Lead Borosilicate Glass Research Articles

Excitation and Emission Profiles of Cm(III) and Cm(IV) in Neat Samples and Lead Borosilicate Glasses

AbstractWe have been investigating the spectroscopy of actinides in materials having relevance to nuclear waste management. Discussed here are the excitation and emission profiles of curium in high temperature borosilicate glasses, and pure halide compounds. Probing the local coordination environment of Cm(III) in these matrices has been one of the goals of this study. Comparison of the nephelauxetic effects indicate that the silicate matrix provides a more basic environment than either F−or Cl−surroundings found in pure compounds of curium. As a result, f - f transition energies are red shifted significantly in the silicate matrix as compared to that of the neat CmF3system. Moreover, laser induced emissions have been noted with CmF4after treatment at elevated temperatures. The higher energy spectral region, consisting of emission bands at 20100 and 16750, is assignable to f - f transitions in Cm(III), which is the expected thermal decomposition product. Energy transfer from Cm(III), followed by a second photon absorption is believed to be responsible for the strong emission bands at 12550, and 13580 cm−1. from presently unidentified emitting species. Results are discussed in relation to the oxidation state and fluorescence dynamics of actinide species in neat compounds, as well as in matrices being considered for waste immobilization.

An investigation of the effect of poling conditions on the characteristics of screen‐printed piezoceramics

A study of the effect of poling conditions on screen‐printed piezoceramics was undertaken. Printable pastes were produced, using a commercially available lead zirconate titanate (PZT) powder, mixed with two types of binder, lead (II) oxide and a lead borosilicate glass. Sample devices were fabricated using the two paste types and processed, using standard thick film techniques, before being poled under varying conditions. Samples were compared by measurement of piezoelectric charge constant, d33 and using scanning electron microscopy techniques. Temperature and time are shown to increase poling efficiency, while poling field reaches an optimum at 2‐3 MV m‐1. The PZT layers start to fail through a process of dielectric breakdown at fields of 3.5 MV m‐1 and above.

Formulation and characterization of ZnO:Sb thick-film gas sensors

ZnO:Sb based screen printed thick-film H 2, CO and CH 4 gas sensors were fabricated. Films were realized on an alumina substrate by mixing ZnO with lead borosilicate glass frits as a binder and Sb as a catalyst. It was observed that the ZnO:Sb based sensors were more sensitive to these gases than the pure ZnO sensors. The conductance of the sensor increased linearly with the square root of the gas concentration. The dependence of the sensitivity on the amount of the additive (Sb) is discussed. The sensors have a response time of 10 s. Material characterization was carried out by using bulk X-ray diffraction (XRD) and surface morphology by scanning electron microscopy (SEM).

Properties of lead borosilicate glasses: The effect of the structure

A study of the structure and physicochemical properties of lead borosilicate glasses is reported. Consideration is given to the coordination transitions in the glasses and their effect on the properties. A pattern of changes is established in the properties depending on the chemical and phase composition of the glasses.

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, Pb2(Ru2−xPbx)O6.5, whereas the formation of RuO2 is characterized by a platelike morphology instead of initial globular morphology. A general tendency is observed that RuO2 is stable in low‐PbO glass compositions and at high temperatures, while Pb2(Ru2−xPbx)O6.5 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.

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The purpose of present study is to sinter BaTiO3 ceramics at lower temperature than the conventional one. The lower temperature sintering was performed by adding lead boro-silicate glass to BaTiO3, and dielectric properties were evaluated for every content of the glass (0.3. 0.6 and 1.2 mol%). The effects of the glass are more significant in the lower sintering temperature such as 1273K. In particular, 1.2 mol% addition of the glass enhanced a relative permittivity which was 1600 at 1 KHz and a dielectric loss up to 1 MHz were not inferior to those of specimens sintered at 1473 K. The dielectric loss was about 3 % at the frequencies more than 10 kHz. The effects of a glass are discussed with the model for the two phases such as BaTiO3, and grains or pore by the equivalent curcuit.

Low-dielectric compositions with controlled crystallization and thermal expansion

Cristobalite is formed in an initially amorphous low-dielectric lead borosilicate glass at 700–900 °C. With added alumina content greater than a critical value, however, the cristobalite formation in the lead borosilicate glass is completely inhibited. The critical alumina content is found to decrease with decreasing alumina particle size but with increasing sintering temperature. This result is attributed to a strong coupling reaction between Al 3+ from alumina and Na + and Pb 2+ from lead borosilicate glass. The resulting cristobalite-free glass composite has a dielectric constant of 5.0 at 1 MHz and a thermal expansion coefficient of (2.5–4.0) × 10 −6 K −1 in the temperature range of 25–200 °C.

Suppression of crystallization during sintering of lead borosilicate glass powders

Cristobalite is formed when an initially amorphous lead borosilicate glass is sintered at temperatures ranging from 700 to 1000 °C. X-ray diffraction results show that with a sufficient amount of gallium oxide present, however, the precipitation of cristobalite is completely prevented. The amount of gallium oxide required to inhibit cristobalite formation decreases with increasing sintering temperature. The above results are further evidenced by the linear thermal expansion measurement, in which the thermal expansion of the cristobalite-free sample is much smaller than that with cristobalite. The resulting cristobalite-free glass composite has a thermal expansion coefficient of 3.5 × 10 −6 K −1 in the temperature range of 20–200 °C, and a dielectric constant of 5.1 at 1 MHz.

Novel thick-film pH sensors based on ruthenium dioxide-glass composites

Abstract Potentiometric pH electrodes are described, which consist of 30 μm films of a ruthenium dioxide-glass composite, prepared by sintering mixtures of powdered lead borosilicate glass and ruthenium dioxide hydrate onto Pyrex substrates at 900 °C. Electrical contact is made either at a point remote from the solution-contacting portion of the electrode or via a platinum wire contact immediately underlying the active area. Composite electrodes with an RuO 2 :lead borosilicate glass ratio of 1:1 show a near-Nernstian dependence of potential upon pH in aqueous buffer between pH 2 and 12, a maximum hysteresis of 30 mV and a response time of approximately 90 s. Response rates appear to be limited by the diffusion of protons through the porous composite and decrease with decreasing RuO 2 :glass ratio. The composite electrodes are completely indifferent to changes in the concentration of dissolved oxygen, but show a small response to chloride ions. Changes in electrode characteristics with aging are reported, of which the most significant is a −65 mV drift in E 0 .

OH-related capacitance-voltage recovery effect in MOS capacitors passivated by PbOB2O3SiO2GeO2 glasses. The effects of OH content

The purpose of this work is to clarify the relationship between some of the properties of MOS capacitors passivated by lead borosilicate glasses and the hydroxyl contents of the glasses. When PbO content decreased and network forming oxides such as B 2 O 3 , SiO 2 and GeO 2 increased, OH absorption coefficients increased and C - V curve shifts, V G , in MOS capacitors increased. These effects were due to the increase of hydroxyl contents, which depended on the lead borosilicate glass compositions. A good recovery effect in hysteresis loops was observed in MOS capacitors passivated by glasses with a small quantity of hydroxyl ions.

Effect of MgO Addition on the Bondability and Interfacial Reaction between Dielectric and Glass-Ceramics for the Fabrication of Multi-Component Ceramic Substrates

Abstract Bondability and interfacial reaction between dielectric and insulator layers have been examined to obtain a basic understanding of bonding mechanisms. Lead-containing complex perovskite was used as a dielectric material. Two kinds of glass-ceramics were used as insulator material; lead borosilicate glass containing Al2O 3 (insulator A) and the same containing Al2O3 and MgO (insulator B). Dielectric and insulator layers did not bond when insulator A was used. When insulator B was used, however, strong bonding was achieved between the two layers by firing the powder compacts at temperatures between 800° and 1000°C. Addition of MgO to lead borosilicate glass increased the thermal expansion coefficient to that of the dielectric and enhanced the formation of reaction layers, resulting in good bonding. Two reaction layers were identified. The main reaction products were enstatite and bredigite for one layer contacting the dielectric, and enstatite and a compound with the same diffraction pattern as tha...

Ruthenium clusters in lead-borosilicate glass in thick film resistors

An interparticle glass matrix in ruthenium dioxide-based thick film resistors has been studied intensively by means of analytical and high resolution transmission electron microscopy. The ruthenium dioxide phase interacts with lead-borosilicate glass at high temperature by dissolving ruthenium ions and incorporating a small number of lead and aluminum ions on the surface. Ruthenium ions diffuse through the glass network at least over a distance of 1 μm during firing, but are accommodated in the glass structure by an amount only less than 7 at. % at room temperature. High resolution electron microscopy reveals numerous ruthenium-pyrochlore crystallites in high-lead glasses, but hardly any Ru-based clusters/crystallites in low-lead glasses, where lead-rich glass clusters due to glass immiscibility and reduced lead metal clusters are more commonly observed instead of ruthenium clusters. Lead oxide is prone to reduction both in high- and low-lead glasses upon irradiating with a high-energy incident electron beam. Comparison with gold-based resistor and estimation of average dispersion length of ruthenium clusters, 2 to 4 nm, prefer the model of electron hopping via ruthenium clusters/crystallites as a dominant conduction mechanism in thick film resistors.

Sintering of cordierite glass-ceramic with lead borosilicate glass

Two indirect routes used to prepare densely sintered cordierite ceramics are examined. The routes involve sintering of lead borosilicate glass with cordierite glass and with cordierite ceramic, respectively. With the addition of lead borosilicate glass, both cordierite glass powders and ceramic powders can be densified at lower temperature. For cordierite ceramic with lead borosilicate glass, it is observed that Newtonian viscous flow is the predominant mechanism during the initial sintering stage and only densification of glass compacts takes place. However, crystallization of cordierite glass accompanied by the densification of glass compacts occurs during the sintering of cordierite glass with lead borosilicate glass.

Effect of the Addition of Different Metal Oxides in Lead Borosilicate Glasses on the Electrical Characteristics of SbSn Composition-Based Thick-Film Resistors

The paper reports the effect of addition of metal oxides in lead borosilicate glasses on electrical characteristics of SbSn alloy-based thick-film resistors. The Sb and Sn powder (1: 1 by weight) is taken in two quartz tubes separately, vacuum sealed at 10–5Torr and heated in a resistive furnace .at 430℃ and 630℃ respectively. The conventional glass [1] is modified by using different dopants like tungsten oxide, cobalt oxide, lithium oxide, titanium dioxide, venadium pentoxide, chromium oxide, nickel oxide and manganese dioxide. The resistive pastes are formulated with both powders, 5% glass and conventional organic binder. The firing temperature is optimized for eight glasses. The sheet resistivity varies from 1600 Ω/□ to 40 Ω/□ , with negative temperature co-efficient of resistance varying from 2000 ppm/℃ to 800 ppm/℃ respectively. Material characterization is carried out using the XRD technique. Aging studies of resistors at room temperature over the period of two months indicate that these resistors stabilize within 15–20 days.

Ostwald Ripening of Silver in Lead-Borosilicate Glass

Ostwald Ripening of Silver in Lead-Borosilicate Glass

Densification and Dielectric Properties of Cordierite-Lead Borosilicate Glasses

To improve the sinterability of P2O5-added cordierite glass, lead borosilicate glass was adopted as a sintering aid. Various sintering temperatures and times were used to observe the effects of heat treatments on the sintering behavior of the cordierite-lead borosilicate glass. The flux effect of lead borosilicate glass aids the coalescence of cordierite glass particles, which promotes the densification. Phase transformation from cordierite glass to the high-temperature α-cordierite form is the major reaction during the sintering of cordierite-lead borosilicate glass. The dielectric constant of the sintered composites is determined by both the existing crystalline structure and the completeness of densification. The relationship between the volume fraction of lead borosilicate glass and the dielectric constant can be approximated by a linear equation.

Effect of Additives on Ostwald Ripening of Silver in Glass

The effect of additives on the growth of silver particles in a lead borosilicate glass was studied. Growth of silver particles was expressed by the Ostwald ripening theory and controlled by diffusion. Addition of palladium retarded the growth of silver particles. This is attributed to the reduced activity of silver caused by the formation of silver–palladium solid solutions. Addition of ruthenium dioxide promoted the growth, whereas addition of tin dioxide had almost no effect on the growth rate. A “solubility parameter” was introduced to evaluate the temperature dependence of solubility of silver in glass, and the effect of additives has been discussed. Association of diffusion species has been proposed as a possible factor responsible for the temperature dependence of the solubility parameter.

Effect of Temperature on Ostwald Ripening of Silver in Glass

The effect of temperature and volume fraction on the growth of silver particles in a lead borosilicate glass has been studied. The particle growth obeyed the Ostwald ripening theory and was controlled by diffusion. An anomaly of growth rate coefficient was observed around 700°C and explained in terms of the dissolution behavior of silver. Also, the solubility of silver in glass was evaluated from the normalized rate coefficient K using volume fraction of silver particles and viscosity of the glass.

Effect of additives on the properties of the lead-borosilicate glasses and the thin-film coatings based on them

Effect of additives on the properties of the lead-borosilicate glasses and the thin-film coatings based on them

Photoconductivity of PbO-doped borosilicate glass prepared by the sol-gel process

Partially crystallized lead borosilicate glasses were prepared from 0.65PbO 0.20B 2O 3 0.15SiO 2 gels. The microstructure and photoconductive characteristics of the materials thus obtained were studied. Photoconductive measurements performed on films (200–250 μ m thick) indicate an efficiency (1.73) higher than that (1.45) obtained on homologous glass-ceramics prepared by melting of oxides at T > 900°C.