Optical properties of lead-bismuth cuprous glasses

The optical transmission and absorption spectra in UV- VIS were recorded in the wavelength range 350–800 nm for different glass compositions in the system (CuO) _x (PbO) ₅₀−x(Bi₂O₃)₅₀ (x = 2.5, 5.0, 7.5, 10.0, 12.5, 15.0, 20.0). Absorption coefficient (α), optical energy gap (E_opt), refractive index (n_D), optical dielectric constant (ε′_∞), measure of extent of band tailing (ΔE), constant (β) and ratio of carrier concentration to the effective mass (N/m*) have been reported. The effects of compositions of glasses on these parameters have been discussed. It has been indicated that a small compositional modification of the glasses lead to an important change in all the optical properties including non-linear behaviour. The optical parameters were found to be almost the same for different glasses in the same family.     

Optical properties of zinc–vanadium glasses doped with samarium trioxide

Zinc–vanadium glasses doped with samarium oxide having the chemical composition Sm₂O_3(x) ZnO_(40?x) V₂O₅₍₆₀₎(where x = 0?1–0?5 mol%) were prepared by melt quenching method. The density of these glasses was measured by Archimedes method; the corresponding molar volumes have also been calculated. The values of density range from 3?7512 to 5?0535 gm/cm³ and those of molar volume range from 28?3004 to 37?6415 cm^?3. The optical absorbance studies were carried out on these glasses to measure their energy bandgaps. The absorption spectra of these glasses were recorded in UV–Visible region. No sharp edges were found in the optical spectra, which verify the amorphous nature of these glasses. The calculated optical bandgap energies of these glasses were found to be in the range of 0?3173–0?6640 eV. The refractive index and polarizability of oxide ion have been calculated by using Lorentz–Lorentz relations. The values of refractive index range from 1?1762 to 1?2901 and those of polarizability of oxide ion range from 1?6906 × 10^?24 to 2?2379 × 10 ^?24cm³.     

Thermal and optical properties of zinc halotellurite glasses

Zinc halotellurite glasses were studied with respect to the glass transition, softening temperature, thermal expansion, optical energy gap, Urbach energy, density, molar volume, refractive index, polarizability, molar refraction and third order non-linear optical susceptibility. Thermal characteristic were determined using a dilatometry. The optical absorption in the wavelength range (300–3200 nm) was measured. From the absorption edge studies, the values of optical band gap (E _opt) and Urbach energy (ΔE) have been evaluated. Optical parameters viz., color dispersion, dispersion energy, E _d, average oscillator energy, E ₀, and third order non-linear optical susceptibility values are estimated from measuring the refractive index at different wavelength. Results obtained are discussed in terms of the glass structure.     

Optical investigation of a—Ga x Se100–x thin films

Abstract

The optical band gap and optical constants have been studied as a function of photon energy for a-Ga _x Se_100–x thin films (where x × 0, 2.5, 5.0, 7.5 and 10.0) in the wavelength region 450–1000 nm. The optical band gap decreases with the increase of Ga concentration in the a-Ga _x Se_100–x system. The refractive index (n) decreases while the extinction coefficient (k) increases with increasing photon energy. The results are interpreted in terms of concentration of localized states.     

Spectroscopic ellipsometry studies of amorphous PZT thin films with various Zr/Ti stoichiometries

Amorphous stoichiometric Pb(Zr _x Ti_{1 – x)}O₃) (PZT) thin films with various values of x were deposited on Si(100) substrates by the sol-gel technique. The influence of Ti content on the optical properties was studied by spectroscopic ellipsometry (SE) in the UV-visible region. Using a four-phase fitting model, the refractive index n and extinction coefficient k was obtained by analyzing the SE spectra. The optical band gap energies E _g for these films were reported under the assumption of a direct band-to-band transition. It has been found that the refractive index, extinction coefficient and band gap energy of the films were functions of the film compositions. The refractive index of the PZT films increases linearly with increasing Ti content. On the other hand, the optical band gap energy of the PZT films decreases with increasing Ti content.     

Optical absorption and electron spin resonance studies of Cu2+ in Li2O-Na2O-B2O3-As2O3 glasses

The local structure around Cu²⁺ ion has been examined by means of electron spin resonance and optical absorption measurements in xLi₂O-(40-x)Na₂O-50B₂O₃-10As₂O₃ glasses. The site symmetry around Cu²⁺ ions is tetragonally distorted octahedral. The ground state of Cu²⁺ isd _x ²−y ².The glass exhibited broad absorption band near infrared region and small absorption band around 548 nm, which was assigned to the ²B_1g →²E_g transition.     

Spectroscopic investigations of Cu2+ in Li2O-Na2O-B2O3-Bi2O3 glasses

Pure and copper doped glasses with composition,x Li ₂ O-(40-x)Na ₂ O-50B ₂ O ₃-10Bi ₂ O ₃,have been prepared over the range 0 ≤ x ≤ 40. The electron paramagnetic resonance (EPR) spectra of Cu²⁺ ions of these glasses have been recorded in the X-band at room temperature. Spin Hamiltonian parameters have been calculated. The molecular bonding coefficients, α² and β², have been calculated by recording the optical absorption spectra in the wavelength range 200–1200 nm. It has been observed that the site symmetry around Cu²⁺ ions is tetragonally distorted octahedral. The density and glass transition temperature variation with alkali content shows non-linear behaviour. The IR studies show that the glassy system contains BO₃ and BO₄ units in the disordered manner.     

Optical properties of lead-tellurite glasses doped with samarium trioxide

The optical properties of a new family of xSm₂O₃-(40-x)PbO-60TeO₂ glasses are investigated. The optical absorption spectra were recorded at room temperature in the UV-visible region. From the absorption edge studies, the values of optical bandgap energies have been evaluated. The refractive index, molar refraction and polarizability of oxide ions have been calculated by using Lorentz-Lorentz relations. The non-linear variations of the above optical parameters are discussed with respect to samarium concentration.     

Effect of NiO content on the optical band gap, refractive index, and density of TeO2–V2O5–NiO glasses

Amorphous layers and bulk glasses of 40TeO₂–(60 ? x)V₂O₅–xNiO compositions with 0 ≤ x ≤ 30 (in mol%) have been prepared using the usual blowing technique and press-melt quenching method, respectively. The optical absorption spectra of the layers have been recorded in the wavelength range 400–800 nm. The fundamental absorption edge has been identified from the optical absorption spectra. The optical band gap, width of the tail of the localized states, and refractive index have been evaluated using available theories. Results show that the values of optical band gap decrease from 2.02 to 1.64 eV as the contribution of NiO increases. The refractive index dispersion is fitted to the single oscillator model, and results show that the static refractive index increase from 1.309 to 1.673 as the NiO content increases. The glass transition temperature, density, and molar volume have been studied, indicating act of NiO as network modifier. Values of theoretical optical basicity are also reported.     

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.     

Optical band gap and optical constants in a-Se100–xSbx thin films

Abstract

The optical properties of a-Se_100-xSb_x thin films (where x = 0, 0.5, 2.5, 5 and 10) have been studied in the wavelength range 540–900 nm. It was found that the optical band gap increases with increasing Sb concentration in the a-Se_100-x Sb _x system. The refractive index n decreases, while the extinction coefficient k increases with increasing photon energy. DC conductivity measurements of a-Se_100-x Sb _x thin films have been reported in the temperature range 349–375 K. It has been observed that the conductivity increases while the activation energy decreases with increasing Sb concentration. We correlated the optical band gap with the electronegativity of the sample. The band gap increases with the decrease in electronegativity of each sample of a-Se_100-x Sb _x .     

Structure,electrical, and optical properties of ZnO-substituted PbO for the Er<Superscript>3+</Superscript>/Yb<Superscript>3+</Superscript> co-doped Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>–GeO<Subscript>2</Subscript>–Na<Subscript>2</Subscript>O glass system

Glasses of the 0.5Er³⁺/2.5Yb³⁺ co-doped (40Bi₂O₃–20GeO₂–(30 − x)PbO–xZnO–10Na₂O system where x = 0.0, 5, 10, 15, 20, 25, and 30 mol%) have been characterized by FT-IR spectroscopy measurements to obtain information about the influence of ZnO-substituted PbO on the local structure of the glass matrix. The density and the molar volume have been determined. The influences of the ZnO-substituted PbO on the structure of glasses have been discussed. The dc conductivity measured in the temperature range 475–700 K obeys Arrhenius law. The conductivity decreases while the activation energy for conduction increases with increase ZnO content. The optical transmittance and reflectance spectrum of the glasses have been recorded in the wavelength range 400–1100 nm. The values of the optical band gap E _opt for all types of electronic transitions and refractive index have been determined and discussed. The real and imaginary parts ε₁ and ε₂ of dielectric constant have been determined.     

Effect of tellurium addition on the optical and physical properties of germanium selenide glassy semiconductors

Thin films of the glasses Ge₁₀ Se_90−x Te_x (0 ≤ x ≥ 40) have been prepared by melt quenching technique; thin films were evaporated at a pressure of ≈10⁻⁴ Pa. The optical absorption behavior of these thin films was studied from the reflection and transmission spectrum in the spectral range 200-1200 nm. The optical constants i.e optical band gap (E_opt), absorption coefficient, refractive index (n) are calculated. The optical band gap has been estimated using Tauc extrapolation and found to decrease with Te content. The Dispersion of refractive index has been studied in terms of Wemple - Di Domenico model. The value of static refraction index has been found to increase with Te content. The distribution of the possible chemical bonds has been calculated. The obtained results were correlated with the character of the chemical bond for the prepared compositions through a study of parameters such as average heat of atomization (Hs), the cohesive energies of the bonds (CE), The mean bond energy <E> and average coordination number (m).     

Comprehensive comparison on optical properties of samarium oxide (micro/nano) particles doped tellurite glass for optoelectronics applications

Rare-earth oxides microparticles doped tellurite-based glass have been studied extensively to improve the capability of optoelectronic devices. We report a detailed comparison between two sets of glass series containing samarium microparticles and nanoparticles denoted as ZBTSm-MPs and ZBTSm-NPs, respectively. The two sets of glass have been successfully fabricated via melt-quenching technique with chemical formula {[(TeO₂)_0.70 (B₂O₃)_0.30]_0.7 (ZnO)_0.3}_1?y (Sm₂O₃ (MPs/NPs))_y with y?=?0.005, 0.01, 0.02, 0.03, 0.04 and 0.05 mol fraction. The TEM analysis confirmed the existence and formation of nanoparticles in ZBTSm-NPs glasses. The density of ZBTSm-NPs glasses was found higher than ZBTSm-MPs glasses due to the distributions of nano-scale particles in tellurite glass network. There was a linear trend of increment in the refractive index in both sets of glass series along with the concentrations of dopants. The refractive index of ZBTSm-NPs glasses was found higher than ZBTSm-MPs glasses due to the shift in compactness of glass structure with nano-scale particles. In comparison, the absorption peaks of ZBTSm-MPs glasses were greater than ZBTSm-NPs glasses which were mainly due to the restriction of electrons mobility in glass network with nano-scale particles. The optical band gap energy in ZBTSm-NPs glasses was found greater than ZBTSm-MPs glasses which correspond to the widening of forbidden gap with nano-scale particles. The polarizability of ZBTSm-NPs and ZBTSm-MPs was found in non-linear trends along with dopant concentrations. Based on these findings, the improvement of optical properties has been made by introducing samarium oxide nanoparticles in tellurite glass which is beneficial for optoelectronic devices.

     

Rings, chains and planes: Variation ofT g with composition in chalcogenide glasses

We propose a microscopic, phenomenological model for the decrease in the viscosity observed at glass transition. Our model is primarily applicable to chalcogenide glasses. According to this model, the decrease in the viscosity at glass transition is mainly due to the breaking of the Van der Waals bonds in the chalcogenides. Using this model, we derive a relationship between the glass transition temperature,T _g ,and the molar volume V _m.The validity of this relation is checked using experimental data available in the literature for two binary systems (Ge-Se and As-S) and a pseudo-binary system (As ₄₀ Se _x Te _60-x .     

Studies on boro cadmium tellurite glasses

To investigate the modification effect of the modifier CdO on boro tellurite glass, a series of glasses with compositions (50 − x) CdO-xTeO₂-50B₂O₃ have been prepared by conventional melt quenching technique. Optical absorption, IR and Raman structural studies are carried out on the glass system. The optical absorption studies revealed that the cutoff wave length and refractive index increase while optical band gap (E_opt) and Urbach energy decreases with increase of CdO content. The IR and Raman studies revealed that structure of glass network consists of [TeO_3]/[TeO₃₊₁], [TeO₄], [BO₃], [BO₄] and [Cd-Te] linkages .The compositional dependence of different physical parameters such as density, molar volume, oxygen packing density, optical basicity, have been analyzed and discussed.     

Optical properties of 60B2O3-(40-x)PbO-xMCl2 and 50B2O3-(50-x) PbO-xMCl2 (M = Pb, Cd) glasses

Optical absorption and transmittance spectra of 60B₂O₃-(40-x)PbO-xMCl₂ and 50B₂O₃-(50-x) PbO-xMCl₂ (M = Pb, Cd) (10 ≤x ≤ 20) glasses of varying composition were recorded in the UV-visible region. Various optical parameters such as optical energy gap (E _opt), Urbach energy (E _e), refractive index (n ₀), optical dielectric constant (ε∞), and ratio of carrier concentration to the effective mass (N/m*;) were determined. The variation of optical energy gap with increase in the concentration of PbCl₂ or CdCl₂ is discussed.     

Optical properties of (1-x-y)B2O3-xLi2O-yMCI2 (M=Cd, Zn) glasses

Optical absorption and transmission spectra of (1-x-y)B₂O₃-xLi₂O-yMCI₂ (M=Cd, Zn) glasses of varying compositions were recorded in the UV-visible region. From the spectra, various optical parameters such as optical energy gap (E _opt), refractive index (n), optical dielectric constant (ɛ′), width of the tail of localized states in the forbidden gap (ΔE), ratio of carrier concentration to the effective mass (N/m*) and the constantB were evaluated. The effects of composition of glasses on these parameters are discussed.     

Thermal and optical properties of tellurite glasses doped erbium

Er³⁺-doped tellurite glasses with molar compositions of 75TeO₂–20ZnO–(5 − x) Na₂O–xEr₂O₃ (x = 0, 0.5, 1, 2, 3, and 4 mol%) have been elaborated from the melt-quenching method. The effects of Er₂O₃ concentration on the thermal stability and optical properties of tellurite glasses have been discussed. From the differential scanning calorimetry (DSC) profile, the glass transition temperature T _g, and crystallization onset temperature T _x are estimated. The thermal stability factor, defined as ∆T = T _x − T _g, was higher than 100 °C. It suggests that tellurite glass exhibits a good thermal stability and consequently is suitable to be a potential candidate for fiber drawing. Furthermore, the stability factor increases with Er₂O₃ concentration up to 2 mol% then presents a continue decrease suggesting of beginning of crystallization of highly doped tellurite glasses. The refractive index and extinction coefficient data were obtained by analyzing the experimental spectra of tanΨ and cos∆ measured by spectroscopic ellipsometry (SE). The complex dielectric functions (ε = ε₁ + iε₂) of the samples were estimated from regression analysis. The fundamental absorption edge has been identified from the optical absorption spectra and was analyzed in terms of the theory proposed by Davis and Mott. The values of optical band gap for direct and indirect allowed transitions have been determined. An important decrease of the optical band gap was found after Er doping. It was assigned to structural changes induced from the formation of non-bridging oxygen. The absorption coefficient just below the absorption edge varies exponentially with photon energy indicating the presence of Urbach’s tail. The origin of the Urbach energy is associated with the phonon-assisted indirect transitions.     

Study of electrical properties of glassy Se100- xTexalloys

Temperature and frequency dependence of a.c. conductivity have been studied in glassy Se_100- x _Te x(x = 10, 20 and 30) over different range of temperatures and frequencies. An agreement between experimental and theoretical results suggests that the a.c. conductivity behaviour of selenium-tellurium system (Se_100- xTex)can be successfully explained by correlated barrier hopping (CBH) model. The density of defect states has been determined using this model for all the glassy alloys. The results show that bipolaron hopping dominates over single-polaron hopping in this glassy system. This is explained in terms of lower values of the maximum barrier height for single-polaron hopping. The values of density of charged defect states increase with increase in Te concentration. This is in agreement with our previous results obtained from SCLC measurements.