Infrared spectra of zinc doped lead borate glasses

The infrared spectra of zinc-doped lead borate glasses (10–30 mol% ZnO) were measured over a continuous spectral range (400–4000 cm⁻¹) in an attempt to study their structure systematically. No boroxol ring formation was observed in the structure of these glasses. The formation of Zn in tetrahedral coordination was not observed. The conversion of three-fold to four-fold coordinated boron took place.     

Dielectric properties of NaF-B2O3 glasses doped with certain transition metal ions

Dielectric constant ε, loss tan δ, a.c. conductivity Σ and dielectric breakdown strength of NaF-B₂O₃ glasses doped with certain transition metal ions (viz. Cu²⁺, VO²⁺, Ti⁴⁺ and Mn⁴⁺) are studied in the frequency range 10²-10⁷ Hz and in the temperature range 30–250°C. The values of ε, tan δ, Σ_a.c. are found to be the highest for Cu²⁺ doped glasses and the lowest for Mn⁴⁺ doped glasses. Activation energy for a.c. conduction and the value of dielectric breakdown strength are found to be the lowest for Cu²⁺ doped glasses and the highest for Mn⁴⁺ doped glasses. With the help of infrared spectra, increase in the values of ε and tan δ of these glasses with frequency and temperature are identified with space charge polarization. An attempt has been made to explain a.c. conduction phenomenon on the basis of quantum mechanical tunneling model (QMT)/carrier barrier hopping model.     

Effect of CdS nanoparticles on photoluminescence spectra of Tb<Superscript>3 + </Superscript> in sol–gel-derived silica glasses

CdS nanoparticles doped with Tb^3 + were synthesized by sol–gel technique. The influence of CdS on the Tb^3 + glass was studied by UV-Visible and luminescence spectroscopy. The luminescence intensity of the glasses increased significantly in the presence of CdS nanoparticles. Terbium ions excited into the ⁵ D ₃ level have a rich emission spectrum in the 400–700 nm range decaying to different ⁷ F _J levels. The intensity of violet and blue luminescence from ⁵ D ₃ level is highly dependent on Tb^3 + concentration, on presence of CdS co-dopant and annealing conditions.     

Judd–Ofelt theory: optical absorption and NIR emission spectral studies of Nd3+:CdO–Bi2O3–B2O3 glasses for laser applications

This article reports on the optical absorption and NIR emission properties of Nd³⁺ ions doped CdO–Bi₂O₃–B₂O₃ (CdBiB) glasses. Judd–Ofelt theory has been applied to calculate the oscillatory strengths of the transitions in the absorption spectra and also the intensity parameters Ω_λ (λ = 2, 4, and 6). These results were then used to compute the radiative properties of emission transitions of Nd³⁺:CdBiB glasses. From the NIR emission spectra of Nd³⁺:CdBiB glasses, three NIR emission bands are observed at 900, 1069, and 1338 nm and assigned to the transitions (⁴F_3/2 → ⁴I_9/2), (⁴F_3/2 → ⁴I_11/2), and (⁴F_3/2 → ⁴I_13/2), respectively. The concentration quenching phenomenon has also been explained. The stimulated emission cross-section and FWHM values were calculated for all the Nd³⁺:CdBiB glasses.     

Er–Pr tellurite glasses as promising materials for white light emitting diodes

The glass samples with composition TeO₂–WO₃–PbO–xEr₂O₃–yPr₆O₁₁ (x = 0,30%mol, y = 0,07%mol) were synthesized and studied with respect to the light emitting features. These glasses possess high photothermal stability and resistance against crystallization during reheating. The observed fluorescent spectra cover a wide visible spectral range. Due to simultaneous presence of both Er³⁺ and Pr³⁺ ions in the glass, nearly all absorption peaks are strongly overlapping. Careful analysis of the emission spectra allowed to assign all the observed peaks. From comparison of the Er³⁺ and Pr³⁺ ions’ energy level schemes, possible energy transfer processes were identified. The prepared glasses possess high quantum efficiency, which allow use them for white light emitting diodes.     

Study of structure and properties of ZnO–Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>–P<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

Glasses of the ternary system ZnO–Bi₂O₃–P₂O₅ were prepared and studied in two compositional series 50ZnO–xBi₂O₃–(50 − x)P₂O₅ and (50 − y)ZnO–yBi₂O₃–50P₂O₅. Two distinct glass-forming regions were found in the 50ZnO–xBi₂O₃–(50 − x)P₂O₅ glass series with x = 0–10 and 20–35 mol.% Bi₂O₃. All prepared Bi₂O₃-containing glasses reveal a high chemical durability. Small additions of Bi₂O₃ (∼5 mol.%) improve thermal stability of glasses. All glasses crystallize on heating within the temperature range of 505–583 °C. Structural studies by Raman and ³¹P MAS NMR spectroscopies showed the rapid depolymerisation of phosphate chains within the first region with x = 0–15 and the presence of isolated Q⁰ phosphate units within the second region with x = 20–35. Raman studies showed that bismuth is incorporated in the glass structure in BiO₆ units and their vibrational bands were observed within the spectral region of 350–700 cm⁻¹. The evolution of properties and the spectroscopic data are both in accordance with a network former effect of Bi₂O₃.     

Thermal-lens study of thermo-optical properties of tellurite glasses

Mode-mismatched Thermal Lens (TL) measurements were performed in 70TeO₂–19WO₃–7Na₂O–4Nb₂O₅ (% mol) tellurite glasses doped with either Er³⁺ or Tm³⁺ and co-doped with Er³⁺/Tm³⁺ ions. Thermo-optical parameters (D, K, ds/dQ and ds/dT) were obtained in function of thulium concentrations (0.39–1.6) × 10 ²⁰ ions/cm³. For Er³⁺/Tm³⁺ co-doped tellurite glasses, D and K values are practically independent of the Tm³⁺ concentrations used in this study. The average values of D and ds/dT obtained for tellurite glasses are: (3.1 ± 0.2) × 10⁻³ cm²/s and (16 ± 3) × 10⁻⁶ K⁻¹, respectively.     

Spectroscopic properties of Nd<Superscript>3+</Superscript>, Yb<Superscript>3+</Superscript>-doped and Nd<Superscript>3+</Superscript>–Yb<Superscript>3+</Superscript>-codoped high silica glass

The Nd³⁺, Yb³⁺-doped and Nd³⁺–Yb³⁺-codoped high silica glasses (HSGs) were fabricated by sintering porous glasses impregnated with Nd³⁺ and Yb³⁺ ions solutions. The Judd–Ofelt theory was used to study the spectroscopic properties of Nd³⁺-doped HSGs. Large parameter Ω₂ of Nd³⁺-doped HSGs suggests a lower centrosymmetric coordination environment around the Nd³⁺ in HSG. The spontaneous emission probability and emission cross-section (σ_em) of Yb³⁺-doped HSGs are obtained. A broad emission band from 950 to 1,100 nm was detected when the Nd³⁺–Yb³⁺-codoped HSG was excited by 808 nm LD. The energy transfer process from Nd³⁺ to Yb³⁺ in HSG was described in this paper.     

AC conductivity in rare earth ions doped vanadophosphate glasses

Room temperature density and AC conductivity in the temperature range 300–525 K and frequency range 50 Hz to 5 MHz have been investigated in a set of La₂O doped vanadophosphate glasses. The density decreased and total conductivity increased with increase of La₂O content. The high temperature electrical conductivity has been analyzed using Mott’s small polaron model and polaron activation energies were determined. The polaron activation energy decreased marginally with increase of lanthanum content, at all frequencies of interest. These results have been attributed to the presence of mixed ion–polaron conduction in the present glasses. It is for the first time that La₂O doped vanadophosphate glasses have been investigated for AC conductivity and despite heaviness of lanthanum ions, the mixed ion–polaron conduction has been detected. Frequency dependence of AC conductivity has been considered under the correlated barrier hopping (CBH) model of single electron hopping.     

Acoustic investigations on PbO-Al2O3-B2O3 glasses doped with certain rare earth ions

Elastic moduli (Y, η), Poisson’s ratio (σ), microhardness (H) and some thermodynamical parameters such as Debye temperature (θ_D), diffusion constant (D _i),latent heat of melting (ΔH _m) etc of PbO-Al₂O₃-B₂O₃ glasses doped with rare earth ions viz. Pr³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Tb³⁺, Dy³⁺, Ho³⁺, Er³⁺ and Yb³⁺, are studied as functions of temperatures (in the temperature range 30–200°C) by ultrasonic techniques. All these parameters are found to increase with increasing atomic numberZ of the rare earth ions and found to decrease with increasing temperature of measurement. From these results (together with IR spectra of these glasses), an attempt is made to throw some light on the mechanical strength of these glasses.     

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.     

Crystallization of CaHf1? x Zr x Ti2O7 (0?≤ x ≤?1) zirconolite in SiO2–Al2O3–CaO–Na2O–TiO2–HfO2–ZrO2–Nd2O3 glasses

Glass-ceramics containing (Hf,Zr)-zirconolite crystals (nominally CaHf_1−x Zr _x Ti₂O₇ with 0 ≤ x ≤ 1) were envisaged to immobilize minor actinides and plutonium. Such materials were prepared in this study by controlled crystallization of glasses belonging to the SiO₂–Al₂O₃–CaO–Na₂O–TiO₂–HfO₂–ZrO₂–Nd₂O₃ system. Neodymium was used as trivalent actinides surrogate. The effect of total or partial substitution of ZrO₂ by HfO₂ (neutron poison for fission reactions) on glass crystallization in the bulk and near the surface is presented. It appeared that Hf/Zr substitution had not significant effect on nature, structure, and composition of crystals formed both on glass surface (titanite + anorthite) and in the bulk (zirconolite). This result can be explained by the close properties of Zr⁴⁺ and Hf⁴⁺ ions and by their similar structural role in glass structure. However, strong differences were observed between the nucleation rate I_Z of zirconolite crystals in glasses containing only HfO₂ and in glasses containing only ZrO₂. Hf-zirconolite (CaHfTi₂O₇) crystals were shown to nucleate only very slowly in comparison with Zr-zirconolite (CaZrTi₂O₇) crystals. Composition changes - by increasing either HfO₂ or Al₂O₃ concentration or by introducing ZrO₂ in parent glass - were performed to increase I_Z in hafnium-rich glasses. The proportion of Nd³⁺ ions incorporated in the zirconolite phase was estimated using ESR.     

Structural investigation of rapidly quenched Li3BO3−Li4GeO4 glasses

Glasses were prepared in the pseudobinary system Li₃B0₃–Li₄GeO₄ by a rapid quenching technique in the composition range of 8–80 mol% Li₄GeO₄. The structure of the glasses was examined by Raman spectra, X-ray diffraction analysis and molecular dynamics simulation. The coordination number of germanium atoms with respect to oxygen atoms in the glasses Li₃B0₃–Li₄GeO₄ was shown to be higher than four by the X-ray diffraction analysis. The Raman spectra showed that not only monomer ions of BO ₃ ^–3 and GeO ₄ ^–4 , but also dimer B₂O ₅ ^–4 ions and six-coordinated GeO ₆ ^–8 ions were present in these glasses over the whole glass-forming region. The presence of these ions was also confirmed from molecular dynamics simulation.     

Effect of Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> on the dynamics of Li<Superscript>+</Superscript> ions in Li<Subscript>2</Subscript>O·P<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

Lithium ion transport has been studied in bismuth lithium phosphate glasses in the frequency range 20 Hz–1 MHz and in the temperature range 423–573 K using impedance spectroscopy. The addition of Bi₂O₃ in Li₂O·P₂O₅ glass is related to the modification of the glass structure and facilitates the Li⁺ ions migration. The ac and dc conductivities, activation energy of the dc conductivity and relaxation frequency are extracted from the impedance spectra. Conductivity of the present glass system is found to be ionic in nature. The electrical response of the glasses has been studied using both conductivity and electric modulus formalisms. A single ‘master curve’ for normalized plots of all the modulus isotherms observed for a given composition indicates the temperature independence of the dynamic processes for ions in these glasses. Nearly identical values of activation energy for dc conduction and for conductivity relaxation time indicate that the ions overcome same energy barrier while conducting and relaxing.     

Interactions of gamma rays with tungsten-doped lead phosphate glasses

Undoped lead phosphate glass of the composition PbO 50 mol%, P₂O₅ 50 mol% together with samples of the same ratio doped with various WO₃ contents were prepared. UV–Visible spectroscopic studies were measured out in the range 200–1100 nm before and after successive gamma irradiation. Infrared and Raman spectroscopic measurements were carried out for the undoped and WO₃-doped samples. All the prepared samples are observed to absorb strongly in the UV region due to the combined contributions of absorption from trace iron impurities and sharing of lead Pb²⁺ ions. The bluish WO₃-doped lead phosphate samples reveal visible absorption bands which are attributed to the existence of pentavalent W⁵⁺ ions. ESR measurements support this assumption. Infrared and Raman spectra indicate the presence of metaphosphate chains as the structural main building units and the possible presence of appreciable pentavalent (W⁵⁺O₃) of W⁵⁺ units together with hexavalent WO₄ units. Gamma irradiation reveal the shielding behaviour of the studied tungsten-doped lead phosphate glasses due to the combined presence of heavy Pb²⁺ ions and tungsten ions.     

Synthesis of Er<Superscript>3+</Superscript> and Er<Superscript>3+</Superscript> : Yb<Subscript>3+</Subscript> doped sol-gel derived silica glass and studies on their optical properties

Er₃₊ and Er₃₊ : Yb₃₊ doped optical quality, crack and bubble free glasses for possible use in making laser material have been prepared successfully through sol-gel route. The thermal and optical, including UV-visible absorption, FTIR etc characterizations were undertaken on the samples. The absorption characteristics of Er₃₊ doped samples clearly revealed the absorption due to Er₃₊ ions. On the other hand Yb₃₊ : Er₃₊ doped samples showed enhanced absorption due to² F _7/2 →² F _5/2 transition. The absorption and emission cross-section for² F _7/2 ↔² F _5/2 of Yb³⁺ were estimated. FTIR absorption spectra have clearly shown the reduction of the absorption peak intensity with heat treatment in the range 3700–2900 cm⁻¹. The 960 cm^-1 band also showed progressive decrease in the absorption band peak intensity with heat treatment. The result of the investigations with essential discussions and conclusions have been reported in this paper.     

In situ diffraction studies of magnesium silicate liquids

Primitive MgO–SiO₂ liquids dominate the early history of the Earth and Terrestrial planets. The structures of these liquids and structure-dependent properties, such as viscosity and diffusion, are considered important in the evolution of these planets, however, MgO–SiO₂ liquids are refractory and do not form glasses easily and it is difficult to measure the structure of these liquids. Container-less synthesis techniques have been used to produce glasses that range in composition from 50 to 33% SiO₂, corresponding to the compositions of two important mantle minerals: enstatite and forsterite. The structure of these glasses has been determined using combined neutron and high-energy diffraction and show changes in the short-range order as a function of composition. These changes include a jump in Mg–O coordination number at the limit to the formation of the silicate network in forsterite composition glass. These results imply a similar change in the structure of the liquid. Accordingly, the structures of forsterite and enstatite liquids have been determined using high-energy X-rays and a specialized sample environment, a containerless levitator. The main qualitative structural differences between MgSiO₃ and Mg₂SiO₄ glasses are also observed in the melt. Liquid MgSiO₃ is interpreted as forming a relatively ‘strong’ network of SiO₄ tetrahedra, whereas the Mg₂SiO₄ liquid is “fragile” and dominated MgO _n (n = 4, 5, 6) polyhedra and highly mobile oxygen ions. The results differ significantly from previously reported X-ray diffraction data for liquid MgSiO₃.     

Glasses and glass-ceramics in the SrO–TiO2–Al2O3–SiO2–B2O3 system and the effect of P2O5 additions

The glass formation abilities of various compositions in SrO–TiO₂–Al₂O₃–SiO₂, SrO–TiO₂–B₂O₃–SiO₂, SrO–TiO₂–Al₂O₃–B₂O₃, and SrO–TiO₂–Al₂O₃–SiO₂–B₂O₃ systems were studied. Many new compositions were found to be suitable for the casting of crack-free, optically clear glasses of different color and with glass transition temperatures ranging from 595 to 775 °C. The crystallization behavior, structure, and thermal expansion behavior of selected glasses were analyzed by DTA, XRD, dilatometry, and heat treatment. The effect of P₂O₅ on the glass structure and crystallization behavior was also studied. P₂O₅ played a dual role depending on composition. In some glasses it acted as a nucleating agent while in others it suppressed crystallization. Heat treatment of borate and borosilicate glasses transformed them into glass-ceramics while comparable SrO–TiO₂–Al₂O₃–SiO₂ glasses showed a lower tendency to crystallize and form glass-ceramics under the same conditions.     

Effect of Al2O3 concentration on zirconolite (Ca(Zr,Hf)Ti2O7) crystallization in (TiO2,ZrO2,HfO2)-rich SiO2–Al2O3–CaO–Na2O glasses

Glass-ceramic matrices containing zirconolite (nominally Ca(Zr,Hf)Ti₂O₇) crystals in their bulk that would incorporate high proportions of minor actinides (Np, Am, Cm) or plutonium could be envisaged for their immobilization. Zirconolite-based glass-ceramics can be prepared by controlled crystallization of zirconolite in glasses belonging to SiO₂–Al₂O₃–CaO–Na₂O–TiO₂–ZrO₂–HfO₂ system. In this study, neodymium was used as trivalent actinides surrogate. Increasing Al₂O₃ concentration in glass composition had a strong effect on the nucleation rate I _z of zirconolite crystals in the bulk, on the amount of neodymium incorporated in zirconolite phase and on the crystal growth rate of silicate phases (titanite + anorthite) from glass surface. These results could be explained by the existence of competition—in favor of aluminum—between Al³⁺ and (Ti⁴⁺, Zr⁴⁺, Hf⁴⁺) ions for their association with charge compensators cations to facilitate their incorporation in the glassy network. Differential thermal analysis (DTA) was used to study exothermal effects associated with bulk and surface crystallization. ²⁷Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectra showed that aluminum enters glasses network predominantly in 4-fold coordination. Neodymium optical absorption and fluorescence spectroscopies showed that the Al₂O₃ concentration changes performed in this study had not significant effect on Nd³⁺ ions environment in glasses.     

Studies on tin oxide films prepared by electron beam evaporation and spray pyrolysis methods

Transparent conducting tin oxide thin films have been prepared by electron beam evaporation and spray pyrolysis methods. Structural, optical and electrical properties were studied under different preparation conditions like substrate temperature, solution flow rate and rate of deposition. Resistivity of undoped evaporated films varied from 2.65 × 10⁻² ω-cm to 3.57 × 10⁻³ ω-cm in the temperature range 150–200°C. For undoped spray pyrolyzed films, the resistivity was observed to be in the range 1.2 × 10⁻¹ to 1.69 × 10⁻² ω-cm in the temperature range 250–370° C. Hall effect measurements indicated that the mobility as well as carrier concentration of evaporated films were greater than that of spray deposited films. The lowest resistivity for antimony doped tin oxide film was found to be 7.74 × 10⁻⁴ ω-cm, which was deposited at 350°C with 0.26 g of SbCl₃ and 4 g of SnCl₄ (SbCl₃/SnCl₄ = 0.065). Evaporated films were found to be amorphous in the temperature range up to 200°C, whereas spray pyrolyzed films prepared at substrate temperature of 300– 370°C were poly crystalline. The morphology of tin oxide films was studied using SEM.