Li2B4O7 Glasses Research Articles

Impact of Bismuth (Bi2O3) on physical and spectroscopic studies ZnO–Li2B4O7 glasses modified with Gd3+ ions

The manuscript is to provide information about the preparation, identification of the glassy nature, primary physical parameters and structural studies of Bi2O3 – ZnO – Li2B4O7 – GdF3 glasses. The glasses of thickness around 1 mm were obtained by quenching the molten viscous material onto the moulds. These glasses are transparent enough to recognize them into glassy species but their amorphous nature was scientifically identified with peak free XRD spectra. Several properties like density, molar volume, optical absorption, FTIR, Raman and EPR spectra were measured, analyzed and discussed in detail. Density drastically increased from 2.7715 gm/cc (BZLG-0) to 4.9352 gm/cc (BZLG-40) nearly the increment is (Δρ = 2.1637 gm/cc) is attributed to the presence of bismuth. Molar volume declined to reach from 57.9366 (BZLG-0) to 56.5949 (BZLG-40) glass sample. Optical absorption spectra are flat with no absorption bands except edge transitions. With the concentration of bismuth going from low to high the optical band gap energy 3.281 eV (BZLG-0) shrinks to 2.825 eV (BZLG-40). The band gap decrement is associated with the formation of non-bridging oxygens. FTIR and Raman studies combinedly reveal the existence of certain structural groups and the domination of few borate modes. Observed EPR spectra have shown characteristic resonance signals of the so-called U spectrum typical for Gd3+ ions in disordered systems. In addition to the U-spectrum, an unexpected high crystal field resonance signal is also present.

Structural and spectroscopic studies of lithium tetraborate glass co-doped with Sm and Cu.

The local structure and spectroscopic properties of Cu-Sm co-doped Li2B4O7 glass have been studied using XRD, EPR, UV-Vis-NIR absorption and luminescence methods and compared with the corresponding results for Sm-doped and Cu-doped Li2B4O7 glasses. The EPR spectrum reveals an axially-symmetric signal with a characteristic hyperfine structure belonging to Cu2+ ions. The Cu2+/Cutotal ratio was determined. The optical absorption spectrum shows a broad, intense band attributed to Cu2+ ions and several weaker narrow bands attributed to Sm3+ ions. Photoluminescence (PL) and photoluminescence excitation (PLE) spectra as well as PL decay kinetics of Sm3+ and Cu+ ions were registered, analyzed, and discussed. The PL spectra show a broad band assigned to the 3d94s1 → 3d10 transition of Cu+ ions and four narrow bands assigned to the 4G5/2 → 6HJ (J = 5/2-11/2) transitions of Sm3+ ions. The observed changes in PL intensity, shortening of the Sm3+ lifetime and prolongation of the Cu+ lifetime were explained by energy transfer from Sm3+ → Cu+ and re-absorption of the Sm3+ emission by Cu2+ ions.

Impact of BaF2 on physical and spectroscopic studies of TeO2–Li2B4O7 glasses modified with Cu2+ ions

The present manuscript deals with the preparation and structural studies of BaF2–TeO2 – Li2B4O7–CuO glasses. The glasses were made using the melt quenching procedure, and their properties were examined utilizing the density, absorption, FTIR, Raman, and EPR spectra. The lack of strong peaks in the XRD spectra provides evidence that the phase is non-crystalline. The samples' densities went up but their molar volumes went down. The transition between 2B1g and 2B2g is responsible for a broad absorption band in optical absorption spectra. With BaF2, the band gap values obtained from the Tauc plot were raised. The density and optical data were used to determine a number of additional characteristics. The existence of various structural groups in the glass structure was shown by the FTIR and Raman spectra. Calculated from EPR spectra, the spin- Hamiltonian and bonding parameter values explained the ligand field around the Cu2+ ions.

Investigations on the role of doped 3d transition ions in Li2B4O7 glasses: Local structures, spectroscopic properties and optical basicities

Glasses with doped transition metal ions (TMs) have shown specific spectroscopic properties, but the micro-mechanism is hard to be obtained due to the amorphous structure. Based on the high order perturbation formulae of electron paramagnetic resonance (EPR) parameters, the local environment of 3d ions (V4+, Cr3+, Mn2+ and Cu2+) in Li2B4O7 glasses is studied to explain the experimental EPR spectra. The spectroscopic properties of Li2B4O7 glasses are closely correlated with the doped 3d ions, which can be reasonably predicted from the transition bands of divided energy orbitals. The crucial optical basicities of Li2B4O7 glasses doped with different TMs are also investigated, which are consistent with the above calculation results with respect to the local environment. The results show that TMs doping can be an effective way to modify the intrinsic properties of glasses.

Enhanced near-infrared luminescence at 1.07 μm of Nd3+ doped PbCl2–Li2B4O7 glasses for solid state laser and optical fiber amplifier applications

Abstract Nd3+ doped PbCl2–Li2B4O7 glasses have been synthesized using melt quenching technique. XRD spectra reveals the signature of non-crystalline behavior of synthesized glasses. DSC studies reveal glass transition temperature and thermal stability parameter (ΔT) exhibit composition dependent trends and ΔT is as high as 114 °C. UV–Vis spectra contain eleven well-defined absorption peaks with five intense absorption bands centered at 527, 586, 750, 806 and 876 nm which are assigned to transitions from 4I9/2 → 4G7/2, [4G5/2,2G7/2], [4F7/2, 4S3/2], [4F5/2, 2H9/2] and 4F3/2 respectively. The maximum absorption cross section 1 . 139 × 10 − 20 cm2 of 806 nm pump level transition 4I9/2 → [4F5/2, 2H9/2] is comparable with maximum absorption cross section 1 . 149 × 10 − 20 cm2 of 586 nm hypersensitive transition 4I9/2 → [4G5/2, 2G7/2]. Near infrared emission spectra exhibit very high emission intensity at 1070 nm for 4F3/2 → 4I11/2 transition along with two dominant emission bands at 904 and 1340 nm corresponding to 4F3/2 → 4I9/2 and 4F3/2 → 4I13/2 transitions. This high absorption and emission intensities are attributed to high degree of covalent environment of ligands surrounding Nd3+ ions. Bonding parameter, δ increase with Nd2O3 content which suggests dominance of covalency between Nd3+ ion and ligands. 11B MAS NMR studies reveal that, the addition of Nd2O3 to Li2B4O7 converts diborate units into chain-like network structures such as charged trigonal borate units which is further supported by FTIR study. Two photon absorption coefficient shows linear relationship with optical band gap energy. Hence Nd3+ doped PbCl2–Li2B4O7 glasses with superior absorption and emission properties are found to be potential candidates for near-infrared solid state laser and optical fiber amplifier applications.

Towards superior optical and dielectric properties of borosilicate glasses containing tungsten and vanadium ions

Transparent glasses of the composition (20–x)V2O5–xWO3–20SiO2–60Li2B4O7, x = 2, 4, 8 and 16 mol %, have been successfully synthesized by a popular melt quenching technique. The main features regarding the structure of these glasses were determined via Fourier transform infrared (FTIR) spectroscopy. The structure change was occurred in the glasses containing 8 and 16 mol% of WO3 which, in turn, decreased non-bridging oxygen (NBO) atoms with further WO3 additions. In addition, the density of these glasses provided higher values with WO3 additions. Optical measurements were achieved through different ranges of wavelength, revealing that the degree of transparency improved, while the absorption decreased, with WO3 additions. Remarkably, the optical transitions of tungsten and vanadium ions embedded in lithium borosilicate glasses were examined. The energy of optical band gaps was decreased by introducing WO3 until 8 mol %, and then increased with further WO3 additions. Furthermore, the conductivity was slightly increased by introducing WO3 until 8 mol %, and then decreased with further WO3 additions, whereas the activation energy demonstrated the opposite behavior with WO3 additions. The dependence of dielectric permittivity, dielectric loss and electrical conductivity on temperatures at varying frequencies was applied. The loss factor revealed a peak that moves towards higher temperature as the frequency increased, indicating the Debye-type relaxation behavior. Finally, the outcomes demonstrated that WO3–V2O5–SiO2–Li2B4O7 glasses are promising optically and electrically tunable materials.

Optical, structural and nuclear radiation shielding properties of Li2B4O7 glasses: effect of boron mineral additive

The glass samples with Li2B4O7 (100 − x) Tincalx (x = 0, 10, 20, 30 and 40 wt%) composition were synthesized by melt-quenching technique (Tincal = Na2B4O7·10H2O). The elemental analysis of Tincal with different compositions is tested using energy-dispersive X-ray technique. Moreover, the surface morphology of fabricated glasses was investigated with scanning electron microscopy. Further, optical properties of fabricated Tincal glasses were evaluated along the wavelength ranged from 200 to 900 nm. Finally, nuclear radiation shielding properties of Tincal glasses were determined for gamma rays, neutrons and charged particles. It is observed from the optical absorption spectra that Tincal 20% and 40% indicated good optical transparency in the visible range of light (400–700 nm). The results showed that Tincal additive improves the gamma protecting capacity of glasses. It was also noticed that the addition of Tincal was also enhanced the neutron absorption of the glasses by increasing the cross section of the neutron and reducing the coherent scattering length.

Synergistic effect of serpentine mineral on Li2B4O7 glasses: optical, structural and nuclear radiation shielding properties

The hypothesis of the present investigation underlined with determination of possible synergistic effects of serpentine mineral additive on Li2B4O7 glasses. A group of Li2B4O7 glasses with serpentine mineral additive were synthesized by melt-quenching technique. The elemental analysis of two different Li2B4O7 glasses with different amount of serpentine additive is tested using energy-dispersive X-ray (EDX) technique. Next, the surface morphology of synthesized serpentine glasses was investigated with scanning electron microscopy (SEM). The optical features of synthesized serpentine glasses were determined along the wavelength ranged from 200 to 900 nm. Lastly, nuclear radiation shielding properties of Li2B4O7 glasses with serpentine mineral additive were determined for gamma rays, neutrons and charged particles. MCNPX (version 2.6.0) general-purpose Monte Carlo code has been utilized for mass attenuation coefficients calculations. The results showed that the spectra are decreasing with wavelength with an observed peak centered at 450 nm. Moreover, it is observed that serpentine mineral additive improves the gamma protecting capacity of Li2B4O7 glasses. It was also noticed that the addition of serpentine mineral also enhanced the neutron and charged particle absorption of the glasses.

Self‐reduction of Eu3+ to Eu2+ in europium‐doped Li2B4O7 glass prepared in air

AbstractMotivated by the detection of neutrons, europium‐doped Li2B4O7 glasses enriched with both lithium and boron elements with high cross‐section capture were developed. A highly effective method of realizing the self‐reduction of Eu3+ to Eu2+ ions in europium‐doped Li2B4O7 glasses prepared by high temperature melt‐quenching technology in air was revealed. The self‐reduction of Eu3+ to Eu2+ ions can be easily achieved by the partial replacement of B2O3 with BN within 2 mol% concentration. And the effect of partially replacing B2O3 with BN on the optical properties of europium‐doped Li2B4O7 glass are systematically studied by transmittance, photoluminescence, and radioluminescence spectra, together with the luminescence decay curves.

Correlation between non-linear optical parameter and structure of Li2B4O7 glasses doped with [formula omitted]ions

The glass system 90Li2B4O7+xEr2O3+(10−x)BiCl3, where 0.1 ≤ x ≤ 0.5 mol%, has been synthesized by melt quenching technique. The Judd-Ofelt (JO) theory has been initiated for the precise analysis of the peak intensities. The JO parameter Ω2, which represents asymmetry and covalency of the emission environment increases with increase in Er3+ ions, while Ω4 and Ω6 reveal the rigidity of the host medium. Radiative parameters such as τR, AR, βR, FOM, and σR have been calculated. The photometric studies, CIE & CCT studies confirm that, for all the investigated glasses CIE coordinated diagram is found to be white light. CCT graph which gives white light emission around 10000K. Two photon absorption coefficient (TPA) of Er3+ doped glasses lie in the range of 7.491 to 8.868. Glasses with highest TPA shows low Eg values indicating a large density of states of O2− in highest occupied molecular orbitals.

An experimental study on gamma ray shielding features of lithium borate glasses doped with dolomite, hematite and goethite minerals

In this work, lithium borate (LB) glasses including dolomite, hematite and goethite minerals ((100-x) Li2B4O7-Mineral x = 10, 20, 30, 40 wt %) were produced with melt quenching technique. The densities (ρ, g/cm3) of the prepared glasses were determined with Archimedes method and the molar volumes (Vm, cm3/g) were calculated. XRD measurements were taken to control the amorphous structure of the glasses. To determine the shielding capabilities of the glasses under examination, mass attenuation coefficients (μρ,cm2/g) of mineral doped glasses at 81, 276, 302, 356, 383 keV photons emitted from 3 Ci 133Ba radioactive source have been defined by using HPGe detector. With the results acquired, the shielding parameters; effective atomic number (Zeff) and half value layer (HVL) were calculated experimentally and compared to the theoretical results obtained by using WinXCOM program. LB glasses containing goethite 30, 40% and hematite 40% have larger μ and Zeff and lower HVL values than the other prepared glasses. Furthermore, with Geometric Progression approach (GP-fitting), exposure buildup factor (EBF) values of the glasses were calculated in the 0.015–15 MeV energy range and up to 40 mean free path (mfp) penetration depth. Dolomite added glasses have larger EBF values than hematite and goethite added. But the transparency of dolomitic glass can make it worthwhile. Last of all, Li2B4O7 glasses including hematite and goethite have comparable and good radiation absorption properties.

Ionic Conductivity in Lithium-Borate-Tantalate Compound Glasses

We have investigated the ionic conductivity and dielectric relaxation in Li2B4O7 (LBO) and Li2OB2O3-Ta2O5 (LBTO) glasses. The sample was synthesized by using the melt quenching method. The frequency dependence of the electrical data from the LBO and LBTO glasses has been analyzed in the frameworks of the impedance Cole-Cole formalism and the universal power-law representation driven by the modified fractional Rayleigh equation. The potential barriers in the LBO and the LBTO glasses turn out to be the same. Comparing with the dc and ac activation energies of the LBO glass, these energies of the LBTO glass decrease due to the increasing Coulomb interaction of inter-cationic interaction.

Enhancement of the Er3+ luminescence in Er–Ag co-doped Li2B4O7 glasses

Luminescence properties of the Er-doped and Er–Ag co-doped glasses with Li2B4O7 (Li2O–2B2O3) basic composition are investigated and analysed. The Li2B4O7 glasses of high chemical purity and optical quality, doped with Er and co-doped with Er and Ag were obtained in the air using standard glass technology. Spectroscopic properties of the Li2B4O7:Er and Li2B4O7:Er,Ag glasses were studied using optical absorption and photoluminescence (excitation, emission, decay kinetics) experimental techniques as well as Judd–Ofelt analysis. The theoretical and experimental oscillator strengths for observed absorption transitions as well as Judd–Ofelt intensity parameters (Ω2, Ω4, Ω6) have been calculated. Photoluminescence spectra of the Li2B4O7:Er and Li2B4O7:Er,Ag glasses reveal intense infrared (4I13/2 → 4I15/2 transition, λmax = 1530 nm) and green (4S3/2 → 4I15/2 transition, λmax = 546 nm) emission bands. Radiative properties such as transition probabilities (Arad), luminescence branching ratios (β), stimulated emission cross-sections (σem), and radiative lifetimes (τrad) are estimated. Experimental and radiative lifetimes were compared and quantum efficiency (η) has been evaluated. Considerable enhancement of the Er3+ green luminescence in the Li2B4O7:Er,Ag glasses has been observed. The observed enhancement is attributed to energy transfer from Ag+ to Er3+ ions as well as local field effects induced by surface plasmon resonance of the silver metallic nanoparticles.

Enhancement of the Eu3+ luminescence in Li2B4O7 glasses co-doped with Eu and Ag

The luminescence properties of the Eu-doped and Eu-Ag co-doped glasses with Li2B4O7 (Li2O–2B2O3) basic composition are investigated and analysed. The Li2B4O7 glasses of high chemical purity and optical quality, doped with Eu and/or Ag were obtained in the air atmosphere using standard glass technology. Spectroscopic properties of the obtained Li2B4O7:Eu and Li2B4O7:Eu,Ag glasses were studied using optical absorption, photoluminescence (excitation, emission, decay kinetics), and quantum yield measurements. Photoluminescence spectra of the Li2B4O7:Eu glass reveal emission bands, which correspond to the 5D0 → 7FJ (J = 0 – 6) transitions of Eu3+ ions. The enhancement of Eu3+ luminescence in the Li2B4O7:Eu,Ag glass have been observed. The external quantum yield (QY) of luminescence was measured via an absolute method. The QY of Eu3+ luminescence increases from 11.7% to 26.1% in the Li2B4O7:Eu,Ag glass in comparison with Li2B4O7:Eu glass. Such enhancement is attributed to the energy transfer from Ag+ ions and very small molecule-like non-plasmonic silver aggregates to the Eu3+ ions as the major factor, and local field effects induced by surface plasmon resonance of the silver nanoparticles. The obtained high external quantum yield shows that the Li2B4O7:Eu,Ag glasses belong to perspective luminescent materials.

Role of Er3+ and Bi3+ ions on thermal and optical properties of Li2B4O7 glasses: Structural correlation

Glasses with general formulae xBiCl3-(100-x)Li2B4O7 where 10 ≤ x ≤ 30 and x Er2O3-(10-x)BiCl3-90Li2B4O7, where 0.1 ≤ x ≤ 0.5 mol% have been prepared to study the effect of Er2O3/BiCl3 on their physical, thermal and optical properties. Thermal stability parameter (∆T) extracted from DSC thermograms reveals that the ∆T (>100°C) depends on Er2O3 content and the glasses are suitable for fiber drawing process. Optical properties of both the investigated glass systems exhibit composition dependent trends and the properties are critically dependent on polarizabilities and ionicity of the dopant ions. The variations observed in the physical properties of investigated glasses were correlated to the structural changes occur due to the addition of BiCl3/Er2O3. 11B MAS NMR studies reveal the opening up of a tightly bound [B4O7]2− structural units with the formation of NBOs in the network. The variation of N4 (fraction of 4-coordinated boron to the total boron content) with BiCl3/Er2O3 clearly indicates the presence of different proportion of 3- and 4-coordinated borons in the glass network.

Judd–Ofelt analysis and radiative properties of the Sm3+ centres in Li2B4O7, CaB4O7, and LiCaBO3 glasses

The spectroscopic and luminescence properties of a series Sm-doped Li2B4O7, CaB4O7, and LiCaBO3 borate glasses are investigated using optical absorption, photoluminescence, and decay kinetics techniques as well as Judd–Ofelt (J–O) analysis. Borate glasses of high chemical purity and optical quality, doped with Sm2O3 in amounts of 0.5 and 1.0mol.% were obtained from the corresponding polycrystalline compounds in the air atmosphere using standard glass synthesis technology. The J–O intensity parameters have been calculated using the spectral intensities of the Sm3+ absorption bands. Radiative properties such as transition probabilities, branching ratios, stimulated emission cross-sections, and radiative lifetimes are estimated for 4G5/2→6HJ (J=5/2, 7/2, 9/2, and 11/2) emission transitions of the Sm3+ ions. The luminescence kinetics of the Sm3+ centres are characterised by slightly non exponential decay with lifetime values, which depend on the basic glass composition and Sm impurity concentration. The measured lifetimes were compared with those calculated and quantum efficiencies have been estimated. The obtained high quantum efficiencies of emission transitions (∼70%) and high quantum yields of luminescence (∼14%) of the Sm3+ centres show that the investigated borate glasses belong to perspective luminescent and laser materials.

Optical absorption spectra and energy levels of Er3+ ions in glassy lithium tetraborate matrix

The optical absorption spectra of Er:Li2B4O7 glasses are studied in the range 200–800 nm. The lines corresponding to the direct f-f parity-forbidden intraconfigurational transitions from the ground 4I15/2 state to the levels of the excited 4F9/2, 4S3/2, 2H9/2, 2H11/2, 4F7/2, 4F5/2, 4F3/2, 2H9/2, 4G11/2, 4D3/2, 4D1/2, and 2D3/2 states are found.

Excited state characteristics of the Li2B4O7 and KLiB4O7 glasses activated by Cr3+ ions

The excited state characteristics by means of the excited state absorption (ESA), optical gain and bleaching spectra have been measured for prototype glasses with Li2B4O7 (LBO) and KLiB4O7 (KLBO) compositions activated by Cr3+ ions. The work addressed to search for novel attractive media for broadband lasers and amplifiers, is a completion of detailed spectroscopic evaluation described in earlier papers. One of the examined materials (KLBO), in accordance with optimistic comments given in previous work, reveals a very broad gain spectrum in the near IR, which itself is interesting in view of very few reports on glasses showing optical gain for Cr3+ ions in the low-field local environment. The ESA/gain/bleaching spectra, registered with equipment of improved sensitivity, have been reproduced by calculations, and detailed single configuration coordinate diagram, based on experimental data, has been created for interpretation.

The chromium site in doped glassy lithium tetraborate

Using extended X-ray absorption fine structure (EXAFS) spectroscopy, we find that Cr substitutes primarily in the Li+ site as a dopant in lithium tetraborate Li2B4O7 glasses, in this case 98.4Li2B4O7–1.6Cr2O3 or nominally Li1.98Cr0.025B4O7. This strong preference for a single site is nonetheless accompanied by site distortions and some site disorder, helping explain the optical properties of chromium doped Li2B4O7 glasses. The resulting O coordination shell has a contraction of the Cr–O bond lengths as compared to the Li–O bond lengths. There is also an increase in the O coordination number.

Intensive white light emission from Dy3 +-doped Li2B4O7 glasses

(100−x)Li2B4O7:xDy2O3 (LBO:xDy3+) glasses were developed to be used for white light-emitting-diodes (W-LEDs). The luminescent properties were investigated by excitation and emission spectra. Approximate equal intensity of blue and yellow emissions bands was detected upon excitation from near-ultraviolet (N-UV) to blue light range. Combination of these blue and yellow bands gives rise to intensive white light to the naked eyes. The optimal concentration of Dy2O3 is 0.5mol% under 350nm excitation; the corresponding chromaticity coordinates (0.342, 0.372) in the white region is very near to the standard equal energy white light point (0.333, 0.333). The nature of energy transfer among Dy3+ ions was confirmed by Huang's rule. Simulation results of white light reveal that the color coordinates is insensitive to content and excitation wavelength of the incorporated Dy3+ ions. All results imply that the investigated LBO:xDy3+ glasses is of significance for W-LEDs application.