Spectroscopic and magnetic studies of manganese ions in ZnO-Sb2O3-B2O3 glass system

ZnO-Sb₂O₃-B₂O₃ glasses containing different concentrations of MnO ranging from 0 to 1.0 mol% were prepared. A number of studies, viz. optical absorption, infrared and ESR spectra and magnetic susceptibility, were carried out as a function of manganese ion concentration. The analysis of the results indicate that manganese ions mostly exist in Mn²⁺ state in these glasses when the concentration of MnO≤0.6 mol% and above this concentration, these ions seem to exist in Mn³⁺ state in the glass network.     

Nickel ion—A structural probe in BaO-Al2O3-P2O5 glass system by means of dielectric, spectroscopic and magnetic studies

BaO-Al₂O₃-P₂O₅ glasses containing different concentrations of NiO (ranging from 0 to 1.0 mol%) were prepared. A number of studies viz., chemical durability, differential thermal analysis, spectroscopic (infrared, optical absorption spectra), magnetic susceptibility and dielectric properties (constant ε′, loss tan δ, AC conductivity σ_AC over a range of frequency and temperature) of these glasses have been carried out. The studies on chemical durability indicate that there is a significant increase in the corrosion resistance of the glasses; where as the results of differential thermal analysis suggests that there is a substantial improvement in the glass forming ability, with increase in the concentration of NiO up to 0.6 mol% in the glass matrix. The optical absorption, magnetic susceptibility and IR spectral studies point out nickel ions occupy both tetrahedral and octahedral positions in the glass network; the later positions seems to be dominant when the concentration of NiO is beyond 0.6 mol% in the glass matrix. The studies of dielectric properties reveal that the presence of nickel oxide in the glass network causes a considerable improvement in the insulating strength of the se glasses when the concentration of NiO?0.6 mol%.     

Role of manganese ions on the stability of ZnF2-P2O5-TeO2 glass system by the study of dielectric dispersion and some other physical properties

ZnF₂-P₂O₅-TeO₂ glasses containing different concentrations of MnO (ranging from 0 to 0.6%) were prepared. A number of studies, viz. differential thermal analysis, optical absorption, thermo luminescence, infrared spectra, magnetic susceptibility, elastic properties (Young's modulus Y, shear modulus n and micro hardness H) and dielectric properties (constant ε, loss tan δ, a.c. conductivity σ_ac over a range of frequency and temperature and dielectric breakdown strength), of these glasses were carried out as a function of manganese ion concentration. The analysis of the results indicate manganese ions mostly exist in Mn²⁺ state in these glasses when the concentration of MnO≤0.4% and above this concentration manganese ions predominantly exist in Mn³⁺ state; from this analysis an attempt is made to identify the role of these ions on the stability of glass network.     

Dielectric dispersion in PbO-Sb2O3-As2O3:V2O5 glasses

Dielectric properties, viz. dielectric constant ε′, loss tan δ and a.c conductivity σ_ac (over a wide range of frequency and temperature) and dielectric breakdown strength of PbO-Sb₂O₃-As₂O₃ glasses doped with V₂O₅ (ranging from 0 to 0.5 mol%) are studied. Analysis of these results, based on optical absorption and ESR spectra, indicates that the insulating strength of the glasses is comparatively high when the concentration of V₂O₅ is about 0.3 mol% in the glass matrix.     

Optical absorption and thermoluminescence studies on LiF-Sb2O3-B2O3 glasses doped with Ni ions

20LiF-(30−x)Sb₂O₃-50B₂O₃:xNiO glasses with the value of x (ranging from 0 to 1.0 mol% in steps of 0.2) were prepared. A number of studies, viz. differential scanning calorimetry, optical absorption, magnetic susceptibility and thermoluminescence, on these glasses were carried out as a function of nickel ion concentration. An anomaly has been observed in all the properties of these glasses when NiO concentration is about 0.6 mol%. The results of these studies were analysed in the light of different environments of nickel ions in the glass network.     

EPR and magnetic susceptibility studies of iron ions in ZnO-Fe2O3-SiO2-CaO-P2O5-Na2O glasses

Room temperature electron paramagnetic resonance (EPR) spectra and temperature dependent magnetic susceptibility data have been obtained on bulk x(ZnO,Fe₂O₃)(65−x)SiO₂20(CaO, P₂O₅)15Na₂O (6≤x≤21 mole%) glasses prepared by melt quenching method. EPR spectra of the glasses revealed absorptions centered at g≈2.1 and 4.3. The variations of the intensity and line width of these absorption lines with composition have been interpreted in terms of the variation in the concentration of the Fe²⁺ and Fe³⁺ ions in the glass and the interaction between the iron ions. EPR and magnetic susceptibility data of the glasses reveal that both Fe²⁺ and Fe³⁺ ions are present in the glasses, with their relative concentration being dependent on the glass composition. The studies reveal superexchange type interactions in these glasses, which are strongly dependent on their iron content.     

Electrical behaviour of Li2O-ZnO-SiO2 glass and glass-ceramics system

Sealing quality lithium zinc silicate (LZS) glasses of compositions (wt.%) (a) LZSL- Li₂O: 12.65, ZnO: 1.85, SiO₂: 74.4, Al₂O₃: 3.8, K₂O: 2.95, P₂O₅: 3.15, B₂O₃: 1.2 (low ZnO), and (b) LZSH- Li₂O: 8.9, ZnO: 24.03, SiO₂: 53.7, Na₂O: 5.42, P₂O₅: 2.95, B₂O₃: 5 (high ZnO) were prepared by conventional melt-quench technique and converted to glass-ceramics by controlled crystallization process. The electrical properties of these samples were measured using ac impedance spectroscopy technique over a frequency range of 10 Hz-15 MHz at several temperatures in the range of 323-673 K. The ac conductivity, dc conductivity, dielectric constant and loss factor were obtained from these measurements. The dc conductivity (σ_dc) follows the Arrhenius behaviour with temperature. It is observed that σ_dc in LZSL glass is significantly higher than in the LSZH glass and the activation energies for σ_dc for LZSL and LZSH glasses are 0.59 and 1.08 eV, respectively. It further observed that the conductivity value decreases nearly one order of magnitude on conversion to glass-ceramics. The behaviour is explained on the basis of distributions and nature of alkali ions and network structures in these samples.     

In vitro evaluation of bioactivity of CaO-SiO2-P2O5-Na2O-Fe2O3 glasses

Glasses with compositions 41CaO(52 − x)SiO₂4P₂O₅·xFe₂O₃3Na₂O (2 ≤ x ≤ 10 mol.%) were prepared by melt quenching method. Bioactivity of the different glass compositions was studied in vitro by treating them with simulated body fluid (SBF). The glasses treated for various time periods in SBF were evaluated by examining apatite formation on their surface using grazing incidence X-ray diffraction, Fourier transform infrared reflection spectroscopy, scanning electron microscopy and energy dispersive spectroscopy techniques. Increase in bioactivity with increasing iron oxide content was observed. The results have been used to understand the evolution of the apatite surface layer as a function of immersion time in SBF and glass composition.     

Investigation on spectral features of tungsten ions in PbO-Bi2O3-As2O3 glass matrix

Lead bismuth arsenate glasses mixed with different concentrations of WO₃ (ranging from 0 to 6.0 mol%) were synthesized. Differential thermal analysis (DTA), optical absorption, ESR and IR spectral studies have been carried out. The results of DTA have indicated that there is a gradual decrease in the resistance of the glass against devitrification with increase in the concentration of WO₃ upto 4.0 mol%.The optical absorption spectra of these glasses exhibited a relatively broad band peaking at about 880 nm identified due to d_xy→d_x²_−y² transition of W⁵⁺ ions; this band is observed to be more intense in the spectrum of glass containing 4.0 mol% of WO₃. Further, two prominent kinks attributed to ³P₀→¹S₀, ¹D₂ transitions of Bi³⁺ ions have also been located in the absorption spectra. The ESR spectra of these glasses recorded at room temperature exhibited an asymmetric signal at g_⊥∼1.71 and g_ll∼1.61. The intensity of the signal is observed to be maximal for the spectrum of the glass W₄. The quantitative analysis of optical absorption and ESR spectral studies have indicated that there is a maximum reduction of tungsten ions from W⁶⁺ state to W⁵⁺ state in the glass containing 4.0 mol% of WO₃. The IR spectral studies have indicated that there is a increasing degree of disorder in the glass network with increase in the concentration of WO₃ upto 4.0 mol%.     

The magnetic susceptibility of hydrogen-doped partially crystalline (Zr76Ni24)1−xHx metallic glasses

The magnetizations of Zr₇₆Ni₂₄ metallic glass and hydrogen-doped partially crystalline (Zr₇₆Ni₂₄)_1−xH_x metallic glasses have been measured in the temperature range 10-300 K and magnetic fields up to 2 T for various dopant concentrations (x=0, 0.024, 0.043, 0.054). It is found that the samples are paramagnetic and magnetic susceptibility at room temperature, χ(300 K), shows a nonmonotonic behaviour upon hydrogenation. The values of χ(300 K) of the hydrogen-doped partially crystalline (Zr₇₆Ni₂₄)_1−xH_x metallic glasses are reduced with increase in hydrogen content up to x=0.043, whereas for x=0.054, an enhancement of χ(300 K) has been revealed. The magnetic susceptibility is weakly temperature dependent down to 110 K, below which an increase is observed. A shallow minimum exists between 90 and 120 K. The form and magnitude of the observed temperature dependence of the magnetic susceptibility are well accounted for by the sum of the quantum corrections to the magnetic susceptibility. Hydrogen reduces the electronic diffusion constant and influences strongly the quantum interference at defects, slowing down the spin diffusion and enhancing the magnetic susceptibility in the temperature range from 110 down to 10 K.     

Microstructural, dielectric and spectroscopic properties of Li2O-Nb2O5-ZrO2-SiO2 glass system crystallized with V2O5

Li₂O-Nb₂O₅-ZrO₂-SiO₂ glasses mixed with different concentrations of V₂O₅ were crystallized. The samples were characterized by XRD, SEM and DTA techniques. The SEM pictures indicated that the samples contain well defined and randomly distributed crystal grains. The X-ray diffraction studies have revealed the presence of several crystalline phases in these samples. Optical absorption, ESR and photoluminescence spectral studies on these samples have indicated that a considerable proportion of vanadium ions do exist in V⁴⁺ state in addition to V⁵⁺ state and the redox ratio seems to be increasing with increase in the concentration of crystallizing agent V₂O₅. The infrared spectral studies have pointed out the existence of conventional SiO₄, ZrO₄, NbO₆, VO structural units in the glass ceramic network. The study of dielectric properties suggested a decrease in the insulating character of the glass ceramics with increase in the crystallizing agent. A.C. conductivity in the high temperature region seems to be connected mainly with the polarons involved in the process of transfer from V⁴⁺↔V⁵⁺ ions.     

Study of PbO-SrO-TiO2-B2O3 glass and glass ceramics

The glasses with composition (50−X)PbO–XSrO-25TiO₂-25B₂O₃ (where X=0, 5, 10 and 15 mol%) were prepared using conventional quenching technique. The T_g, T_c, density and CTE of the glass samples were measured. The T_g observed to increase with increasing concentration of SrO, while the T_c first decreased and then increased. The glass samples were converted to glass ceramics by following two stage heat treatment schedule. The glass ceramic samples were characterized by XRD, SEM and dielectric measurements. The XRD results revealed the formation of ferroelectric lead titanate as a major crystalline phase in glass ceramics. Additional phases observed include Sr₂B₂O₅ and PbB₂O₄. The room temperature (RT) dielectric constant of glass and glass ceramics are in the range of 100–120 which is promising for capacitor application.     

The role of iron ions on the structure and certain physical properties of PbO-As2O3 glasses

Various studies have been carried out viz optical absorption, infrared spectra, magnetic susceptibility, dielectric parameters (dielectric constant, loss and a.c. conductivity over a range of frequency and temperature; and breakdown strength) and differential thermal analysis of PbO-As₂O₃ glasses containing 0-1 mol% of Fe₂O₃. An anomaly has been observed in all the properties of these glasses when Fe₂O₃ concentration is about 0.25 mol%. The reasons for such anomaly have been identified and found that PbO-As₂O₃ glasses are more stable when Fe₂O₃ concentration is about 0.25 mol%.     

EPR and magnetic properties of MgO-CaO-SiO2-P2O5-CaF2-Fe2O3 glass-ceramics

Glass-ceramics have been derived from 4.5MgO(45−x)CaO34SiO₂16P₂O₅0.5CaF₂xFe₂O₃ (x=5, 10, 15, 20 wt%) glasses by heat treatment. Room temperature electron paramagnetic resonance (EPR) spectra and temperature-dependent magnetic susceptibility (χ) of the glass-ceramics have been obtained. The EPR absorption line centered at g≈4.3 disappeared at higher concentrations of iron oxide. The intensity and line width of the EPR absorption line centered at g≈2.1 increased as the iron oxide concentration was increased. Temperature-dependent magnetization of samples with low iron oxide content revealed ferrimagnetic as well as paramagnetic contributions. Information about the structural changes involving iron ions, their valence state and the type of magnetic interactions between the Fe ions as a function of composition was obtained using EPR and χ studies.     

Comparative investigation on spectroscopic properties of Er between Ce-doped and B2O3-added bismuth glasses

The comparative investigation on the spectroscopic properties of Er³⁺ in low phonon energy Bi₂O₃-GeO₂-Ga₂O₃-Na₂O glasses codoped with Ce³⁺ ion and added with B₂O₃ component, respectively, is presented. With increasing Ce₂O₃ content from 0 to 0.8 mol% or B₂O₃ content from 0 to 15 mol%, the lifetime of Er³⁺:⁴I_11/2 level decreases dramatically from 607 to 283 μs or to 197 μs, and the upconversion fluorescence is quenched in both glass samples. The nonradiative energy transfer from Er³⁺:⁴I_11/2→Ce³⁺:²F_5/2 or the enhanced multiphonon relaxation process together with the energy transfer between Er³⁺ and OH⁻ groups are, respectively, responsible for the results. Meanwhile, the lifetime of ⁴I_13/2 level remains almost unchanged in Er³⁺/Ce³⁺-codoped glasses whereas it decreases rapidly in B₂O₃-added cases. As a result, Er³⁺/Ce³⁺ codoping improves the 1.5 μm fluorescence emission intensity, however, B₂O₃ addition has a negative effect on it. The research results indicate that the Er³⁺/Ce³⁺-codoped bismuth glasses will be preferable for obtaining efficient 980 nm pumped EDFA.     

Effect of ZnO/CdO on the structure and electrical conductivity in Li2O·MO·Bi2O3·B2O3 glasses (M=Zn, Cd)

Studies of structural and electrical properties have been carried out on a number of glasses with wide ranging compositions in the glass systems Li₂O·MO·Bi₂O₃·B₂O₃ (where M=Zn or Cd), in order to understand the effect of transition metal (TM) ions on the structure of these glasses. The density and molar volume measurements have also been made to understand the structural changes occurring in these glasses. The dc conductivity measured in the temperature range 423-623 K obeys Arrhenius law. It increases with increase in Li₂O/MO ratio. The results of infrared spectra indicate that TM ions (Zn²⁺ or Cd²⁺) behave as network former in the present system. Boron exists in both tri- and tetra-hedral units in these glasses and no boroxol ring formation takes place in the glass structure. Values of theoretical optical basicity have also been reported.     

Emission analysis of Dy and Pr:Bi2O3-ZnF2-B2O3-Li2O-Na2O glasses

In this paper, we present the spectral results of Dy³⁺ and Pr³⁺ (1.0 mol%) ions doped Bi₂O₃-ZnF₂-B₂O₃-Li₂O-Na₂O glasses. Measurements of X-ray diffraction (XRD), differential scanning calorimetry (DSC) profiles of these rare-earth ions doped glasses have been carried out. From the DSC thermograms, glass transition (T_g), crystallization (T_c) and melting (T_m) temperatures have been evaluated. The direct and indirect optical band gaps have been calculated based on the glasses UV absorption spectra. The emission spectrum of Dy³⁺:glass has shown two emission transitions ⁴F_7/2→⁶H_15/2 (482 nm) and ⁴F_7/2→⁶H_13/2 (576 nm) with an excitation at 390 nm wavelength and Pr³⁺:glass has shown a strong emission transition ¹D₂→³H₄ (610 nm) with an excitation at 445 nm. Upon exposure to UV radiation, Dy³⁺ and Pr³⁺ glasses have shown bright yellow and reddish colors, respectively, from their surfaces.     

Photoinduced second-order optical susceptibilities of Er2O3 doped TeO2-GeO2-PbO glasses

Second-order optical susceptibilities were established in the optically poled erbium doped tellurite glasses near the melting temperature. The non-linear optical susceptibility was formed by bicolor coherent optical treatment performed by two coherent laser beams originated from 50 ps Nd-YAG laser (λ = 1.32 μm) exciting the high pressure hydrogen laser cell emitting at 1907 nm. The non-centrosymmetric grating of the medium was created by coherent superposition of the fundamental laser illumination at 1907 nm and the doubled frequency one at 953.5 nm. The maximally all-optically poled SHG occurs for 2% doped Er₂O₃ (in weighting units) TeO₂-GeO₂-PbO glass. It was found that the photoinduced SHG demonstrates a saturation during the photo-treatment of 9-10 min using the two beams polarized at angle about 45° between them. During the coherent bicolor optical treatment it was achieved the value of second-order susceptibility up to 3.6 pm/V at 1907 nm. The optimal ratio between the fundamental beam with power density about 1.1 GW/cm² and writing doubled frequency seeding beam about 0.015 GW/cm² corresponds to the maximal of photoinduced SHG. For glasses with lower concentration of Er₂O₃, the relaxation of the second-order optical susceptibility is substantially longer and achieves SHG value that corresponds to 80% of the maximal ones. It is necessary to emphasize that efficient optically-poled grating exists only within the narrow temperature range near the glassing temperature. Possible physical mechanisms of the phenomenon observed are discussed. Generally the used glasses possess better parameters than early investigated germinate glasses.     

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.     

Ag concentration dependent transport properties of LiF-MoO3-P2O5 glasses

LiF-MoO₃-P₂O₅ glasses mixed with different concentrations of Ag₂O (ranging from 0 to 1.0 mol%) was prepared. D.C. conductivity and dielectric properties over a range of temperature have been investigated. The analysis of the results of d.c. conductivity has indicated that T>θ_D/2, the small polaron hoping model seems to be fit and the conduction is adiabatic in nature. These results further indicated that there is a change over of conduction mechanism from electronic to ionic at about 0.4 mol% of Ag₂O. The low temperature part of a.c. conductivity is explained based on quantum mechanical tunneling model. The quantitative analysis of these results is further extended with the aid of the data on optical absorption, ESR and IR spectral studies.