO₂–xBaO, with x = 05, 10, 15 and 20 wt%, have been prepared and studied by differential scanning calorimetry (DSC). The crystallization kinetics of the glasses were investigated under non-isothermal conditions, applying the formal theory of transformations for heterogeneous nucleation to the experimental data obtained by DSC, using continuous-heating techniques. In addition, from the dependence of the glass-transition temperature (T _g) on heating rate, the activation energy for the glass transition was derived. Similarly, the activation energy of the crystallization process was determined and the crystallization mechanism characterized. The thermal stability of these glasses are considered in terms of the characteristic temperatures, T _g and T _in (the onset temperature of crystallization), via ΔT = T _in?T _g and a kinetic parameter K(T _g). The results confirm that thermal stability decreases with increasing BaO content. The phases into which the glass crystallizes have been identified by X-ray diffraction. Diffractograms of the transformed material indicate the presence of microcrystallites of α-TeO₂, γ-TeO₂ and BaTeO₃ in the remaining amorphous matrix.     

Measurement of borneol based on infrared spectrometry

The infrared spectrometry contains multiple information of the sample, and it is easy to be applied to online measurement. To Chinese medicine, this technology can improve the standard of quality control and accelerate the modernization course. In this paper, we investigate the spectral characteristics of borneol, an effective ingredient in many Chinese medicines. The following results are achieved. In middle infrared (MIR) region, utilizing the linear relationship between absorption and concentration, the concentration of borneol with relative error within 4.30% in the strongest absorption region (2950 - 2970 cm-1) is measured; in near infrared (NIR) region, the predicted concentrations of borneol are calculated by using partial least squares (PLS) regression analysis, in which the wavelengths are selected by genetic algorithm (GA) from the absorption bands of borneol in NIR region. The predicted relative error of calibration model is less than 2%. This result shows that PLS regression analysis combinin     

Concept of infrared photodetector based on graphene–graphene nanoribbon structure

We study the mechanisms of photoconductivity in graphene layer–graphene nanoribbon–graphene layer (GL–GNR–GL) structures with the i-type gapless GL layers as sensitive elements and I-type GNRs as barrier elements. The effects of both an increase in the electron and hole densities under infrared illumination and the electron and hole heating and cooling in GLs are considered. The device model for a GL–GNR–GL photodiode is developed. Using this model, the dark current, photocurrent, and responsivity are calculated as functions of the structure parameters, temperature, and the photon energy. The transition from heating of the electron–hole plasma in GLs to its cooling by changing the incident photon energy can result in the change of the photoconductivity sign from positive to negative. It is demonstrated that GL–GNR–GL photodiodes can be used in effective infrared and terahertz detectors operating at room temperature. The change in the photoconductivity sign can be used for the discrimination of the incident radiation with the wavelength 2–3 μm and 8–12 μm.     

Effects of CeO_2 and nano-ZrO_2 agents on the crystallization behavior and mechanism of CaO–Al_2O_3–MgO–SiO_2-based glass ceramics

The crystallization behavior and mechanism of CaO–Al_2O_3–MgO–SiO_2(CAMS)-based diopside glass ceramics with nano-ZrO_2 nucleators and CeO_2 agents have been investigated.The use of nanoscale ZrO_2 as nucleators is favorable to the crystallization of glass ceramic at a relatively lower temperature due to the reduction of the activation energy, while the activation energy is increased after adding the CeO_2 agent.The microstructure and orientation have been analyzed by scanning electron microscopy and electron backscatter diffraction.Two discernible layers are observed, featured in glass and crystalline phases, respectively.Remarkably textured polycrystalline diopsides are verified for the samples(A and B)free of CeO_2 agents, with c-axes perpendicular to the interface of the two layers.Comparatively, the c-axes of diopside grains of the sample(C) with CeO_2 agents are proved to be parallel to the interface.Nanocrystals are detected in the vicinity of the interface for sample C.     

Investigations on ultrafast welding of glass–glass and glass–silicon

Using ultrafast laser radiation glass substrates are welded with glass and silicon plates. The pump beam is focused by a microscope objective with large NA=0.4 (beam diameter 4 μm) into the glass. After partial absorption of the optical energy, the glass is heated and melted. Procedures for high-quality welding of glass–glass and glass–silicon substrates with high-repetition ultra-fast laser radiation have been derived at the repetition rate 700 kHz. The dependencies of the dimension and geometry of the welding seam on scan velocity, repetition rate and pulse energy have been investigated defining a process window. Adding a noninterferometric technique for quantitative phase detection with the welding setup, the interaction zone of the welding seam for the welding partners glass–glass is detected. A change in refractive index is induced by heating and compression of the glass and has been detected by phase detection up to 2 μs after irradiation with 100 fs time resolution.     

Crystallization and conductivity of 2CaO–La2O3–5P2O5 glass–ceramic with Al2O3 addition

Al₂O₃ was added to a 2CaO–La₂O₃–5P₂O₅ metaphosphate, to replace 10% of the Ca²⁺ ions by Al³⁺, forming a phosphate with the nominal composition 1.8CaO–0.1Al₂O₃–La₂O₃–5P₂O₅. The effect of Al₂O₃ addition and heat treatment on the microstructure and conductivity of the resulting glass–ceramics was investigated by XRD, SEM, TEM, and AC impedance spectroscopy. Upon transformation from glass to glass–ceramic, conductivities increased significantly. The glasses were isochronally transformed at 700 and at 800 °C for 1 h or 5 h, in air, following heating at 3 or 10 °C/min. With Al₂O₃ addition, after a heat treatment at 700 °C, 100–300 nm nano-domains of LaP₃O₉ crystallized from the glass matrix. Annealing at 800 °C produced a further order of magnitude conductivity increase for the Al-free glass, but less so for the Al-containing glass.     

Induced crystallization and the physical properties of PbO–Sb2O3–As2O3: MoO3 glass system

PbO–Sb₂O₃–As₂O₃ glasses mixed with different concentrations of MoO₃ (ranging from 0 to 1.0 mol%) were crystallized. The samples were characterized by X-ray diffraction, scanning electron microscopy and differential thermal analysis techniques. The X-ray diffraction and the scanning electron microscopic studies have revealed the presence of Pb₅Sb₂O₈, PbSb₂O₆, SbAsO₄, Sb₂MoO₆, Sb₄Mo₁₀O₃₁, As₄Mo₃O₁₅, Pb₅Sb₄O₁₁ crystalline phases in these samples. The differential thermal analysis indicated that the surface crystallization prevails over the bulk crystallization as the concentration of the crystallizing agent is increased. The infrared (IR) spectral studies exhibit bands due to MoO₄ structural units in addition to the conventional bands due to various antimonate and arsenate structural groups. The studies on PbO–Sb₂O₃–As₂O₃: MoO₃ glass-ceramics with respect to various physical properties viz., dielectric properties over a range of frequency and temperature, optical absorption, electron spin resonance (ESR) and magnetic susceptibility at room temperature have also been reported. The optical absorption, ESR and magnetic susceptibility studies indicated that the molybdenum ions exist in Mo⁵⁺ state in addition to Mo⁶⁺ state in these samples. The redox ratio found to increase as the concentration of the MoO₃ is increased. The variations observed in all these properties with the concentration of the crystallizing agent have been analyzed in the light of different oxidation states and environment of molybdenum ions in the glass ceramic network.     

Super-linear frequency dependence of ac conductivity of disordered Ag2S–Sb2S3 at cryogenic temperatures

The ac conductivity of a new class of disordered solids, i.e. mechanochemically synthesized amorphous fast ion conducting Ag₂S–Sb₂S₃ materials, has been investigated in the audio frequency range (10–10⁷?Hz) down to cryogenic temperatures (～10?K). The conductivity spectra exhibit the usual signature of a disordered system at higher temperatures, well described by the Jonscher power law (JPL) i.e., σ′(ω)?=?σ _dc?+?A(T)ω*, although the frequency exponent (n?<?1) is found to be a weak function of temperature. However, as the temperature is lowered, the frequency width of the σ _dc region decreases gradually and that of the JPL region increases. Eventually, the σ _dc region disappears and the JPL region alone dominates the spectrum. However, at the lowest temperatures, both the σ _dc and JPL regions disappear and σ′(ω) obeys a super-linear power law (SPL) (σ′?∝?ω^m , m?≥?1). It is observed that the SPL has strikingly similar characteristics to the well-established nearly-constant-loss (NCL) behaviour corresponding to m?=?1. Both SPL and NCL appear in the same time–temperature (low-temperature/low-frequency) domain. Furthermore, in both cases the conductivity is a distinctly weak function of temperature but quite sensitive to frequency, and the SPL/NCL?→?JPL crossover frequency is thermally activated with almost the same energy as the ac activation energy. The presence of the SPL is further manifested in the form of a well-defined minimum in the dielectric loss, ε″(ω), spectra. It is therefore proposed that the entire low-temperature/low-frequency spectra can be described by a modified Jonscher power law, σ′(ω)?=?σ _dc(T)?+?A(T) ωⁿ ?+?B(T)ω^m , m?=?1 (NCL), m?>?1 (SPL), where the second term with n?<?1 accounts for the JPL and the third term with m?≥?1 accounts for SPL/NCL. The results and some other low-temperature/low-frequency conductivity data are consistent with an asymmetric double well potential (ADWP) model.     

Structure, phase formation, and wetting behavior of BaO–SiO2–B2O3 based glass–ceramics as sealants for solid oxide fuel cells

In the present study, glasses from the three different compositional triangles in the BaO–B₂O₃–SiO₂ system with fixed B₂O₃/SiO₂ ratio and different BaO/SiO₂ molar ratios (designated as Ba32, Ba37, and Ba42) were prepared, and suitability of them as sealant in solid oxide fuel cells were investigated. Structure of the glasses was characterized with Raman spectroscopy. According to the results, the structure of the glass with 32 % molar BaO (Ba32) predominantly consisted of Q² structural species. In glasses with 37 and 42 % molar BaO (Ba37 and Ba42), with the substitution of SiO₂ by BaO, distribution of Qⁿ units widened, silicate glass network depolymerized, and concentration of Q¹ structural units increased at the expense of Q² units. X-ray diffraction analyses revealed that in samples Ba32 and Ba37, initially, Ba₃Si₅O₁₃ and Ba₅Si₈O₂₁ phases were crystallized, respectively, and it seemed they acted as the sites for the subsequent growth of BaSi₂O₅ phase. In contrast, the dominant phase in sample Ba42 was Ba₂Si₃O₈. Sintering, wetting, and crystallization behavior of the glasses were studied using hot-stage microscopy and differential thermal analysis, respectively. Delay in the crystallization accompanied by depolymerization of the structure led into deformation at lower temperatures and greater wettability on the steel for Ba37 glass. All the glasses wetted AISI430 alloy at temperatures higher than 1,000 °C.     

Influence of iron ions on dielectric properties of the PbO–Bi2O3–B2O3 glass system

PbO–Bi₂O₃–B₂O₃ glasses containing small concentrations of Fe₂O₃ (0–1 mol%) were subject to dielectric studies (dielectric constant ε′; loss tan δ; and ac conductivity σ _ac) over a wide range of frequency and temperature. From spectroscopic (infrared, optical absorption and ESR spectra) and magnetic susceptibility studies, variations in these properties with dopant ion concentration were analyzed in terms of different oxidation states and iron ion environment in the glass network.     

PAC study on the thermal evolution of the 60ZrF4–40BaF2 glass

By using ¹⁸¹Ta probes, the PAC technique has been used to investigates the behaviour of the hyperfine interaction in 60ZrF₄–40BaF₂ glass from room temperature (RT) up to the glass temperature T_g (562 K). A first serie of measurements was obtained while heating the as-prepared sample from RT to T_g. A second serie was performed on the as-treated sample after cooling it down to RT and again heated to T_g. In both series the same three components of the quadrupole interaction were observed. Dynamical effects were detected in the main component and activation energies of 0.18₁ eV and 0.21₃ eV were obtained. The results are interpreted as dynamical effects associated to the movement in the fluorine ions during polyhedra rearrangements. This revised version was published online in August 2006 with corrections to the Cover Date.     

Results of the Experiments on the Crystallization of a Ge–Si–Sb Solid Solution under the Conditions of Microgravity on the Soyuz–Apollo Spacecraft

Physics of the Solid State - Objective factors that allow the experiment on growing crystals of a Ge–Si–Sb solid solution on the Soyuz–Apollo spacecraft to take a special place...     

Thermal analysis and infrared study of Nb2O5–TeO2 glasses

Tellurite glasses of the xNb₂O₅–(100–x) TeO₂, (3 ≤ x ≤ 20 mol%) system have been prepared and studied by IR spectroscopy and differential thermal analysis to explore the role of Nb₂O₅ on their structure. IR analysis indicates that NbO₆ transforms TeO₄ units into tellurite structural TeO₃ units, with a shift of lattice vibrations towards higher wavenumbers. The stretching force constant of the tellurite structural units increases with Nb₂O₅ content, a feature that is attributed to the higher bond strength and higher coordination number of Nb₂O₅ relative to TeO₂. The crystallization kinetics has been studied under non-isothermal conditions using the formal theory of transformations for heterogeneous nucleation. The crystallization results are analyzed, and both the activation energy of the crystallization process and the crystallization mechanism are characterized. The thermal stability of these glasses are characterized in terms of characteristic temperatures, such as the glass-transition temperature, T _g, the temperature of onset of crystallization, T _in, the temperature corresponding to the maximum crystallization rate, T _p, and two kinetic parameters, K(T _g) and K(T _p). The results reveal that thermal stability increases with increasing Nb₂O₅ content. XRD diffraction of the studied glasses indicates the presence of microcrystallites of α-tellurite, γ-telluride, Nb₂Te₄O₁₃ and an amorphous matrix.     

Effect of replacement of Se by S on structural and physical properties of Ge–Sb–As–Se–S chalcogenide glasses

In the present study, the structural and opto-mechanical properties of Ge–Sb–As–Se–S chalcogenide glasses have been investigated. For this purpose, different bulk glasses of Ge₂₀Sb₅As₁₅Se_60?xS_x (0 ≤ x≤50) were prepared by conventional melt quenching technique in quartz ampoule and different characteristics of prepared glasses such as glass transition temperature, density, hardness, transmittance, optical band gap energy and refractive index were determined. The value of hardness and glass transition temperature of prepared glasses were found to increase with increasing the sulfur content as a result of formation of GeS₄ tetrahedral units and increasing the network connectivity and average bonding energy. The optical energy gap (according to Tauc’s relation), transmittance and refractive index of prepared glasses are in direct relation with sulfur content. In this study, the highest value of transmittance (about 70%) and lowest value of refractive index (2–2.3) was achieved in Ge₂₀Sb₅As₁₅Se₄₀S₂₀ and Ge₂₀Sb₅As₁₅Se₁₀S₅₀ glasses, respectively.