Lead Borosilicate Glass Research Articles

Electrical conductivity and glass transition temperature (Tg) measurements on some selected glasses used for nuclear waste immobilization

Borosilicate glass, alumino-borosilicate glass, barium borosilicate glass and lead borosilicate glasses were prepared by melting the glass forming reagents of the respective glass compositions in air ambience. The glasses were characterised by powder X-ray diffractometry. The electrical conductivity of these four glasses was measured by impedance measurements. The conductivities were attributed mainly due to conduction of Na+ ion in the glass network and were in the range of 9.92×10−9–1.74×10−3Ω−1cm−1 at 400–900K. The activation energies of conduction for these glasses were found to be 0.96±0.01eV for borosilicate glass, 1.19±0.01eV for alumino-borosilicate glass, 1.19±0.01eV for barium borosilicate glass and 1.24±0.01eV for lead borosilicate glass. Diffusion coefficient of the conducting species (Na+-ion) was calculated from the conductivity values using Nernst Einstein equation, and the values were in the range of 5.28±0.03×10−13–1.78±0.01×10−8cm2s−1. Glass transition temperatures of these glasses were measured by differential scanning calorimetry as well as by dilatometric methods. Tg measured by differential scanning calorimetry were found to be 813±4, 820±4, 785±4 and 749±4K for borosilicate glass, alumino-borosilicate glass, barium borosilicate glass and lead borosilicate glass respectively, and Tg measured by dilatometric method was 799±5, 818±5, 781±5 and 742±5K for borosilicate glass, alumina-borosilicate glass, barium borosilicate glass and lead borosilicate glass respectively.

Effect of Dy3+ ions concentration on optical properties of lead borosilicate glasses for white light emission

Lead borosilicate (LBS) glasses doped with different concentrations of Dy3+ ions (0.1, 0.5, 1.0 and 2.0 mol%) were synthesized by the conventional melt quenching method. The prepared glasses were characterized through X-ray diffraction (XRD), optical absorption and photoluminescence spectra. The glassy nature of LBS host glass has been confirmed from XRD analysis and the Judd–Ofelt (JO) intensity parameters (Ωλ, λ = 2, 4 and 6) have been calculated from the intensities absorption bands. The evaluated parameters are then used to calculate radiative properties such as radiative transition probabilities (AR), total transition probability (AT), radiative lifetime (τR) and branching ratios (βR) for the excited 4F9/2 level of Dy3+ ions. From the emission spectra, the effective band widths (Δλeff), stimulated emission cross-sections (σ(λp)), yellow to blue (Y/B) intensity ratios, experimental lifetimes (τexp) of 4F9/2 metastable state and the chromaticity color coordinates for white light emission have been determined and discussed.

Current Transport Through Lead–Borosilicate Interfacial Glass Layers at the Screen–Printed Silver-Silicon Front Contact

During the firing of screen-printed silver contacts in industrial crystalline silicon solar cells, an interfacial glass layer is formed between the silver bulk contact and the silicon substrate. By means of numerical modeling, we investigate conduction mechanisms across the interfacial glass layer, which consists of lead–borosilicate glass enclosing silver colloids. As there is a considerable lack of parameters for the interfacial glass layer, we revisit properties of similar materials such as as-grown crystalline and polycrystalline lead monoxide. We revise characteristics of applications that use similar glasses, such as photodetectors, thick-film transistors, and surface passivation. We propose that current transport via the interfacial glass is similar to the one in thick-film resistors based on ruthenium-doped lead–borosilicate glass. Device simulations are performed using direct tunneling, trap-assisted tunneling, and a conducting insulator model for current transport across the interfacial glass layer. The tunneling mechanisms are only effective for thin interfacial glass layers up to 2 nm. A combination of direct tunneling and the conducting insulator modeling is well suited to model interfacial glass layers between 0.5 and 1000 nm. Applications to specific contact resistance measurements show that the resistivity of the interfacial glass is in the range of thick-film resistors of similar lead monoxide content.

Estudo das propriedades ópticas de vidros borosilicatos dopados com íons de Itérbio em função da concentração

Rare Earth elements have been studied for different scientific areas due to its excellent spectroscopic and magnetic properties with possible application for construction of different optical and electric devices (MARTINS, 2005; LOURENCO et al., 2011). In this work, it is studied the optical properties of Ytterbium (Yb 3+ ) ions embedded in a lead-borosilicate glass matrix synthesized by the melting method, using the optical absorption and photoluminescence techniques. The Yb 3+ ions were chosen to dope the glass matrix because it has an energy level scheme more simplified compared with other Rare-Earth ions, with only two energy levels, making it very attractive for the construction of high efficiency optical devices. Increasing the annealing temperature as well as the ion concentration in the matrix leads to a shift of the optical band gap of the matrix to higher energies. We believe that this shift (blue-shift) can be associated with the nanocrystallization process of the glass matrix SBP (SiO 2 , B 2 O 3 , PbO 2 ). The reduction of radiative lifetime with increasing ion concentration in matrix was studied using the Stokowski empirical relation, in which, it studies processes of energy transfer as a function of Rare-Earth concentration.

Mechanism underlying the beneficial effect of forming gas annealing on screen-printed Ag contacts of crystalline Si solar cells

Forming gas annealing (FGA) has been known to be beneficial for improving the contact resistance of crystalline Si (c-Si) solar cells containing overfired front-side Ag contacts. This study examines the microstructural changes responsible for the beneficial effect of FGA through the use of ultrahigh-resolution scanning electron microscopy. The FGA process at 400°C under N2+10% H2 led to the formation of a layer of fine (<300nm) Ag particles on the glass surface of the interfacial pores, which were connected to the open channels in the porously sintered Ag bulk. Aside from the pore surfaces, FGA had little influence on the contact microstructure, and there was no noticeable formation of Ag or other metallic particles within the interfacial glass layer. The present results demonstrate that the Ag+ ions dissolved into the lead borosilicate glass during the firing process, and subsequently diffused out only to be reduced in the vicinity of the pore surfaces during FGA. This result suggests that the permeation rate of hydrogen into the lead borosilicate glass should be negligible, compared to the out-diffusion rate of the Ag+ ions during FGA. Furthermore, the conductivity measurements indicated that the pore surfaces that were decorated with a dense layer of fine Ag particles after FGA could act as an additional path for current transport across the contact interface, thereby lowering the contact resistance.

Influence of oxygen on Ag ionization in molten lead borosilicate glass during screen-printed Ag contact formation for Si solar cells

In order to gain further insight into the formation mechanism of fire-through Ag contacts of Si solar cells, the ionization of Ag during the dissolution of Ag powder into a lead borosilicate glass melt was electrochemically investigated at 800°C under various ambient conditions with different oxygen partial pressures (PO2). Voltammetric analyses of the Ag-free and Ag-containing glass melts confirmed that some of the Ag powder dissolved into the molten glass as Ag+ ions through interaction of the powder with oxygen in the ambient atmosphere. The concentration of Ag+ in the molten glass significantly increased with increasing PO2. The dependence of the Ag+ solubility in the molten glass on PO2 was estimated from chronoamperometric measurements for a series of glass melts containing different amounts of Ag powder. The chronoamperometry results clearly demonstrated that the solubility limit of Ag+ in the molten glass at 800°C also increased significantly with increasing PO2. The present results strongly support the mechanism proposed recently for fire-through Ag contact formation in which Ag+ ions dissolved in the molten glass play a crucial role. The present study also suggests that the reaction kinetics during the fire-through Ag contact formation is effectively controlled by adjusting PO2 in the ambient firing conditions as well as by modifying the glass chemistry to alter the solubility of Ag+ ions.

Magnetic losses in metal nanoparticle-insulator nanocomposites

Metal nanoparticle-insulator nanocomposites were synthesized and characterized for their magnetic loss and frequency-stability to understand the role of metal particle size and oxide passivation. Cobalt nanocomposites were synthesized with different matrices such as lead-borosilicate glass, silica and polymers, and fabricated into toroids for characterizing their microstructure and magnetic properties. X-ray Diffraction and Transmission Electron Miscroscopy were used to characterize the microstructure while Vibration Sample Magnetometry and impedance spectroscopy were used to obtain saturation magnetization, coercivity, permeability and magnetic loss. Nanocomposites with particles in the size range of 40–90 nm showed poor frequency stability and high loss beyond 200 MHz while finer particles (25–40 nm) resulted in stable properties beyond 500 MHz. The high coercivity and FMR broadening with oxide-passivated nanoparticle composites, however, degraded the magnetic losses at 500 MHz even with finer particles. The role of particle size and surface effects in suppressing the permeability and enhancing the frequency-stability is discussed.

Transport properties of microwave sintered pure and glass added MgCuZn ferrites

Abstract A series of pure stoichiometric and 1 wt% lead borosilicate (PBS) glass added MgCuZn ferrite with the general formula Mg 0.5 Cu x Zn 0.5− x Fe 2 O 4 with x = 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3 were synthesized by microwave sintering technique. Single phase spinel structure is exhibited by the XRD patterns of these ferrites. DC and AC conductivity were investigated as a function of composition, temperature and frequency. DC conductivities were also estimated using the impedance spectroscopy analysis of Cole–Cole plots. The DC conductivities thus obtained are in good agreement with the experimental results. All the investigated samples exhibited two regions of conductivity one in the low temperature and the second in the high temperature region. It is observed that PBS glass added samples have lower conductivities than pure samples. Due to their lower conductivities and sintering temperatures the 1 wt% PBS glass added samples are suitable for multilayer chip inductor (MLCI) and high definition TV deflection yoke material application.

Efficient energy transfer mediated by intrinsic SiO2 nanocrystals in Eu+3-doped lead borosilicate glasses

Lead borosilicate glass (SiO2–B2O3–PbO2) doped with different Eu3+ ion concentrations have been synthesized by fusion method and characterized through optical absorption, photoluminescence (PL) and time-resolved PL spectra in the temperature range from 15 to 300 K. The PL spectra show characteristic ions Eu3+ transitions followed by a red emission at 695 nm and a green emission at 550 nm. The red and green emissions were associated with a non-bridging oxygen hole center (NBOHC) and OH groups stabilized on the SiO2 nanocrystal surface, respectively. Atomic Force Microscopy images confirm a precipitated crystalline phase with size of 21 nm in the glass matrix. Inhibition of the intrinsic nano-crystallization process of the SBP glass template has been observed as Eu3+ ions concentration increases. As sample temperature increases, an efficient energy transfer process from SiO2 nanocrystal surface states toward Eu3+ states takes place. This leads to a strong increase in the PL emission intensity of Eu3+ states followed by a decreasing PL peak intensity of the surface states. The energy transfer process leads also to an abnormal average lifetime of SBP:Eu3+ luminescent states with increasing temperature.

Release of uranium from candidate wasteforms

AbstractLarge volumes of depleted natural and low-enriched uranium exist in the UK waste inventory. This work reports on initial investigations of the leaching performance of candidate glass and cement encapsulation matrices containing UO3 powder as well as that of uranium oxide powders. The surface areas of UO3 powder and the monolith samples of UO3 conditioned in the glass and cement matrices were very different making leaching comparisons difficult. The results showed that for both types of monolith conditioned samples a steady increase of uranium concentration in solution with time was generally not observed. The wt.% of uranium leached from UO3 conditioned in the lead borosilicate glass wasteform was approximately five orders of magnitude less than that leached from UO3 powder. Similarly, the quantities of uranium leached from UO3 conditioned in composite cement made with ordinary Portland cement, and from magnesium phosphate cement, were approximately four and three orders of magnitude, respectively, less than that leached from UO3 powder. The performance of a mixed oxide borosilicate glass wasteform was only slightly better than that of UO3 powder. This work shows that wasteforms based on encapsulation in lead borosilicate glass and cement matrices have the greatest potential for further development.

Role of aluminium oxide in the structure of heavy metal oxide borosilicate glasses

AbstractLead borosilicate and bismuth borosilicate glasses with and without aluminium oxide of varying compositions were prepared by conventional melt‐quench method. Raman spectroscopy was used to analyze the influence of Al2O3 incorporation in the heavy metal oxide borosilicate glass network. The compositions of glasses were chosen in a way that Al2O3 is added at expenses of PbO and Bi2O3 in lead borosilicate and bismuth borosilicate glasses, respectively.

Investigation into the charge-carrier generation processes in MIS structures with lead borosilicate glass-based dielectrics

The generation properties of the silicon — lead-borosilicate glass interface are studied by the method of pulsed MIS capacitor. It was shown that surface generation current nomonotonicly depends on temperature. This nomonotonic dependence may be the result of tunnel and tunnel activated current from traps states in lead-borosilicate glasses localized close to the silicon-glass interface which contributes to the total surface generation current and becomes dominant as the temperature is lowered.

Microstructure and microwave dielectric properties of lead borosilicate glass ceramics with Al2O3

The effects of Al2O3 addition on both the sintering behavior and microwave dielectric properties of PbO-B2O3-SiO2 glass ceramics were investigated by Fourier transform infrared spectroscope (FTIR), differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that with the increase of Al2O3 content the bands assigned to [SiO4] nearly disappear. Aluminum replaces silicon in the glass network, which is helpful for the formation of boron-oxygen rings. The increase of the transition temperature Tg and softening temperature Tf of PbO-B2O3-SiO2 glass ceramics leads to the increase of liquid phase precipitation temperature and promotes the structure stability in the glasses, and consequently contributes to the decreasing trend of crystallization. Densification and dielectric constants increase with the increase of Al2O3 content, but the dielectric loss is worsened. By contrast, the 3% (mass fraction) Al2O3-doped glass ceramics sintered at 725 °C have better properties of density ρ=2.72 g/cm3, dielectric constant ɛr=6.78, dielectric loss tan δ=2.6×10−3 (measured at 9.8 GHz), which suggest that the glass ceramics can be applied in multilayer microwave devices requiring low sintering temperatures.

Dependence of the surface generation velocity at silicon-(lead borosilicate) glass interface on conditions of nonequilibrium depletion region formation

The generation characteristics of silicon-(lead borosilicate) glass interface have been studied by the method of isothermal capacitance transient spectroscopy in the metal-insulator-semiconductor (MIS) structure. It is established that the effective surface generation velocity depends on the amplitude of the inverting voltage pulse that drives the MIS structure out of the equilibrium state. The observed dependence may be caused by the injection of charge carriers through the silicon-glass interface followed by their localization on traps in the region of glass near the interface.

Effect of pressure on the electric properties of passivating coatings based on lead borosilicate glasses

The effect of pressure on the electric properties of dielectric PbO-SiO2-B2O3-Al2O3-Ta2O5 coatings has been studied. The dependence of the parameters of the coatings on the value of the uniform compression has been found.

Low-firing thick-film piezoresistive sensors for medical instruments

In this work, a low-firing thick-film materials system allowing fabrication of piezoresistive sensors on surgical alloys is presented in detail, with application to a force-sensing surgical instrument. The system comprises a series of individual thick-film dielectric, conductor, resistive and overglaze compositions based on a lead borosilicate glass matrix. The moderate achieved firing temperature, around 625°C, greatly increases compatibility with metallic substrates, allowing the use of high-strength medical alloys with low thermal degradation. Specific fillers for the dielectric layers increase adhesion on steel substrates and allow thermal matching to austenitic and ferritic/martensitic steels, as well as titanium alloys, and preliminary work demonstrating reactive stabilisation of the dielectric layer to achieve an even wider process window is also shown. Finally, the functionality of this materials system is successfully demonstrated here by implementing it into a previously developed ligament-balancing force sensor for total knee arthroplasty (TKA) [1].

Load dependence of densification in glass during Vickers indentation test

The load dependence of densification during a Vickers indentation test was investigated for three commercial glass compositions, soda-lime silicate glass, aluminoborosilicate glass, and lead borosilicate glass, each of which exhibits markedl yd ifferent susceptibility to crack initiation. The contribution of densification to the total deformation due to indentation was evaluated as the rati oo f the depths o fi ndentation before and after heat treatment measured with an atomic force microscope (AFM). For the soda-lime silicate and aluminoborosilicate glasses, the contribution of densification decreases with increasing applied load, but the rate of the decrease is less for the alumonoborosilicate glass than for the soda-lime silicate glass. For the lead borosilicate glass, the contribution of densification is low throughout the range o fl oads investigated. The residual stress can be estimated from the contribution of densification, and the variation o fl oad dependence of the residual stress is considered to result i na large difference in the crack initiation load among the glasses.

Eu3+ photoluminescence enhancement due to thermal energy transfer in Eu2O3-doped SiO2–B2O3–PbO2 glasses system

In this work, Eu3+-doped lead borosilicate glasses (SiO2–B2O3–PbO2) synthesized by fusion method had their optical properties investigated as a function of temperature. Atomic Force Microscopy images obtained for a glass matrix annealed at 350 and 500°C show a precipitated crystalline phase with sizes 11 and 21nm, respectively. Besides, as the temperature increases from 350 to 300K a strong Eu3+ photoluminescence (PL) enhancement takes place. This anomalous feature is attributed to the thermally activated carrier transfer process from nanocrystals and charged intrinsic defects states to Eu3+ energy levels. In addition, the PL peaks in this temperature range were assigned to the Eu3+ transitions 5D0→7F2, at 612nm, 5D0→7F1, at 595nm, and 5D0→7F0, at 585nm. It was also observed that the 5D0→7F3 and 5D0→7F4 PL bands at 655 and 700nm, respectively, show a continuous decrease in intensity as the temperature increases.

ChemInform Abstract: Decomposition of Ruthenium Oxides in Lead Borosilicate Glass.

Behaviors of apparent phase changes of Ru-containing oxides in lead borosilicate glass at high temperature have been investigated using X-ray diffraction and transmission electron microscopy in application to thick-film resistors. During firing of thick films containing Ru oxide powder and lead borosilicate glass frits, apparent phase changes of Ru oxides have been found to occur both ways between ruthenium dioxide and lead ruthenate pyrochlore via decomposition of one phase in glass and subsequent formation of the other. The formation of pyrochlore occurs in a lead-rich form, Pb 2 (Ru 2-x Pb x )O 6.5 , whereas the formation of RuO 2 is characterized by a platelike morphology instead of initial globular morphology. A general tendency is observed that RuO 2 is stable in low-PbO glass compositions and at high temperatures, while Pb 2 (Ru 2-x Pb x )O 6.5 is stable in high-PbO glass compositions and at low temperatures, with the implication that the stability of these phases is dictated by the chemical activity of PbO in the glass melt.

Optical study of lead borosilicate glasses

Glasses with compositions xPbO– RNa 2B 4O 7–(100− R− x)CAS (0.49CaO, 0.21Al 2O 3, 0.3SiO 2) with 0≤ x≤50 and 50≤ R≤75 mol% have been prepared using the normal melt quenching technique. The optical transmittance and reflectance spectrum of the glasses have been recorded in the wavelength range 300–1100 nm. The values of the optical band gap E g o p t for indirect transition and refractive index have been determined for different compositions of the amorphous glass. The average electronic polarizability of the oxide ion α o 2 − and the optical basicity have been estimated from the values of calculated refractive indices. The compositional dependence of the different physical parameters such as the density, the optical band gap, the refractive index, the average electronic polarizability of the oxide ion and the optical basicity on PbO content have been analyzed and discussed.