Thermal and spectroscopic properties of Tm3 + doped TZPPN transparent glass laser material

In this work a transparent bulk glass with the mol% composition 76TeO₂·10ZnO·9.0PbO·1.0PbF₂·3.0Na₂O doped with Tm^3 + has been synthesized. Results of differential thermal analysis (DTA) indicate a high thermal stability and low tendency to crystallization of this glass. The refractive indices at different wavelengths, the Urbach energy, the optical energy gap, the Sellmeier gap energy and the dispersion energy have been estimated. Spectroscopic quality factor of Tm^3 + was evaluated from optical absorption spectra. Electric and magnetic dipole transition probabilities, branching ratios, and radiative lifetimes of several excited states of Tm^3 + have been predicted using calculated intensity Judd–Ofelt parameters. The classical McCumber theory has been applied to evaluate the emission cross-sections for ³F₄ → ³H₆ transition around 1.8 μm. This study shows that TZPPN glass doped with Tm^3 + ions is a promising candidate for laser applications.     

Bond character,optical properties and ionic conductivity of Li2O/B2O3/SiO2/Al2O3 glass: Effect of structural substitution of Li2O for LiCl

A glass of composition (20 ? x)Li₂O–xLiCl–65B₂O₃–10SiO₂–5Al₂O₃ where 0 ? x ? 12.5 wt% is prepared using the normal melt-quenching technique. The optical constants and electrical conductivity and their correlation are investigated, furnished and discussed with the substitution of Li₂O for LiCl. The mechanism of the optical absorption and the calculated Urbach energy follow the rule of phonon-assisted transitions. The ionic conduction mechanism is determined by activation energy process. Substitution up to 10 wt% LiCl provides high ionic conductivity (1.9 × 10^?2 Ω^?1 m^?1) due to the high average electronegativity of LiCl which increases the polarizability of lithium ions. The small cation–anion distance approach confirmed the enhancement in ionic conductivity of LiCl containing glass compared to that of Li₂O. Due to the large size of Cl^? ions, there is an expansion of the lattice which in turn broadens the available path windows. For 12.5 wt% LiCl, anomalous density behavior is observed and a reduction in conductivity is occurred, σ = 5.4 × 10^?3 Ω^?1 m^?1. Owing to the model of bond fluctuation, the reduction is attributed to the increase in the alkali halide concentration which creates bottlenecks that hinder the motion of Li⁺ ions. The ionic conductivity character is strongly supported by the behavior of the glass ionicity factor, density, molar volume, refractive index, average boron–boron separation, molar refraction, metallization criterion and non-bridging oxygen concentration of the studied glass.     

The effect of fluoride on the Fe2+/Fe3+-redox equilibrium in glass melts in the system Na2O/NaF/CaO/Al2O3/SiO2

Liquids with the base compositions (16 − x/2)Na₂O · xNaF · 10CaO · 74SiO₂ (x = 0, 1, 3, and 4) and (10 − x/2) · Na₂O · xNaF · 10CaO · yAl₂O₃ · (80 − y)SiO₂ (x = 0, 1, 3, 5 and y = 5 and 15) doped with 0.25 mol% Fe₂O₃ were studied by means of square-wave voltammetry in the temperature range from 1000 to 1500 °C. With increasing temperature, the redox equilibria were shifted to the reduced state. Also while increasing the alumina concentration, the Fe²⁺/Fe³⁺-redox equilibrium is shifted to the reduced state. In the soda-lime–silica melt the addition of fluoride shifts the equilibrium to the oxidized state, while in the aluminosilicate melts with 15 mol% Al₂O₃, the equilibrium is shifted to the reduced state. In the aluminosilicate melts with 5 mol% Al₂O₃, the equilibrium was not affected by the fluoride concentration. This is explained by the structure of the respective glass compositions.     

Electric field induced structural modification and second order optical nonlinearity in potassium niobium silicate glass

Second harmonic generation properties have been studied in 23 K₂O · 27Nb₂O₅ · 50 SiO₂ glass subjected to thermal poling. The poling-induced optical nonlinearity, with χ⁽²⁾ = 3.8 pm/V, has been related to structural modifications within a surface layer of a few microns on the anode side, as evidenced by means of confocal micro-Raman mapping along the sample thickness. The data indicate that the structural changes result from a charge transport process that causes network modifications in an alkali depleted layer whose thickness is comparable with that of the non-linear region. The Raman data also indicate that in the alkali depleted layer the network polymerization degree increases as a consequence of ion migration. The origin of the nonlinearity and the mechanisms activated by poling are discussed. The mechanism of non-bridging-oxygen to bridging-oxygen bond switching is proposed to explain ion migration and the subsequent structural changes in the glass.     

Growth and characterization of nanostructured CdS/Polyaniline/CuInSe2 thin films for solar cell applications

In the present paper, we report about synthesis of nanostructured organic–inorganic heterojunction of CdS/Polyaniline/CuInSe₂ thin films by cost effective chemical route at room temperature, for solar cell application. As such obtained thin films are characterized for structural, compositional, morphological, optical and electrical properties by X-ray diffraction (XRD) pattern, energy dispersive X-ray (EDAX) analysis, scanning electron microscopy (SEM), optical absorbance spectra and I–V response respectively. The XRD reveals the polycrystalline nature of the thin films having tetragonal crystal structure and a crystallite size of 19 nm. The presence of observed and expected elements in the EDAX spectra confirms the elemental compositions in CdS/Polyaniline/CuInSe₂ thin films. From SEM images it can be inferred that the surface morphology of the Polyaniline thin films exists like clothing fibers, while CdS/CuInSe₂ shows granular shape particles distributed over the substrate and the SEM of CdS/Polyaniline/CuInSe₂ represents mixing and attachment of circular particles to fiber like structure. The optical absorbance spectra have shown red shift in absorbance strength and energy band gap value of CdS/CuInSe₂ from ~ 1.36 eV to ~ 1.62 eV upon formation of CdS/Polyaniline/CuInSe₂ thin film. The I–V response of CdS/CuInSe₂ and CdS/Polyaniline/CuInSe₂ measured under dark and illumination to 100 mW/cm² light, exhibited the solar characteristics from these graphs and the conversion efficiency calculated is observed to be 0.26 and 0.55% for CdS/CuInSe₂ and CdS/Polyaniline/CuInSe₂ thin films respectively.     

Temperature dependent blue second harmonic generation in Ba5Li2Ti2Nb8O30 microcrystals embedded in TeO2 glass–matrix

The as-quenched samples in the system (100 ? x) TeO₂-(x) Ba₅Li₂Ti₂Nb₈O₃₀ (2 ? x ? 8) were found to be embedded with 10–20 μm sized crystallites of the polar phase Ba₅Li₂Ti₂Nb₈O₃₀ (BLTN). Blue (400 nm) second harmonic generation (SHG) was observed in transmission mode when 800 nm laser light was allowed to pass through the individual crystallites. The blue SHG signal was temperature dependent and its intensity was maximum at ～175 °C which was tentatively attributed to the concomitant changes associated with the refractive indices of the BLTN crystallites. The SHG intensity attained a minimum value around the Curie temperature of BLTN crystals.     

Electrooptical Kerr phenomenon and Raman spectroscopy of one lithium–niobium–silicate glass-forming system

Raman spectra and electrooptical Kerr coefficients of glasses belonging to one lithium–niobate–silicate glass-forming system xNb₂O₅ · (66 ? x)SiO₂ · 19Li₂O · 11K₂O · 2B₂O₃ · 2CdO are studied. It has been found that these glasses demonstrate a record value of electrooptical Kerr coefficient; the glass with x = 35 showed electrooptical Kerr coefficient equal to 266 × 10^?16 m/V². Using Raman spectroscopy combined with the concept of Constant Stoichiometric Groupings, a correlation of electrooptical Kerr coefficients of these glasses with the content of Li₂O · Nb₂O₅ (or 2LiNbO₃) groupings has been demonstrated. The hypothesis that electrooptical Kerr sensitivity of glasses is related to the ordered regions with composition and symmetry corresponding to some of known electrooptical crystals has been verified. These regions, which the authors called ‘Crystal Motifs’, are identified with the groupings found in studying Raman spectra of the glasses.     

Structure and properties of NaPO3–ZnO–Nb2O5–Al2O3 glasses

In an effort to design low-melting, durable, transparent glasses, two series of glasses have been prepared in the NaPO₃–ZnO–Nb₂O₅–Al₂O₃ system with ZnO/Nb₂O₅ ratio of 2 and 1. The addition of ZnO and Nb₂O₅ to the sodium aluminophosphate matrix yields a linear increase of properties such as glass transition temperature, density, refractive index and elastic moduli. The chemical durability is also significantly, but nonlinearly, improved. The glass with the highest niobium concentration, 55NaPO₃–20ZnO–20Nb₂O₅–5Al₂O₃ was found to have a dissolution rate of 4.5 × 10^? 8 g cm^? 2 min^? 1, comparable to window glass. Structural models of the glasses were developed using Raman spectroscopy and nuclear magnetic resonance spectroscopy, and the models were correlated with the compositional dependence of the properties.     

IR absorption spectra of lithium and silver vanadium–tellurite based glasses

The aim of the present paper is to give structural information in order to set a correlation between the electrical conductivity behavior and structures of lithium and silver vanadium–tellurite based glasses. We report our structural studies and compare the effect of the nature of the metallic cation on glasses of the form XM₂O · (1 − X)V₂O₅ · 2TeO₂ (where 0 ⩽ X < 1 and M = Li or Ag). Fourier transform infra-red (FTIR) spectra were recorded for all compositions and complementary differential scanning calorimetry (DSC) measurements and X-ray diffraction (XRD) measurements were also carried out. This paper should be considered as complementary to a previous article reporting the conductive behavior of theses glasses. In the latter we reported the obtained results on electrical conductivity studies. The results confirm the existence of a transition from a typically electronic (polaronic) conductive regimen when the molar fraction (X) of M₂O is equal to 0, to an ionic conductive regimen when X tends to 1. The evidence for the independent migration path for both electrons and ions was put into evidence by studying the electrical conductivity behavior in a complementary system of the form X M₂O · (1 − X)[0.5V₂O₅–0.5MoO₃] · 2TeO₂. In this system vanadium was partially replaced by molybdenum which acts as a ‘diluting’ agent of the active centers involved in the electronic transport.     

The effect of RO (R = Mg,Ca, Ba and Zn) on physical properties of Na2O/Al2O3/B2O3/SiO2 glasses for the preparation of gradient index micro lenses

Glasses in the system Na₂O–Al₂O₃–B₂O₃–SiO₂ doped with MgO, CaO, BaO or ZnO (concentrations: 2.5%–5 mol%) were melted from the raw materials and studied with respect to their densities, hydrolytic durabilities, crystal growth velocities, specific ionic conductivities, refractive indices, Abbe numbers and optical transmissions. The samples were ion exchanged in a NaNO₃/AgNO₃ salt melt in order to determine the Na⁺/Ag⁺ interdiffusion coefficients and the refractive indices, Abbe numbers and optical transmissions of the ion exchanged silver containing glasses. Glasses doped with ZnO are advantageous for the production of gradient index lenses due to their improved chemical durability and smaller crystal growth velocities at viscosities in the range of 10⁵–10⁶ dPa s. The optical properties of these glasses are similar to those of glasses without RO.     

Mixed transition-ion effect in the glass system: Fe2O3-MnO-TeO2

In earlier studies on phosphate and tellurite glasses containing vanadium and iron oxides, non-linear variation of physical properties as functions of the ratios of the transition ions (V/V + Fe) were observed. The most striking effect was observed with electrical conductivity, where a 3 orders of magnitude reduction in conductivity was observed at a V/V + Fe ratio of ~ 0.4. The effect was termed Mixed Transition-ion Effect or MTE. In phosphate glasses, however, MTE was not observed when one of the transition ions was manganese. It was concluded that Mn does not contribute to conduction in these glasses. In the present study, we demonstrate a mixed transition ion effect in tellurite glasses containing MnO and Fe₂O₃ (xFe₂O₃(0.2 ? x) MnO0.8TeO₂ with x varying from 0 to 0.2). A maximum in the property at an intermediate composition (x = 8.5 mol%), was observed in DC resistivity, activation energy, molar volume etc. Mossbauer and optical absorption (UV–VIS–NIR) measurements were performed on these glasses and the transport mechanism has been identified to be hopping of small polarons between Fe^3 + (Mn^3 +) and Fe^2 + (Mn^2 +) sites.     

Kerr studies of several tellurite glasses

Estimates of Kerr electrooptical sensitivity of several tellurite glasses are presented. The highest value of Kerr coefficient B ～ 190 × 10^?16 m V^?2 is registered for 0.6TeO₂–0.3TlO_0.5–0.1ZnO glass. This evidences the prospects of thallium–tellurite glass system for electrooptical applications. A gradual decrease of B from 41 × 10^?16 to 26 × 10^?16 m V^?2 in (1 ? x) TeO₂ – xNbO_2.5 system is revealed for x increasing from 0.1 to 0.15. No crystalline phase was found in that system, thus allowing attributing its Kerr sensitivity to the intrinsic properties of the glass matrix. The Kerr coefficient variation from 66 to 81 × 10^?16 m V^?2 was observed for 0.85TeO₂–0.15WO₃ glasses co-doped with small amounts of silver and cerium. The analysis of optical absorption spectra of several silver-containing tellurium–tungsten oxide glasses makes it possible to think that introducing cerium provokes formation of new mid-range orderings.     

Square-wave voltammetry and impedance spectroscopy in iron-doped melts of the system Li2O/Al2O3/SiO2

Glass melts with the basic compositions xLi₂O · 15Al₂O₃ · (85 − x)SiO₂ (x = 8.5, 11, 13.5, 16 and 18.5) doped with 0.25 mol% Fe₂O₃ were studied by square-wave voltammetry and impedance spectroscopy at temperatures in the range from 1100 to 1600 °C. The square-wave voltammograms show a pronounced peak attributed to the reduction of Fe³⁺ to Fe²⁺. The attributed peak potentials which are equal to the standard potentials of the redox pair decrease linearly with the temperature. Impedance spectra measured could be simulated using an equivalent circuit attributed to a simple electron transfer reaction controlled by diffusion.     

Evolution of nanocrystalline BaBi2Nb2O9 in Li2B4O7–BaO–Bi2O3–Nb2O5 glass system

Transparent glasses and glass nano crystal composites (GNCs) of various compositions in the system (100 − x)Li₂B₄O₇–x(BaO–Bi₂O₃–Nb₂O₅) (where x = 10, 20, and 30 in molar ratio) were fabricated via splat-quenching technique. The glassy nature of the as-quenched samples was established by differential thermal analyses. X-ray powder diffraction and transmission electron microscopic (TEM) studies confirmed the formation of layered perovskite BBN via a fluorite like phase. TEM studies revealed the presence of 10 nm sized spherical crystallites of fluorite like BaBi₂Nb₂O₉ phase in the glassy matrix of Li₂B₄O₇ (LBO). The influence of composition on the dielectric and the optical properties (transmission, optical band gap) of these samples has been investigated.     

Thermo-optical properties and nonradiative quantum efficiency of Er3+-doped and Er3+/Tm3+-co-doped tellurite glasses

Thermal lens (TL) measurements were performed in tellurite glasses, 70TeO₂–19WO₃–7Na₂O–4Nb₂O₅ (mol%), undoped, doped with Er³⁺ (1.19 × 10²⁰ ions/cm³) and co-doped with Er³⁺ (1.19 × 10²⁰ ions/cm³)/Tm³⁺ (1.56 × 10²⁰ ions/cm³). The absolute nonradiative quantum efficiency (ϕ) was determined by the TL method. The ϕ values for Er³⁺/Tm³⁺-co-doped and Er³⁺-doped tellurite glasses were 0.98 and 0.74, respectively. Fluorescence spectra were performed at λ_e = 488 nm and used to estimate the fluorescence quantum efficiency (η) using the TL results. These values were compared with results obtained by Judd–Ofelt calculations.     

Characterization of B2O3 and/or WO3 containing tellurite glasses

Characterization of B₂O₃ and/or WO₃ containing tellurite glasses was realized in the 0.80TeO₂–(0.20 ? x)WO₃ ? xB₂O₃ system (0 ≤ x ≤ 0.20 in molar ratio) by using differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectrometry techniques. Glasses were prepared with a conventional melt-quenching technique at 750 °C. To recognize the thermal behavior of the glasses, glass transition and crystallization temperatures, glass stability value, glass transition activation energy, fragility parameter were calculated from the thermal analyses. Density, molar volume, oxygen molar volume and oxygen packing density values were determined to investigate the physical properties of glasses. Fourier transform infrared spectra were interpreted in terms of the structural transformations on the glass network, according to the changing B₂O₃ and/or WO₃ content. Crystallization behavior of the glasses was investigated by in situ X-ray diffraction measurements and microstructural characterization was realized by scanning electron microscopy and energy dispersive X-ray spectrometry analyses.     

FTIR and UV–VIS spectroscopy investigations on the structure of the europium–lead–tellurate glasses

Glasses in the xEu₂O₃·(100-x)[4TeO₂·PbO₂] system where 0 ≤ x ≤ 50 mol% have been prepared using the melt quenching method. The influence of europium ions on the structure of lead–tellurate glasses has been investigated using density measurements, FTIR and UV–VIS spectroscopy. Structural changes produced by increasing the rare earth concentration were followed.The europium and lead ions show a preference towards [TeO₃] structural units causing a deformation of the TeOTe linkages. Structural changes inferred by analyzing the band shapes of IR spectra revealed that the increase of the Eu^+ 3 content causes the intercalation of [EuO_n] entities in the [TeO₄] chain network. The excess of oxygen can be supported into the glass network by the formation of [PbO_n] and [EuO_n] structural units.The UV–VIS spectroscopy data show that europium ions enter the glass matrix in the Eu²⁺ and Eu³⁺ valence states, the last being predominant in the studied glasses. The Pb^+ 2 ions produce strong absorption in the ultraviolet domain.     

Crystallization of a niobium phosphate glass

Niobium phosphate glasses with composition 37P₂O₅ · 23K₂O · 40Nb₂O₅ are stable in relation to crystallization during the heating process, exhibit a low critical cooling rate, and are potentially good for nuclear wasteforms. The crystallization of these glasses was evaluated by optical microscopy after proper heat treatments, showing that surface crystallization is the main process occurring during the heat treatment. Two main crystalline phases were observed. These crystalline phases were KNb₃O₈ and K₃NbP₂O₉. Surface crystal growth rates were measured in the temperature range of 806–972 °C (T_g = 683 °C) for both crystalline phases. Apparent crystallization enthalpies were determined through the Arrhenius plots of lnU vs. 1/T. The enthalpies are 496 kJ/mol and 513 kJ/mol for each crystalline phase, respectively. The surface density of nucleation sites (N_s) on 3 μm diamond paste polished surfaces is (2.4 ± 0.7) × 10⁸ nuclei/m² for one crystalline phase and (9.8 ± 0.8) × 10⁹ nuclei/m² for the other crystalline phase, when revealed at 838 °C/17.5 h, and these values show a slight variation depending on the time and the temperature. At the tested temperatures, only one crystal phase appeared inside the volume, and a volume density of nucleation sites N_v = 5 × 10⁶ nuclei/m³ was measured.     

Spectroscopic properties of Tm3+ doped TeO2-R2O-La2O3 glasses for 1.47 μm optical amplifiers

Upon excitation at 808 nm laser diode, an intense 1.47 μm infrared fluorescence has been observed with a broad full width at half maximum (FWHM) of about 124 nm for the Tm³⁺-doped TeO₂-K₂O-La₂O₃ glass. The Judd–Ofelt parameters found for this glass are: Ω₂ = 5.26 × 10^?20 cm², Ω₄ = 1.57 × 10^?20 cm² and Ω₆ = 1.44 × 10^?20 cm². The calculated emission cross-sections of the 1.47 μm transition are 3.57 × 10^?21 cm², respectively. It is noted that the gain bandwidth, σ_e × FWHM, of the glass is about 440 × 10^?28 cm³, which is significantly higher than that in ZBLAN and Gallate glasses, a high gain of 35.5 dB at 1470 nm can be obtained in a TKL glass fiber. TeO₂-R₂O (R = Li, Na, K)-La₂O₃ glasses has been considered to be more useful as a host for broadband optical fiber amplifier.     

Evaluation of chemical durability,thermal properties and structure characteristics of Nb–Sr-phosphate glasses by Raman and NMR spectroscopy

Thermal properties, water durability and structure of Nb₂O₅–SrO–P₂O₅ glasses containing 0–25 mol% Nb₂O₅ and 35–60 mol% SrO were explored aiming to develop high refractive index optical glasses. Structure studied using Raman and NMR spectra reveals that by increasing Nb₂O₅ content, niobium plays the role as intermediate. Nb⁵⁺ tends to break P–O–P and O–P–O bonds forming [NbO₆] structure. Thus fractions of Q³ and Q² decrease, while Q¹ fraction increases. Furthermore the Q⁰ fraction replaces the lessened Q³ fraction. As P₂O₅ content is reduced to 30 mol%, partial [NbO₆]_octa turns into [NbO₄]_tetra and partial (Nb–O)_short-octa becomes (Nb–O)_short-tetra bond to stabilize the glass structure. Glass-transition and softening-temperatures of the glasses increase by increasing SrO and Nb₂O₅ contents. Thermal expansion coefficient increases by increasing SrO while decreases with Nb₂O₅ content. Water durability is enhanced as increasing Nb₂O₅ and SrO contents. Properties of the glasses correlate well with the worked out structure.