PbO SiO2 Research Articles

The production of a lead glaze with galena: Thermal transformations in the PbS–SiO2 system

AbstractGalena, also known as PbS, was widely used in the production of lead glazes from the beginning of the 18th century to the second half of the 20th century. Although the PbO‐SiO2 system has been studied for years, the PbS–SiO2 phase diagram, involved in the formation of a glaze with galena, has not yet been investigated. Temperature transformations for the system 75 wt% PbS‐25 wt% SiO2 are investigated in a high‐temperature resolved X‐ray diffraction experiment with synchrotron radiation and compared to those of the equivalent system 70 wt% PbO‐30 wt% SiO2. Lanarkite, PbO·PbSO4, is the phase predominantly formed as soon as galena decomposes during the heating. The results show that the system melts at a temperature higher than the PbO–SiO2 system, but far lower than those expected for the PbO–PbSO4–PbS system. A historical misfired lead glaze produced with galena is also studied. The presence of galena, lanarkite, and mattheddleite, Pb10(SiO4)3.5(SO4)2Cl2, is determined and discussed in terms of the composition of the galena mineral used and the firing conditions in light of the high‐temperature transformations previously obtained.

Correlation model to estimate the thermodynamic properties

A technique for constructing the correlation dependencies of the thermodynamic properties of similar compounds was proposed. This technique is based on the Taylor expansion in the supposed analytic relationship between properties. The constructed correlation dependencies were used to estimate the thermodynamic properties of the condensed bromides and iodides of hafnium HfGn (G [Formula: see text] Br, I and [Formula: see text], 2, 3, 4) and the compounds formed in the PbO–SiO2 system. Standard formation enthalpy [Formula: see text], entropy [Formula: see text], heat capacity [Formula: see text] and temperature dependencies [Formula: see text] at temperatures T[Formula: see text][Formula: see text]k to 3000[Formula: see text]k were estimated. The standard estimation error of the thermodynamic properties of the compounds in the PbO–SiO2 system does not exceed 2% for all the estimated properties. For condensed halides, the standard estimation error was (1) [Formula: see text]% for enthalpy, (2) [Formula: see text]% for entropy, (3) [Formula: see text]% for heat capacity.

Up-Conversion Luminescence in Oxyfluoride Glass-Ceramics with PbF2:(Yb3+, Eu3+, RE3+) (RE = Tm, Ho, OR Er) Nanocrystals

Transparent oxyfluoride glass-ceramics containing PbF2:(Yb3+, Eu3+, RE3+) (RE = Tm, Ho, Er) nanocrystals were synthesized by secondary thermal treatment of low-melting SiO2–PbO–PbF2–CdF2 glasses. The optical absorption and luminescence of the rare earth ions were investigated. Multi-color (orange, yellow, green, and blue) upconversion luminescence was detected with excitation at 960 nm by an InGaAs laser diode. The luminescence color characteristics could be controlled by varying the heat treatment regime.

Surface crystallization behavior during thermal processing of low-photoelastic ZnO–SnO–P2O5 glasses

Pb-containing glasses such as the PbO–SiO2 series are useful in optical devices because of their low-photoelastic constants (PECs); however, the toxic Pb component in these glasses is problematic. Transparent ternary ZnO–SnO–P2O5 glasses are potential substitutes for low-PEC Pb-containing glasses, but their thermal behavior is not well understood, which inhibits their ability to be drawn into fibers. Herein, we report the surface crystallization behavior of transparent ternary ZnO–SnO–P2O5 glasses, including those with low-PEC compositions, heated under isothermal conditions to temperatures above their glass-transition temperatures. The crystallization conditions for low-PEC phosphate glasses during their thermal processing into shapes of optical modules were deduced. The crystalline compounds precipitated on the surfaces were investigated via X-ray diffraction analysis, micro-Raman spectroscopy, and microscopic observations. A time–temperature–transformation diagram was constructed on the basis of the thermal stability of the glasses. We expect that this enhanced understanding of the crystallization behavior induced by the reshaping process will enable fabrication of precise polarization control devices with low PECs, such as optical-fiber current sensors, optical lenses, and filters.

Elasto-Optic Coefficients of Borate, Phosphate, and Silicate Glasses: Determination by Brillouin Spectroscopy

The elasto-optic tensor elements p12 and p44 of glasses in the series BaO–B2O3, PbO–B2O3, BaO–P2O5, PbO–P2O5, and PbO–SiO2 were measured using Brillouin spectroscopy. Densities, refractive indices, and elastic moduli were also determined. A model was also developed for the elasto-optic tensor elements based on a bond-polarizability approach, which was validated using first-principles calculations and then used to explain the compositional trends observed in the elasto-optic tensor elements. It was found that the shear elasto-optic element p44 could be explained in terms of the average bond polarizability anisotropy, while the dilation response p11 + 2p12 involved also the bulk cell polarizability response to volume changes.

Spectral and Luminescent Properties of Oxyfluoride Glasses Codoped with (Yb3+, Eu3+) and (Yb3+, Tb3+)

The spectral and luminescent properties of SiO2–PbO–PbF2–CdF2 oxyfl uoride glasses doped with Yb3+, Eu3+, and Tb3+ were investigated. The lifetime τ( 5D0) of Eu3+ in glasses doped with Eu2O3 was 1.73 ms; τ( 5D4) of Tb3+, 2.25 ms. Intense red and green up-conversion luminescence due to cooperative energy transfer from Yb3+—Yb3+ pairs to Eu3+ and Tb3+ was observed for glasses codoped with (Yb3+, Eu3+) and (Yb3+, Tb3+) upon excitation at 960 nm into the Yb3+ absorption band. Down-conversion luminescence of Yb3+ ions in the vicinity of ~1 μm was detected upon excitation by UV light of wavelength 355 nm.

Luminescence of Oxyfluoride Glasses Containing Yb3+–RE3+ Ions

The optical absorption and up-conversion luminescence of oxyfluoride glasses in the system SiO2–PbO–PbF2–CdF2 coactivated by Yb3+–RE3+ ions (where RE = Er, Tm, Ho, Dy, Pr, or Tb) are investigated. Excitation with a laser diode in the IR range (960 nm) gives intense green, blue, and red luminescence. The color characteristics of the up-conversion luminescence in the CIE 1931 system are determined. The efficiency of energy transfer from the Yb3+ to the RE3+ ions is found to be 70% for RE = Er, Tm, and Ho. The efficiency of cooperative energy transfer reaches 10% for glass with Yb–Tb ions.

The effect of a temperature gradient on the phase formation inside a magnesia–chromite refractory in contact with a non-ferrous PbO–SiO2–MgO slag

Furnace relinings represent a major operating cost in pyrometallurgy. External cooling is, therefore, often used to reduce the chemical wear by limiting the slag infiltration depth, reducing the reaction kinetics and lowering the solubility of refractory components into the liquid slag. In this paper a new experimental setup is used to study the reaction between a synthetic PbO–SiO2 based slag and a magnesia–chromite refractory under a temperature gradient. Forsterite (Mg2SiO4) is formed throughout the sample, removing SiO2 from the infiltrated liquid slag. The resulting change in slag composition causes the liquidus temperature and the viscosity of the liquid to decrease partially countering the effect of the applied temperature gradient and resulting in the complete infiltration of the sample. The extent to which external cooling prolongs the lifetime of an industrial furnace thus depends on the slag properties and how they are modified after reaction with the refractory.

Synthesis and luminescence properties of Ce:Y3Al5O12 glass ceramic by spontaneous crystallization

Transparent Ce: Y3Al5O12 glass ceramics were successfully fabricated via spontaneous crystallization of a Ce3+-doped PbO–SiO2–Al2O3–Y2O3–B2O3 glass during melt-quenching. The transparency of the samples was improved with increasing the Pb/Si atomic ratio. With the increase of Ce3+ content, the emission peak shifted towards the long wavelength and the luminous efficacy was gradually enhanced. Such glass ceramic-based white-light-emitting diode yielded a luminous efficacy of 97lm/W, a correlated color temperature of 5561K and a color rendering index of 69.3.

Prediction of the thermodynamic functions of mixing of binary oxide melts in the PbO–SiO2, Al2O3–SiO2 and CaO–Al2O3 systems by structure-based modification of the quasi-chemical model

A structure-based modification of the Guggenheim's quasi-chemical model for the prediction of the thermodynamic functions of mixing in binary silicate and aluminate melts is presented and the extension of this approach to ternary systems is discussed. Based on the “anionic” point of view on the oxide melts structure, the novel method for determination of the interchange energy (a principal parameter of the quasi-chemical theory) was proposed along with a simple and general set of the equations. The activity calculations of the end-member components and integral and partial enthalpies and Gibbs free of mixing along with the whole range of compositions for PbO–SiO2 and Al2O3–SiO2 systems as well as the model calculations of components in CaO–Al2O3 melts were made. The reasonable agreement between results of model calculations and experimental data showed the reliability of this approach in predicting of the thermodynamic functions of mixing in binary and aluminate systems. This approach has the advantage that prior knowledge of the experimental mixing properties of liquid oxide systems is not required.

Cooperative up-conversion in Eu3 +,Yb3 +-doped SiO2–PbO–PbF2–CdF2 oxyfluoride glass

Novel oxyfluoride glass doped with YbF3 and Eu2O3 is synthesized in the SiO2–PbO–PbF2–CdF2 system by melt-quenching technique. Its physical properties, as well as the optical absorption of Eu3+ and Yb3+ ions are studied. Spectroscopic properties of Eu3+ ions are modeled within modified Judd–Ofelt theory, yielding absorption oscillator strength, luminescence branching ratios and radiative lifetime of 5D0 state. Intrinsic emission of Eu3+ ions under direct excitation in the UV, as well as up-conversion luminescence under near-IR excitation via cooperative energy transfer, 2Yb3+→Eu3+, are studied. In the latter case, the glass provides intense reddish-orange emission with CIE coordinates x=0.636, y=0.363. The asymmetry parameter R for Eu3+ emission in the studied glass is about 8. The efficiency of this transfer mechanism is estimated from shortening of 2F5/2(Yb3+) lifetime to be 10±1%.

New Luminescing Oxyfluoride Glass with Europium and Ytterbium Ions

New oxyfluoride glasses containing Eu3+ and Yb3+have been synthesized in the system SiO2–PbO–PbF2–CdF2 and their physical-chemical properties and the optical absorption and up-conversion of luminescence have been studied. Intense orange-red luminescence (color coordinates x = 0.64, y = 0.36) peaking near 612 nm was obtained by excitation in the IR range by a commercially available laser diode. This glass is promising for obtaining nano-phase luminescing glass-ceramics for use in up-conversion luminophores and solid-state lasers.

Study of crystallization process of soda lead silicate glasses by thermal and spectroscopic methods

The crystallization process of some glasses in the ternary Na2O–SiO2–PbO system with good chemical stability that can be used for waste inertization was studied using X-ray diffraction (XRD), infrared spectroscopy (FT-IR), differential thermal analysis (DTA) and scanning electron microscopy. The parent glasses were characterized by XRD and FT-IR, and their vitreous state was determined. DTA measurements evidenced glass transition (T g) and crystallization temperatures (T c). The thermal treatments were conducted at vitreous transition temperature (400 °C) and at highest effect of crystallization (650 °C). XRD evidenced the lead and sodium silicate crystalline phases in samples treated at 650 °C for 12 h. Micrometer crystallites dispersed in the glass matrices have affected the transparence of glasses and made them opaque after treatment at 650 °C. The influence of oxide quantities in compositions on the crystallization tendency was revealed. A PbO higher content than that of SiO2 as well as lower Na2O content decreased the tendency of crystallization.

The effect of phase formation during use on the chemical corrosion of magnesia–chromite refractories in contact with a non-ferrous PbO–SiO2 based slag

Abstract One of the main factors limiting the lining lifetime in pyrometallurgical smelters is continuous refractory oxides dissolution in the slag bath. The overall wear is accelerated when the slag infiltrates the porous brick and the dissolution thus occurs in a larger part of the lining. This work investigates the possibility of preventing deep infiltration by sealing off the pores with newly formed phases. Static finger tests at constant temperature (1200 °C) were performed in contact with a synthetic non-ferrous PbO–SiO 2 –MgO slag, showing the formation of forsterite (Mg 2 SiO 4 ) throughout the refractory sample by the reaction between SiO 2 (slag) and MgO (refractory). This phase grows with time, eventually sealing off the pores near the interface with the bath. The phase grows too slow to prevent full infiltration of the refractory but creates an equilibrium state in the sealed off part of the sample, ceasing the chemical corrosion in that part of the sample.

Electronic conductivity in the SiO2–PbO–Fe2O3 glass containing magnetic nanostructures

The linear impedance spectra of iron–silicate–lead glass samples were measured in the frequency range from 1 MHz to 1 MHz and in the temperature range from 153 K to 423 K. The structure was investigated by means of XRD and atomic force microscopy. Local electrical and magnetic properties of the samples were tested with the aid of electrostatic force microscopy (EFM) and magnetic force microscopy (MFM). The obtained results show that the impedance spectra of all samples exhibit one large relaxation process and some additional small relaxation is present in glass containing 20 mol% and 25 mol% Fe2O3. The AFM micrographs show that in a subset of samples some nanostructures exist. Their size, shape, and quantity depend on the amount of Fe2O3 in the composition of the glass. The samples containing an amount of 15 mol% of Fe2O3 include the biggest nanostructures which are ball-shaped. EFM and MFM micrographs show that nanostructures exhibit different electrical and magnetic behaviors than the rest of the glass matrix. On the basis of Jonscher universal dielectric response the temperature dependence of conductivity exponent s was determined and compared to theoretical models proposed by Elliott. It was found that while in the glass containing less than 15 mol% iron oxide, there is only one process responsible for conduction mechanism, the overlap polaron tunneling. In the other samples, a different conduction mechanism may coexist: quantum mechanical tunneling between semiconducting granules.

Comparative study of gamma ray shielding and some properties of PbO–SiO2–Al2O3 and Bi2O3–SiO2–Al2O3 glass systems

Gamma-ray shielding properties have been estimated in terms of mass attenuation coefficient, half value layer and mean free path values, whereas, structural studies have been performed in terms of density, optical band gap, glass transition temperature and longitudinal ultrasonic velocity parameters. X-ray diffraction, UV–visible, DSC and ultrasonic techniques have been used to explore the structural properties of PbO–SiO2–Al2O3 and Bi2O3–SiO2–Al2O3 glass systems.

The de-clustering influence of aluminum ions on the emission features of Nd3+ ions in PbO–SiO2 glasses

Nd3+ doped lead alumino silicate glasses with varying concentration of Al2O3 (from 5 to 10mol%) have been synthesized. The IR and Raman spectral studies of these glasses have indicated that there is a gradual increase in the depolymerization of the glass network with increase in the concentration of Al2O3. The optical absorption, luminescence spectra and fluorescence decay curves of these glasses were recorded at room temperature. From these studies, the radiative parameters viz., spontaneous emission probability A, the total emission probability, the radiative lifetime τ, the fluorescent branching ratio β of different transitions originated from 4F3/2 level of Nd3+ ions have been evaluated. A clear increase in the quantum efficiency and luminescence emission of the two prominent NIR bands of Nd3+ ions viz., 4F3/2→4I11/2, 13/2, is observed with increase in the concentration of Al2O3. The increase has been attributed to the possible admixing of wavefunctions of opposite parities and due to the declusterization of Nd3+ ions by Al3+ ions in the glass network.

Structural and optical aspects for Eu3+ and Dy3+ ions in heavy metal glasses based on PbO–Ga2O3–XO2 (X = Te, Ge, Si)

Structural and optical properties of Eu3+ and Dy3+ ions in PbO–Ga2O3–XO2 (X=Te, Ge, Si) glasses have been examined using X-ray diffraction, FT-IR and luminescence spectroscopy. Several crystalline phases such as TeO2, PbTe3O7, PbO and PbO2 were identified in lead tellurite system using X-ray diffraction analysis, in contrast to PbO–Ga2O3–XO2 (X=Ge, Si) glass samples. Characteristic emission bands due to the 5D0→7FJ (J=0–4) transitions of Eu3+ and the 4F9/2→6HJ/2 (J=15, 13, 11) transitions of Dy3+ were registered. Two spectroscopic parameters, such as luminescence intensity ratios associated to 5D0→7F2 and 5D0→7F1 transitions of Eu3+ as well as 4F9/2→6H13/2 and 4F9/2→6H15/2 transitions of Dy3+, and luminescence lifetimes for excited states of rare earth ions were determined. The luminescence intensity ratios for Eu3+ and Dy3+ ions decrease, whereas 5D0 (Eu3+) and 4F9/2 (Dy3+) luminescence lifetime increases, when covalence between Ln3+ and O2− ions is reduced and the phonon energy of the host glass is increased in PbO–TeO2→PbO–GeO2→PbO–SiO2 direction. It was confirmed by FT-IR measurements.

A facile method to prepare multifunctional PBO fibers: simultaneously enhanced interfacial properties and UV resistance

A new method combining surface coating with chemical grafting to prepare poly(p-phenylene benzobisoxazole) fiber–silica–graphene oxide (PBO–SiO2–GO) hybrid fiber was proposed. The chemical composition, surface morphology, surface roughness (Ra), surface energy, interfacial shear strength (IFSS), single filament tensile strength (TS) and ultraviolet (UV) resistance of PBO fibers before and after modification were investigated. Experimental results revealed that the PBO fiber surface was covered by a silica coating, onto which GO was successfully grafted through chemical bonds. The Ra and surface energy of PBO–SiO2–GO were obviously increased in comparison with that of an untreated one. The IFSS of its composites was greatly improved due to the excellent wettability and mechanical interlocking of GO. Meanwhile, TS had no obvious decrease after the surface coating and grafting process. Moreover, the introduction of silica coating on the fiber surface led to a better UV resistance than that of an untreated one. We believe this effective method may provide a novel surface modification strategy for developing multifunctional fibers.

Correlation of structural units and chemical stability in SiO2–PbO–Na2O ternary glasses: Spectroscopic methods

Several compositions in the vitreous SiO2–PbO–Na2O system, with 12.8–25mol% PbO and 21–34.6mol% Na2O were prepared by a conventional melt-quenched method. The structure of the obtained glasses was investigated by Infrared (IR), Raman and X-ray photoelectron spectroscopy (XPS) that have underlined the vitreous state of the samples and the differences in the structural units depending both on PbO and Na2O content. The structural units present in the glasses were evidenced by bands' deconvolution in the IR and Raman spectra. The structural correlations in this ternary system are a real challenge, as the behavior of the compositions selected in the ternary system is totally different of that of the binary systems PbO–SiO2 and Na2O–SiO2. ICP-AES results on the aqueous solutions obtained from the studied glasses have shown different chemical stability in water related with extracted ions. The results could be correlated to the glasses structure, namely to the role played of PbO in the structure.