Metal Oxide Glasses Research Articles

Glass Former Effects on Photoluminescence and Optical Properties of Some Heavy Metal Oxide Glasses Doped with Transition Metal Ions

Heavy metal oxide (PbO and Bi2O3) glasses doped with transition metal (TM) ions (TiO2, V2O5, Cr2O3, and MnO2) and having low content of common glass formers (B2O3, SiO2, or P2O5) were prepared by the conventional melt annealing method. Ultraviolet, visible absorption, and photoluminescence properties of these glasses were measured, and the data were employed to investigate the prepared glassy samples. The optical absorption spectra of TiO2 and V2O5 exhibited three bands centered at about 240, 305, and 380 nm, followed by a broad asymmetrical near-visible band centered at 425–432 nm, while Cr2O3 and MnO2 exhibited an extended visible peak at 517–548 nm. Results showed that the luminescence intensity changed with different transition metal oxides. From the absorption edge data, the values of the optical band gap Eopt and Urbach energy (ΔE) were calculated. The calculated values of the optical energy gap were found to be dependent on the glass composition. The changing values of optical band gap and band tail can be related to the structural changes that are taking place in the glass samples. The variations of the luminescence intensity, values of optical band gap, band tail, and refractive index gave an indication of the potential use of the prepared glasses to design novel optical functional materials with higher optical performance.

Study of structural and spectroscopic behavior of Sm3+ ions in lead–zinc borate glasses containing alkali metal ions

High luminescence behavior of rare earth inorganic glasses have a variety of uses in the industry. In the past few decades, rare earth ions with characteristic photonics applications are being hosted by heavy metal oxide glasses. Among the rare earth ions Sm3+ ion has features which make it apt for high density optical storage. The authors of the paper have experimented to synthesize Sm3+ doped glasses. In this regard a new series of borate glasses doped with 1 mol% Sm3+ ion are developed by using melt-quenching technique. XRD, FTIR, optical absorption, luminescence techniques are used to study the various characteristics of Sm3+ ion in the present glass matrices. The XRD spectra confirms the amorphous nature of glasses. Further, the researchers have used differential thermal analysis to study the glass transition temperature. The structural groups in the prepared glasses are studied using Fourier transform infrared spectra. From the measurement of its optical absorption, three phenomenological Judd–Ofelt intensity parameters (Ω2, Ω4 and Ω6) have been computed. Based on these Judd–Ofelt intensity parameters, radiative properties such as radiative probabilities (Arad), branching ratios (β), and radiative life time (τR) are calculated. The excitation spectra of Sm3+ doped lithium heavy metal borate glass matrix is recorded under the emission wavelength of 600 nm. The emission spectra are recorded under 404 nm excitation wavelength. From various emission transitions, 4G5/2 → 6H7/2 and 4G5/2 → 6H9/2 bands could be of interest for various applications. The decay profiles of 4G5/2 level exhibit single exponential nature in all the prepared glass matrices. The potassium glass matrix exhibits higher quantum efficiency than the other glass matrices. Finally, by going through these several spectroscopic characterizations, it is concluded that the prepared Sm3+ doped lead–zinc borate glasses might be useful for visible light applications.

Antimony oxide based glasses, novel laser materials

Glasses based on Sb2O3 make one of the major classes of heavy metal oxide glasses. This paper concerns two antimonite glasses, 88Sb2O3-10Na2O-2Bi2O3 (SNB2) and 60Sb2O3-20WO3-19Na2O-1Bi2O3 (SWNB1), doped with 0.25 mol% Er2O3. Bulk samples have been prepared and their absorption and fluorescence spectra have been recorded. Differential scanning calorimeter (DSC) measurements emphasize a thermal stability range ΔT > 100 °C that expresses a good stability against devitrification. Both FTIR and Raman spectra provide information on the structural organization of the glasses. The maximum phonon energies are 700 cm−1 and 920 cm−1 for SNB2 and SWNB1 glasses, respectively. The spectroscopic analysis of the absorption and emission properties of the Er3+ ions in the SNB2 and SWNB1 glasses has been performed. The Judd-Ofelt theory has been applied to interpret the local environment of the Er3+ ion site and covalency of the ErO bond, but also to determine the radiative lifetime (τr) for 4I13/2 → 4I15/2 emission transition. The emission cross-sections for the 4I13/2 → 4I15/2 transition (1528 nm) were calculated using McCumber and Füchtbauer-Ladenburg theories. We discuss the potential application of these glasses.

High numerical aperture large-core photonic crystal fiber for a broadband infrared transmission

In this paper we present a large mode area photonic crystal fiber made of the heavy metal oxide glass CS-740, dedicated for a broadband light guidance in the visible, near- and mid-infrared regions of wavelengths from 0.4 to 4.7μm. The fiber is effectively multi-mode in the considered wavelength range. It is composed of a ring of air-holes surrounding the core, with a high linear filling factor of 0.97. The fiber was made using a standard stack-and-draw technique. Each hole has a size of approx. 2.5×3.0μm and diameter of core is 80μm. Fiber attenuation is below 3dB/m in the 0.9–1.7μm wavelength range, while at 4.4μm (mid-IR) it is approx. 5dB/cm. Bending loss at the 1.55μm wavelength is 0.45dB per loop of 8mm radius. Fiber numerical aperture is 0.53 at 1.55μm. The effective mode area of the fundamental mode is approx. 2400μm2 in the wavelength range of 0.8–1.7μm. We present a proof-of-concept demonstration that our large core photonic crystal fiber is able to efficiently collect light directly from a mid-IR quantum cascade laser without use of additional optics and can be used for pigtailing mid-IR sources and detectors.

Temperature sensitivity of chromatic dispersion in nonlinear silica and heavy metal oxide glass photonic crystal fibers

In this paper we report on the examination of the temperature influence of the effective refractive index and on the dispersion characteristics in air-hole lattice photonic crystal fibers. We use an original method to measure the temperature influence on chromatic dispersion in an optical fiber, where both the thermal expansion of the fiber and its effective group refractive index are taken into account. We present the experimental and modeling results of dispersion characteristics for two types of non-linear fibers, a silica glass fiber and a soft glass fiber in the temperature range from 20°C to 420°C. We measured the zero dispersion wavelength shift of + 0.020 nm/°C for the fused silica fiber and + 0.045 nm/°C for the heavy metal oxide soft glass fiber. Experimental results are in agreement with numerical modeling. Finally, the influence of the temperature-induced change of the dispersion profile on nonlinear performance of the studied fiber structures is investigated numerically. Notable change of parametric gain maxima locations is observed even for small changes of the zero dispersion wavelength in relation to the pump laser wavelength in a four-wave mixing fiber-based wavelength conversion scenario.

Determination of effective atomic number and electron density of heavy metal oxide glasses

ABSTRACTThe effective atomic number (Zeff) and effective electron density (Neff) of eight heavy metal oxide (HMO) glasses have been determined using the Monte Carlo simulation code MCNP for the energy range of 10 keV–10 MeV. The interpolation method was employed to extract Zeff and Neff values from the simulation and that calculated with the help of XCOM program. Comparisons are also made with predictions from the Auto-Zeff software in the same energy region. Wherever possible, the simulated values of Zeff and Neff are compared with experimental data. In general, a very good agreement was noticed. It was found that the Zeff and Neff vary with photon energy and do not have extended intermediate regions where Compton scattering is truly dominating; only dips slightly above ∼1.5 MeV were recorded. Zeff and Neff are found to increase with PbO and Bi2O3 contents. It was found that the Zeff value rather than the Neff value is a better indicator for PbO and/or Bi2O3 contents.

GLASSY MATERIALS AND LIGHT: PART 1

2015 is the Year of Light, according to UNESCO. Chemistry has a close relationship with light and one of the materials that allows such synergy is glass. Depending on the chemical composition of the glass, it is possible to achieve technological applications for the whole range of wavelengths extending from the region of the microwave to gamma rays. This diversity of applications opens a large range of research where chemistry, as a central science, overlaps the fields of physics, engineering, medicine, etc., generating a huge amount of knowledge and technological products used for humanity. This review article aimed at discussing some families of glasses, illustrating some applications. Due to the extension of the theme, and all points raised, we thought it would be good to divide the article into two parts. In the first part we focus on the properties of heavy metal oxide glasses, fluoride glasses and chalcogenide glasses. In the second part we emphasize the properties of glassy thin films prepared by sol-gel methodology and some applications, of both glasses as the films in photonics, and more attention was given to the nonlinear properties and uses of photonic fibers.

Novel method for metal-oxide glass composite fabrication for use in thermoelectric devices

A novel method for thermoelectric materials fabrication using a reduction of oxide precursors in hydrogen was reported. On the example of Bi–Sb, Bi–Sb–Te and Te–Ag–Ge–Sb compounds it was shown that this simple and easy method is suitable for fabrication of two-, three- and even multicomponent thermoelectric materials. It allows controlling a composition, microstructure and even type a of electrical charge carriers. As a result of reduction of oxide precursors a layered structure with an average thickness of layers equal tens of nanometers was formed. At the near-room temperature the best material with a figure of merit (ZT) close to 0.4 was Bi0.8Sb1.2Te3Ox reduced at 340°C for 10h. At 350°C a value of ZT=0.8 was reached by the (GeTe)0.85(AgSbTe2)0.15 (TAGS85) sample reduced twice at 400°C for 10h.

Photoluminescence and semiconducting behavior of Fe, Co, Ni and Cu implanted in heavy metal oxide glasses

Transition metal ions (0.5wt%) of Fe2O3, CoO, NiO or CuO doped heavy metal oxide glasses having chemical composition of 60PbO·20Bi2O3·20MxOy mol% (where MxOy=B2O3 or SiO2 or P2O5) were prepared by conventional melt annealing method. Combined optical and photoluminescence properties have been measured and employed to evaluate the prepared glassy samples. From the absorption edge data, the values of the optical band gap Eopt, Urbach energy (ΔE) and refractive index were calculated to estimate semiconducting behavior. Photoluminescence and values of the optical energy gap were found to be dependent on the glass composition. The variations of the photoluminescence intensity, values of optical band gap, Urbach energy and refractive index gave an indication to use the prepared glasses for design of novel functional optical materials with higher optical performance.

Integration Between Optical and Structural Behavior of Heavy Metal Oxide Glasses Doped with Multiple Glass Formers

Heavy metal oxide glasses (composition 60 PbO, 20 Bi2O3 mol%) and containing 20 mol% conventional glass formers SiO2, B2O3, and P2O5 were prepared. Combined optical and Fourier transform infrared absorption spectra were measured for the prepared glasses to justify the role of glass formers in the optical spectra together with the network structural groups in such glasses. Also, the density and molar volume values were calculated to obtain some insight on the compactness and arrangement in the network. Optical measurements have been used to determine the optical band gap (Eg), Urbach energy (ΔE) and the refractive index (n). Optical spectra of all the samples reveal strong UV absorption which is related to the presence of unavoidable trace iron impurities (Fe 3+ ions) contaminated within the raw materials which were used for the preparation of the studied glasses. Additional near visible bands are observed in all prepared glasses due to characteristic absorption of Pb 2+ and Bi 3+ ions. Furthermore, The variations of the luminescence intensity, values of the optical band gap, band tail, and refractive index can be understood and related in terms of the structural changes that take place in the glass samples. The infrared absorption spectra of the prepared glasses show characteristic absorption bands related to the borate or silicate or phosphate network (BO3, BO4, SiO4, PO4 groups) together with vibrational modes due to Bi-O and Pb-O groups.

Probing Metal-Bridging Oxygen and Configurational Disorder in Amorphous Lead Silicates: Insights from 17O Solid-State Nuclear Magnetic Resonance

The detailed degree of mixing between framework Si and metal cations and the nature of oxygen that only links metal cations (metal-bridging oxygen) in archetypal metal oxide glasses have been among the unsolved problems in physical chemistry. Binary lead silicate (PbO-SiO2) glass is an ideal model system for exploring the extent of cation disorder and metal-bridging oxygen because of its peculiar glass-forming ability at high PbO concentration. Here we report the first high-resolution 17O solid-state NMR spectra for binary lead silicate glasses with varying composition (near that of orthosilicate, i.e., Pb/Si = 2), where peaks due to metal-bridging oxygen (Pb-O-Pb), as well as Pb-O-Si and Si-O-Si are clearly resolved. The spectra also reveals that the metal-bridging oxygen possesses a greater topological disorder due to structural complexity in Pb coordination environments. Together with a statistical thermodynamic model of oxygen speciation proposed to describe mixing behavior in oxide glasses with any o...

Radiation shielding competence of silicate and borate heavy metal oxide glasses: Comparative study

Gamma-ray shielding competence of silicate and borate heavy metal oxide glasses has been investigated using linear attenuation coefficients, effective atomic numbers and exposure buildup factors (EBF). The gamma-ray EBF were computed using the Geometric Progression (G-P) fitting method for photon energies from 0.015 to 15MeV, and for penetration depths up to 40 mean free paths (mfps). The macroscopic effective removal cross-section for fast neutron has been calculated for energy range from 2 to 12MeV. It is found that bismuth silicate glass has superior shielding properties and is suitable for replacement of lead glasses. The present investigation is very useful for gamma-ray and neutron shielding and design for lead-free shielding glass in radiological engineering.

Contact resistivity decrease at a metal/semiconductor interface by a solid-to-liquid phase transitional metallo-organic silver.

We present a new approach to ensure the low contact resistivity of a silver paste at a metal/semiconductor interface over a broad range of peak firing temperatures by using a solid-to-liquid phase transitional metallo-organic silver, that is, silver neodecanoate. Silver nanoclusters, thermally derived from silver neodecanoate, are readily dissolved into the melt of metal oxide glass frit even at low temperatures, at which point the molten metal oxide glass frit lacks the dissociation capability of bulk silver into Ag(+) ions. In the presence of O(2-) ions in the melt of metal oxide glass frit, the redox reaction from Ag(+) to Ag(0) augments the noble-metal-assisted etching capability to remove the passivation layer of silicon nitride. Moreover, during the cooling stage, the nucleated silver atoms enrich the content of silver nanocolloids in the solidified metal oxide glass layer. The resulting contact resistivity of silver paste with silver neodecanoate at the metal/semiconductor interface thus remains low-between 4.12 and 16.08 mΩ cm(2)-whereas without silver neodecanoate, the paste exhibits a contact resistivity between 2.61 and 72.38 mΩ cm(2) in the range of peak firing temperatures from 750 to 810 °C. The advantage of using silver neodecanoate in silver paste becomes evident in that contact resistivity remains low over the broad range of peak firing temperatures, thus providing greater flexibility with respect to the firing temperature required in silicon solar cell applications.

Characterization of new Sb2O3-based multicomponent heavy metal oxide glasses

New Sb2O3-based multicomponent heavy metal oxide glasses in the Sb2O3–Na2O–WO3–PbO system were prepared using a conventional melt-quenching technique. Glass formation behavior of these glasses and their thermal, physical and structural properties were investigated using X-ray diffraction (XRD), scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM/EDS), differential scanning calorimetry (DSC), UV–Vis–NIR spectroscopy and Fourier transform infrared (FTIR) spectroscopy analyses according to the increasing PbO concentration by keeping the Sb2O3/WO3 ratio constant. Thermal analysis of the glasses were realized in terms of glass transition temperature (Tg), crystallization temperature (Tc/Tp), glass stability against crystallization (ΔT), activation energy of the glass transition reaction (Eg) and fragility parameter (m). Density (ρ), molar volume (VM), oxygen molar volume (VO), oxygen packing density (OPD), refractive index, band gap energy (Eg), average cross-link density (nc‾), number of bonds per unit volume (nb) and Poisson’s ratio (μcal) values were calculated for the interpretation of physical and structural properties of the glasses. FTIR spectra of the glasses were evaluated in terms of structural transformations on the glass network.

Two Octaves Supercontinuum Generation in Lead-Bismuth Glass Based Photonic Crystal Fiber.

In this paper we report a two octave spanning supercontinuum generation in a bandwidth of 700–3000 nm in a single-mode photonic crystal fiber made of lead-bismuth-gallate glass. To our knowledge this is the broadest supercontinuum reported in heavy metal oxide glass based fibers. The fiber was fabricated using an in-house synthesized glass with optimized nonlinear, rheological and transmission properties in the range of 500–4800 nm. The photonic cladding consists of 8 rings of air holes. The fiber has a zero dispersion wavelength (ZDW) at 1460 nm. Its dispersion is determined mainly by the first ring of holes in the cladding with a relative hole size of 0.73. Relative hole size of the remaining seven rings is 0.54, which allows single mode performance of the fiber in the infrared range and reduces attenuation of the fundamental mode. The fiber is pumped into anomalous dispersion with 150 fs pulses at 1540 nm. Observed spectrum of 700–3000 nm was generated in 2 cm of fiber with pulse energy below 4 nJ. A flatness of 5 dB was observed in 950–2500 nm range.

Conductive and transparent multilayer films for low-temperature TiO2/Ag/SiO2 electrodes by E-beam evaporation with IAD

Conductive and transparent multilayer thin films consisting of three alternating layers (TiO2/Ag/SiO2, TAS) have been fabricated for applications as transparent conducting oxides. Metal oxide and metal layers were prepared by electron-beam evaporation with ion-assisted deposition, and the optical and electrical properties of the resulting films as well as their energy bounding characteristics and microstructures were carefully investigated. The optical properties of the obtained TAS material were compared with those of well-known transparent metal oxide glasses such as ZnO/Ag/ZnO, TiO2/Ag/TiO2, ZnO/Cu/ZnO, and ZnO/Al/ZnO. The weathering resistance of the TAS film was improved by using a protective SiO2 film as the uppermost layer. The transmittance spectra and sheet resistance of the material were carefully measured and analyzed as a function of the layer thickness. By properly adjusting the thickness of the metal and dielectric films, a low sheet resistance of 6.5 ohm/sq and a high average transmittance of over 89% in the 400 to 700 nm wavelength regions were achieved. We found that the Ag layer played a significant role in determining the optical and electrical properties of this film.

Designing heavy metal oxide glasses with threshold properties from network rigidity

Here, we show that a new class of glasses composed of heavy metal oxides involving transition metals (V2O5-TeO2) can surprisingly be designed from very basic tools using topology and rigidity of their underlying molecular networks. When investigated as a function of composition, such glasses display abrupt changes in network packing and enthalpy of relaxation at Tg, underscoring presence of flexible to rigid elastic phase transitions. We find that these elastic phases are fully consistent with polaronic nature of electronic conductivity at high V2O5 content. Such observations have new implications for designing electronic glasses which differ from the traditional amorphous electrolytes having only mobile ions as charge carriers.

Ultrafast third-order optical nonlinearities of heavy metal oxide glasses containing gold nanoparticles

This work reports on the third-order nonlinear properties and the response time of GeO2–Bi2O3 glass, as well as the effect of gold nanoparticles on these properties. The nonlinear refractive index spectrum and the nonlinear absorption coefficient were determined by the Z-scan technique, and the response time was obtained through Kerr gate measurements, using femtosecond pulses. The results show that the presence of gold nanoparticles causes a saturable absorption effect that is overcome by the two-photon absorption process at higher light intensities, for wavelengths within the plasmon band. We measured a constant value for the nonlinear refractive index (n2) for the visible and infrared regions, which was not affected by the presence of gold nanoparticles in the sample. However, the n2 value is one order of magnitude higher than the one for fused silica and 1.5times better than PGO (PbO–GeO2) glasses. In addition, the response time of the induced birefringence for the samples with and without gold nanoparticles is faster than the pulse duration (220fs), indicating an ultra-fast electronic process.

Optical characterization of heavy metal non-conventional binary PbO–ZnO glasses

Non-conventional heavy metal oxide glasses of the system (100−x) PbO–xZnO in the composition range 5–40 mol% of ZnO have been prepared by melt-quenching technique. X-ray diffraction, UV–visible, and Fourier transform infrared (FTIR) absorption spectroscopy techniques were applied for the characterization of prepared glasses. From the absorption edge studies, the values of the optical band gap Eopt and Urbach energy (∆E) have been evaluated. From the experimental results, values of the optical energy gap are calculated and found to be dependent on the glass composition. FTIR spectra of the glasses reveal vibrational modes characteristic to combined presence of tetrahedral PbO4 and ZnO4 units in their specific different wavenumbers.

Luminescent GeO2–Pb–Bi2O3 glasses co-doped with Tb3+1 and Eu3+: Excitation energy transfer and color chromaticity

Heavy metal oxide glass of the type GeO2–PbO–Bi2O3 was applied as a matrix for luminescent materials co-doped with Tb3+ and Eu3+ ions of different molar ratio. The undoped glass matrix with the composition 80GeO2–19PbO–1Bi2O3 was characterized by XRD and DSC techniques. Its structure was studied by FTIR spectroscopy. The FTIR spectra suggested that GeO4, GeO6, BiO3, BiO6, PbO3 and PbO4 structural units are present in the glass. In the case of the 79GeO2–19PbO–Bi2O3–xEu2O3–(1−x)Tb2O3 luminescent glasses, reflection, luminescence and excitation spectra were recorded as well as time resolved luminescence technique was used. Two luminescence effects were analyzed, viz. cross relaxation and Tb3+→Eu3+ energy transfer.