Investigations on spectral features of tungsten ions in sodium lead alumino borate glass system

Na₂O–PbO–Al₂O₃–B₂O₃ (NPAB) glasses mixed with different concentrations of WO₃ (ranging from 0 to 2.5 mol%) are synthesized by conventional melt quenching method. The samples are characterized by X-ray diffraction (XRD), optical absorption, Electron paramagnetic resonance (EPR) and Fourier transform infrared (FT-IR) spectroscopic techniques. Glass formation is confirmed by X-ray diffraction spectra. The optical absorption spectra of these glasses exhibited a predominant broad band peak at about 850–870 nm is identified due to d_xy–d_x²_−y² transition of W⁵⁺ ions. From the optical absorption spectral data, optical band gap (E_opt) and Urbach energy (ΔE) are evaluated. From EPR spectra the strength of the signal is increased and hyperfine splitting is resolved with increasing concentration of WO₃ in the glass matrix. The FT-IR spectral studies have pointed out the existence of conventional BO₃, BO₄, B–O–B, PbO₄, WO₄ and WO₆ structural units of these glasses. Various physical properties and optical basicity are also evaluated with respect to the concentration of WO₃ ions.     

IR and Raman investigation on the structure of (100-x)B2O3-x[0.5 BaO-0.5 ZnO] glasses

Glasses with molar composition of (100-x)B₂O₃-x[0.5 BaO-0.5 ZnO], x=40, 50, 60, 70 were prepared from the melts of ZnO, BaCO₃ and H₃BO₃ mixture. The structure and thermal behavior were characterized by IR and Raman spectroscopy, DSC and Dilatometer. The investigation shows that the transition of the structural unit [BO₄] (B^IV) to [BO₃] (B^III) happens when BaO and ZnO content x increases in the borate glass, resulting in fewer B^III-O-B^IV bonds and more B^III-O-B^III bonds. At the same time, the diborate groups, which are found to be the predominant structural group of the glass with high B₂O₃ content, gradually changes into ring-type metaborate, pyro- and orthoborate groups. With increasing ZnO and BaO content x, the glass transition temperature (T_g) and the softening point (T_f) decreases, while linear expansion coefficient (α) increases, that comes from the weakening of the glass network.     

Spectral studies on Cu ions in sodium–lead borophosphate glasses

Electron Paramagnetic Resonance (EPR) and optical absorption spectra of Cu²⁺ ions in sodium–lead borophosphate glasses doped with different concentrations of Cu²⁺ ions have been studied. EPR spectra of all the glass samples exhibit resonance signals characteristic of Cu²⁺ ions. The values of spin-Hamiltonian parameters indicate that the Cu²⁺ ions in sodium–lead borophosphate glasses are present in octahedral sites with tetragonal distortion. The optical absorption spectra of all the glass samples show a single broad band, which has been assigned to the ²B_1g→²B_2g transition of Cu²⁺ ions. The optical band gap energy (E_opt) and Urbach energy (ΔE) are calculated from their ultraviolet absorption edges. The emission bands observed in the ultraviolet and blue region are attributed to 3d⁹4s→3d¹⁰ triplet transition in Cu⁺ ion. The FT-IR spectra show that the glass system contains BO₃, BO₄ and PO₄ structural units.     

Optical properties of glasses in the Li2O–MoO3–P2O5 system

Glasses xLi₂O–(50-x)(MoO₃)₂–50P₂O₅ with x = 10, 20, 30, and 40 mol% were prepared and their optical and electrical properties were investigated. Analysis of the IR spectra revealed that the Li⁺ ions act as a glass modifier that enter the glass network by breaking up other linkages and creating non-bridging oxygens in the network. The optical absorption edge of the glasses was measured for specimens in the form of thin blown films and the optical absorption spectra of those were recorded in the range 200–800 nm. From the optical absorption edges studies, the optical band gap (E _opt) and the Urbach energy (E _e) values have been evaluated by following the available semi-empirical theories. The linear variation of (αhν)^1/2 with hν, is taken as evidence of indirect interband transitions. The E _opt values were found to decrease with increasing Li₂O content by causing increase in the number of non-bridging oxygens in network. The Urbach tail analysis gives the width of localized states between 0.48 and 0.74 eV.     

Evolution of ferroelectric SrBi2Nb2O9 phase embedded in tellurite glass

Glasses with the composition, [(100-x)TeO₂- x(SrO–Bi₂O₃–Nb₂O₅)] with x = 20, 30 and 40 (in mol %) were prepared. The X-ray diffraction (XRD) pattern and differential thermal analysis (DTA) for the as-prepared samples confirmed the amorphous and glassy characteristics, respectively. The SrBi₂Nb₂O₉ phase in tellurite glass for HT773 sample at x = 40 mol % is formed and confirmed by the Rietveld refinement. DTA curves for all glass samples exhibit two endothermic dips while the two broad exothermic peaks at lower x reduced to one at higher x. Infrared (IR) results revealed that the glassy matrix are composed of TeO₃, TeO₃₊₁, TeO_4, BiO₆ and NbO₆ structural units. The changes in the density (ρ), molar volume (V_m), oxygen molar volume (V₀) and oxygen packing fraction (OPD) have correlated with structural changes in the glass network. The optical studies show an absorption bands below the absorption edge in the glass samples.     

Optical and acoustic properties of TeO2/WO3 glasses with small amount of additive ZrO2

The optical and acoustic properties of tellurite glasses in the system TeO₂/ZrO₂/WO₃ have been investigated. The refractive index at different wavelengths and the optical spectra of the glasses have been measured. From the refractive index and absorption edge studies for prepared glasses, the optical parameter viz; optical band gap (E_opt), Urbach energy, (ΔE), dispersion energy, E_d, and the average oscillator energy, E₀, have been calculated. Sound velocities were measured by pulse echo technique. From these velocities and densities values, various elastic moduli were calculated. The variations in the refractive index, optical energy gap and elastic moduli with WO₃ content have been discussed in terms of the glass structure. Quantitatively, we used the bond compression model for analyzing the room temperature elastic moduli data. By calculating the number of bonds per unit volume, the average stretching force constant, and the average ring size we can extract valuable information about the structure of the present glasses.     

Spectroscopic study of ZnO doped CeO2-PbO-B2O3 glasses

Glass samples of compositions xZnO-xCeO₂-(30−x)PbO-(70−x)B₂O₃ with x varying from 2% to 10% mole fraction are prepared by the melt quench technique. The structural and optical analysis of glasses is carried out by XRD, FTIR, density and UV-visible spectroscopic measurement techniques. The FTIR spectral analysis indicates that with the addition of ZnO contents in glass network, structural units of BO₃ are transformed into BO₄. It has been observed in our previous work that band gap decreases from 2.89 to 2.30 eV for CeO₂-PbO-B₂O₃ glasses with cerium content varying from 0% to 10% [Gurinder Pal Singh, Davinder Paul Singh, Physica B 406(3) (2011) 640-644]. With the incorporation of zinc in CeO₂-PbO-B₂O₃ glasses, the optical band gap energy decreases further from 2.38 to 2.03 eV. This causes more compaction of the borate network, which results in an increase of density (3.39-4.02 g/cm³). Transmittance shows that ZnO in glass samples acts as a reducing agent thathelps to convert Ce⁴⁺→Ce³⁺ ions.     

Structural and optical properties of lithium borobismuthate glasses

Glasses with compositions 25Li₂O-(75−x)Bi₂O₃-x B₂O₃, with 0?x?30 mol%, have been prepared using the melt quenching technique. The density and the molar volume have been determined. IR spectroscopy is used as a structural probe of the nearest neighbor environment in the glass network. 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_g^opt for indirect transition and refractive index have been determined for 0?x?30 mol%. The average electronic polarizability of the oxide ion α_o²⁻ and the optical basicity have been estimated from the calculated values of the refractive indices. Variations in the different physical parameters such as the density, molar volume, optical band gap, refractive index, average electronic polarizability of the oxide ion and optical basicity with B₂O₃ content have been analyzed and discussed in terms of the changes in the glass structure.     

Spectral studies of Erbium doped heavy metal borophosphate glass systems

The ternary lead bismuth magnesium borophosphate glass system (LBMBPE) with molar concentrations of (50-x) PbO-xBi₂O₃-25MgHPO₄-24B₂O₃-1Er₂O₃ (x=10, 20, 30 and 40) was prepared using Melt quenching technique. The amorphous nature of these glass samples were confirmed with XRD studies, The spectral data from the optical absorption studies was employed to compute the spectroscopic parameters such as Racah coefficients (E¹, E² and E³), spin-orbit coupling (ξ_4f), configuration interaction factor (α) and Judd-Ofelt intensity parameters (Ω_λ, λ=2, 4 and 6). The IR spectra exhibit the presence of vibrational modes of phosphates, borate radicals, bismuth, lead and magnesium ions. The Judd-Ofelt parameterization indicates the covalency and vibrationonic frequencies of the ligands with rare earth ions. The radiative parameters such as radiative transition probabilities (A), the total radiative transitional probabilities (A_T), radiative life times (τ_R), branching ratios (β) and absorption cross sections (∑) were computed for certain lasing levels. The effect of compositional changes on the optical band gap is also reported. The glass systems thus developed indicate their potential lasing candidature.     

Structural and spectroscopic studies on concentration dependent Er3+ doped boro-tellurite glasses

Er³⁺ doped boro-tellurite glasses have been prepared by the conventional melt quenching technique with the chemical composition (39?x) B₂O₃+30TeO₂+15MgO+15K₂O+xEr₂O₃ (where x=0.01, 0.1, 1, 2 and 3 wt%). The structural analysis of the glasses were made through XRD, FTIR spectral measurements and the optical absorption, luminescence measurements were made to analyze the optical behavior of the prepared glasses. The bonding parameters were determined from the optical absorption spectra and were found to be ionic in nature. The experimental oscillator strengths were determined from the absorption spectra have been used to determine the Judd–Ofelt parameters. The Judd?Ofelt parameters were used to explore the important radiative parameters such as transition probability (A), stimulated emission cross-section (σ_P^E) and branching ratios (β_R) of the emission transitions ²H_9/2→⁴I_15/2 and ²H_11/2 and ⁴S_3/2→⁴I_15/2 of the trivalent erbium ions. The optical band gap energy (E_opt) values corresponding to the direct and indirect allowed transitions and the Urbach energy values of the prepared Er³⁺ doped boro-tellurite glasses have been calculated and discussed with similar studies. The spectroscopic behavior of the Er³⁺ boro-tellurite glasses have been studied by varying the trivalent erbium ion content and the results were discussed and compared with similar studies.     

Mixed alkali effect in boroarsenate glasses

We report, for the first time the study of mixed alkali effect (MAE) in boroarsenate glasses. Density, DSC, DC electrical conductivity and IR studies have been carried out for xK₂O-(40−x)Na₂O-50B₂O₃-10As₂O₃ glasses. The DC electrical conductivity was measured in the temperature range 100 °C to below the glass transition temperature. The strength of the MAE in T_g, DC electrical conductivity and activation energy has been determined. It is observed that the strength of MAE in DC electrical conductivity is less pronounced with increase in temperature. The results are explained by the structural model recently proposed by Swenson and coworkers, supporting molecular dynamic results. The IR studies show that the glass system contains BO₃ and BO₄ units in the disordered manner.     

Optical and other spectroscopic studies of lead, zinc bismuth borate glasses doped with CuO

10MO·20Bi₂O₃·(70−x)B₂O₃·xCuO [M=Pb, Zn] with x=0, 0.4 and 0.8 (wt%) glasses were synthesized by the melt-quenching technique and were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Physical parameters, like density, and spectroscopic studies (optical absorption, EPR, FTIR and photoluminescence) were used to understand the role of modifier oxide and CuO in the glass matrix. A red shift of the absorption band corresponds to ²B_1g→²B_2g transition of Cu²⁺ ions from P2 to Z4 samples and the increase of hyperfine splitting factor (A_‖) from P2 to Z2 shows that with the integration of PbO by ZnO the electron density around copper ion is increased. It is also supported by the gradual increase in theoretical optical basicity values of ZnO mixed glasses, as compared to that of PbO mixed glass matrix. Reduced bismuth radicals are found in undoped and 0.4% CuO doped glasses of both the series. Analysis of the absorption and emission studies indicates that the concentration of luminescence centers of bismuth ions (Bi³⁺ ions in UV region) is decreased by the integration of ZnO as well as by increasing the dopant concentration. In lead series PbO₄ and BiO₃ units are increased from P2 to P4 and in zinc series BiO₃ units are decreased from Z0 to Z4. The conductivity of the glass matrices is increased in both the series with the dopant of CuO.     

Effect of CuO addition on the optical and electrical properties of sodium zinc borophosphate glasses

Sodium borophosphate glasses doped with copper ions having general composition 20Na₂O-20ZnO-25B₂O₃-(35-x) P₂O₅-x CuO (x=1-8 mol %) were prepared using conventional melt-quench method and characterized by density, UV-visible optical absorption, photoluminescence and conductivity measurements. E_optical values for different glass samples are found to decrease systematically from 3.5 to 2.5 eV with increase in CuO content in the glass. Network modifying action of CuO with the glass network has been confirmed from the UV-visible optical absorption studies. Presence of Copper in the form of Cu⁺ species has been confirmed from photoluminescence measurements. The electrical conductivity (σ) increases with increase in copper oxide content in the glass and temperature dependence of electrical conductivity confirmed the semiconducting nature of the samples.     

Spectroscopic studies of tantalum doped borate glasses

Glasses with formula 30Li₂O 60B₂O₃xTa₂O₅ (10−x) Bi₂O₃ for x=0, 2, 4, 6 and 8 were prepared via normal melt quenching technique and characterized by refractive index and MDSC. Refractive index (μ) and glass transition temperature (T_g) are found to increase with increase in dopant concentration. Impedance spectra of the samples were recorded in the frequency range 100 Hz–5 MHz in the temperature range 175–275 °C. The plots are typical of those recorded for disordered systems. Conductivities and relaxation times are found to follow Arrhenius type of relation and activation energies are calculated. Optical absorption spectra were recorded in the wavelength range 200–900 nm range from which cutoff wavelength (λ_c) and optical band gap energy (E_g) are evaluated. λ_c is found to decrease while E_g to increase with increase in composition. FTIR spectra of the samples were recorded in the frequency range 400–1500 cm⁻¹ which exhibit characteristic bands corresponding to BO₃, BO₄ stretching vibrations and BO bending vibration. Tightening of the structure is indicated by increase in the vibration of BO₃ at the cost of BO₄ for 8 mol% of Ta₂O₅. This is in support of the highest value of T_g for this sample among the series. Raman spectra of the samples were recorded in the frequency range 200–1200 cm⁻¹. With successive addition of Ta₂O₅, increase in the vibration of Ta–O groups TaO₆ groups to be responsible for observed increase in μ and T_g. An attempt is made to prepare tantalum doped borate glasses and study them by spectroscopic techniques.     

Spectroscopic analysis and magnetic susceptibility of CuO-TeO2-V2O5 glasses

This article reports on the structure of the glassy system xCuO-65TeO₂-(35−x)V₂O₅, 5≤x≤10 mol% which was studied using infrared (IR) and Raman spectroscopy methods as well as magnetic susceptibility measurements. IR and Raman spectroscopy analysis reveals the presence of four main absorption bands attributed to [TeO₃], [TeO₄], [VO₄], and [VO₅] structure units. It suggests that Cu²⁺ ions occupy the available open spaces of the Te-O network without straining the bonds too much. Increasing the concentration of Cu²⁺ ions beyond 5 mol% results in the modification of the glass by straining and locally distorting the surrounding of the Te-O network. The magnetic susceptibility of these materials was investigated in the temperature range of 5-200 K revealing the paramagnetic behavior described by the Curie-Weiss law and indicating the presence of weak antiferromagnetic exchange interactions between Cu ions. The magnetic entropy change of the glasses was determined based on the temperature and magnetic field dependence of magnetization.     

Theoretical and experimental IR spectra of binary rare earth tellurite glasses—1

The binary rare earth tellurite glasses (A_nO_m)_x-(TeO₂)_1−x, where x = 0.1 and A = Sm, Ce, La, were prepared by melting the oxides at 800°C for 1 h and quenched rapidly. The IR spectra has been measured in the frequency region 4000-200 cm⁻¹. The main absorption bands in these glasses related to the characteristics of TeO₂. The detected shift in these bands are found to be sensitive to the glass structure. The A-O bond vibration in the glasses has been calculated. The results were interpreted on the basis of stretching force constant of each bond.     

Electrical and optical properties of GexFexSe100−2x chalcogenide thin films

Optical absorption at room temperature and electrical conductivity at temperatures between 283 and 333 K of vacuum evaporated Ge_xFe_xSe_100−2x (0≤x≤15) amorphous thin films have been studied as a function of composition and film thickness. It was found that the optical absorption is due to indirect transition and the energy gap increases with increasing both Ge and Fe content; on the other hand, the width of the band tail exhibits the opposite behavior. The optical band gap E_opt was found to be almost thickness independent. The electrical conductivity show two types of conduction, at higher temperature the conduction is due to extended states, while the conduction at low temperature is due to variable range hopping in the localized states near Fermi level. Increasing Ge and Fe contents were found to decrease the localized state density N(E_F), electrical conductivity and increase the activation energy for conduction, which is nearly thickness independent. Variation of the atomic densities ρ, molar volume V, glass transition temperature T_g cohesive energy C.E and number of constraints N_Co with average coordination number Z was investigated. The relationship between the optical gap and chemical composition is discussed in terms of the cohesive energy C.E, average heat of atomization and coordination numbers.     

Enhanced spectroscopic properties and Judd–Ofelt parameters of Er-doped tellurite glass: Effect of gold nanoparticles

Glasses with composition 70TeO₂–20ZnO–10Na₂O–0.5Er₂O₃–(x)Au are synthesized by melt-quenching technique. Their spectroscopic and optical characterizations are made. The presence of gold nanoparticles (Au NPs) with average size ～9 nm is confirmed from TEM micrograph. The value of E_dir is found to lie between 3.082 and 3.073 eV, while E_indir lies within 2.765 to 2.724 eV. The observed visible up-conversion (UC) emission under 779 nm excitation wavelength exhibits two bands centered at 546 nm (green) and 637 nm (red) in all samples. The glass with 0.4 mol% Au NPs shows dominant enhancement in the UC emission intensity of the order of 3.5 times for the green band (⁴S_3/2 → ⁴I_15/2) and a weaker enhancement for the red (⁴F_9/2 → ⁴I_15/2) band. The optical properties of the system are affirmed to depend strongly on the Au concentration in the dielectric medium. The absorption spectra consist of six bands attributed to absorption from ground state (⁴I_15/2) to ⁴I_13/2, ⁴I_11/2, ⁴I_9/2, ⁴F_9/2, ²H_11/2, and ⁴F_7/2 excited states. The structural reveals that the types of bonding and difference in electro-negativity can be manipulated by the presence of metallic NPs in glass matrix. Judd–Ofelt analysis asserts the increase in Ω₂ and Ω₆ parameters with the addition of Au NPs and the enhancement of green and red emissions. The enhancement is mainly attributed to large plasmonic effect of Au NPs. The proposed glasses can be nominated as potential materials for solid state laser developments.     

Effect of B2O3 on the structure and properties of tungsten–tellurite glasses

The elastic properties and Debye temperatures of xB₂O₃–70TeO₂–(30–x)WO₃, (0 ≤ x ≤ 30 mol%) glasses have been investigated using sound velocity measurements at 4 MHz. Ultrasonic and thermal parameters, combined with the results of IR spectroscopic analyses, were employed to explore the effect of B₂O₃ on the structure of tungsten–tellurite glasses. According to IR analysis, there is competition between WO₆ and TeO₄ units to form BO₄ units, and the vibrations of the tellurite structural units are shifted towards lower wavenumbers on the formation of non-bridging oxygens. It is assumed that B₂O₃ acts as a modifier by decreasing the glass-transition temperature T _g and increasing both the thermal stability and glass formation range of the tellurite glasses. The change in density and molar volume with B₂O₃ content reveals that the borate units are less dense than the tellurite structural units. The observed compositional dependence of elastic moduli is interpreted in terms of the effect of B₂O₃ on the coordination number of the tellurite units. A good correlation was observed between experimentally determined elastic moduli and those computed with the Makishima–Mackenzie model.     

Optical absorption spectrum of Cu2O-CaO-P2O5 glasses

Homogeneous CaO-P₂O₅ and Cu₂O-CaO-P₂O₅ glasses were prepared using a melt-quenched method under controlled conditions. The binary glasses were found to be colourless and transparent while the ternary glasses changed from light green to dark green as the Cu₂O content increased. From the absorption edge studies, the values of the optical band gap, E_opt and Urbach energy, ΔE were evaluated. The position of the absorption edge and hence the optical band gap were found to depend on the glass composition. Analysis of the optical band gap shows that for the binary glasses, the value increases as the content of CaO decreases, while for the ternary glasses, the value of the optical band gap increases as the content of the Cu₂O decreases. The density of the glasses was also measured and was found to increase with the increase in CaO and Cu₂O contents.