PbO B2O3 Research Articles

PbO–B2O3–SiO2 glass powders with spherical shape prepared by spray pyrolysis

PbO–B2O3–SiO2 glass powders were directly prepared using spray pyrolysis. The powders were spherical and fine-sized. One glass particle was obtained from one droplet by melting the precursors inside a hot wall tubular reactor. The characteristics of these powders were compared with those of the commercial product, which was prepared using the conventional melting process. The spherical powders, which were prepared using spray pyrolysis at 1000°C, had broad peaks at around 28° in the XRD spectrum. The glass phase was formed during the spray pyrolysis process even within a short residence time of the powders inside the hot wall tubular reactor. The mean size of the prepared glass powders was 1μm. The dielectric layers formed from the spherical, fine-sized glass powders had a high transparency at firing temperatures above 520°C. The maximum transparency of the dielectric layer formed from the glass powders obtained from spray pyrolysis was 95.3% at the firing temperature of 560°C. The dielectric layer formed from the spherical, fine-sized glass powders had a smooth surface and no void inside the dielectric layer.

Spectroscopic study of Eu3+ ions in heavy metal fluoride and oxide glasses

AbstractTwo types of fluoride and oxide systems belonging to the heavy metal glass family have been studied. From absorption and emission spectra together with Judd–Ofelt analysis, spectroscopic parameters of Eu3+ ions in both optical systems were evaluated and compared. The new oxide glassy system based on PbO–B2O3–Al2O3–WO3 exhibits interesting spectroscopic properties of Eu3+ ions for application as a red‐emitting optical material. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Elastic properties of fast ion conducting lithium based borate glasses

Elastic properties of Li2O–PbO–B2O3 glasses have been investigated using sound velocity measurements at 10MHz. Four series of glasses have been investigated with different concentrations of Li2O, PbO and B2O3. The variations of molar volume have been examined for the influences of Li2O and PbO. The elastic moduli reveal trends in their compositional dependence. The bulk and shear modulus increases monotonically with increase in the concentration of tetrahedral boron which increases network dimensionality. The variation of bulk moduli has also been correlated to the variation in energy densities. The Poisson’s ratio found to be insensitive to the concentration of tetrahedral boron in the structure. The experimental Debye temperatures are in good agreement with the expected theoretical values. Experimental observations have been examined in view, the presence of borate network and the possibility of non-negligible participation of lead in network formation.

Tailoring the Microwave Dielectric Properties of Ca5Ta2TiO12 Ceramics Through Glass Addition

Microwave dielectric properties of polycrystalline Ca5Ta2TiO12 ceramics have been tailored using different glass additives. Several glasses such as B2O3, SiO2, B2O3–SiO2, ZnO–B2O3, Al2O3–SiO2, Al2O3–B2O3–SiO2, BaO–B2O3–SiO2, MgO–B2O3–SiO2, ZnO–B2O3–SiO2, PbO–B2O3–SiO2, and 2MgO–Al2O3–5SiO2 were added to calcined Ca5Ta2TiO12 powder in different weight percentages. Among these glasses, addition of 0.1 wt% of SiO2, Al2O3–SiO2, Al2O3–B2O3–SiO2, MgO–B2O3–SiO2, and 2MgO–Al2O3–5SiO2 improved the microwave dielectric properties. Fluxing of Ca5Ta2TiO12 with 0.1 wt% of 2MgO–Al2O3–5SiO2 glass has ɛr=39, Qu×f>40 000 at 5 GHz and τf=+8 ppm/°C. Near‐zero τf was obtained with the addition of glasses like Al2O3–SiO2, Al2O3–B2O3–SiO2, MgO–B2O3–SiO2, and 2MgO–Al2O3–5SiO2. Addition of all the glasses except BaO–B2O3–SiO2 reduced the τf of Ca5Ta2TiO12 ceramics. Two weight percent glass addition to Ca5Ta2TiO12 ceramics reduced their sintering temperature down to 1450°C from 1625°C and τf close to zero but deteriorated the ɛr and unloaded quality factor. The effects of glass content on the structure and microstructure of Ca5Ta2TiO12 ceramics were studied by X‐ray diffraction and scanning electron microscopic techniques.

Growth and magnetic properties of LPE-grown (EuTbBi)3(FeAlGa)5O12 garnet films

Using the PbO–B2O3–Bi2O3 flux system, (EuTbBi)3(FeAlGa)5O12 (EuTbIG) films were grown on (GdCa)3(GaMgZr)5O12 (SGGG) substrates for optical devices by the liquid phase epitaxial (LPE) method. The grown films' growth and magnetic domain wall were observed as a function of the Fe2O3/(Al2O3+Ga2O3)(R2) molar ratio by magnetic force microscope (MFM). As the grown films decreased the R2 molar ratio, the saturation magnetization of the grown films showed a tendency to decrease from 250 to 150 Oe. Also, we observed that the R2 molar ratio did not affect the surface morphology and thickness of the grown films, but it did affect the magnetic domain wall.

Growth of Single Crystals of High-Curie-Temperature Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 Ternary Systems near Morphotropic Phase Boundary

Crystal growth in xPb(In1/2Nb1/2)O3–yPb(Mg1/3Nb2/3)O3–zPbTiO3 (PIMNT100x/100y/100z) ternary systems near the morphotropic phase boundary was investigated by the conventional flux method using PbO and PbO–B2O3 flux. The PIMNT crystals were obtained easily by the slow cooling of a 50PIMNT:40PbO:10B2O3 (mol%) molten solution from 1230°C to 850°C. The PbO–B2O3 flux is effective for PIMNT single crystal growth. The largest PIMNT 16/51/33 crystal had dimensions of about 20 mm × 10 mm × 5 mm. The (001) wafers cut from the obtained crystal had transparent and opaque areas. The electron probe X-ray microanalysis (EPMA) results revealed that the compositions of the two areas differ slightly; the Ti content in the opaque area is lower than that in the transparent area. The temperature dependence of the dielectric constant showed a maximum at the tetragonal to cubic phase-transition temperature (Tc=187°C), which is 30°C–40°C higher than that for a 0.68Pb(Mg1/3Nb2/3)O3–0.32PbTiO3 (PMNT 68/32) single crystal. A dielectric constant (ε33T/ε0) of 4000, a coercive field (Ec) of 7.0 kV/cm, an electromechanical coupling factor (k33') of 80%, and a frequency constant (N33'r) of 1160 Hzm were obtained.

Thermal, Dielectric, and Optical Properties of Neodymium Borosilicate Glasses for Thick Films

Because of their thermal, dielectric, and optical properties, new glass compositions and thick‐filmed transparent dielectrics containing neodymium oxide (Nd2O3) were studied as a source of purer images in plasma display panels. In the present study, PbO–B2O3–SiO2 and PbO–B2O3–SiO2–ZnO–Al2O3 were used as starting glass compositions, to which up to 25 wt% of Nd2O3 then was added. Increased amounts of Nd2O3 increased the glass transition temperature and dielectric constant of the bulk glasses and decreased the coefficient of thermal expansion. The fired thick films (around 30 μm) allowed selectively visible light to penetrate and showed deep absorption properties at 585 nm that were related to an extraneous gas from neon discharge.

Properties of epitaxial yttrium iron garnet films grown from BaO flux

Yttrium iron garnet, Y3Fe5O12, films of excellent purity were grown onto Gd3Ga5O12 substrates by liquid phase epitaxy from a lead-free BaO–B2O3–BaF2 flux. The aim of using the BaO flux was to reduce the content of impurities and intrinsic defects in the garnet films and to obtain samples with minimum microwave losses. The films were characterized by the nuclear magnetic resonance (NMR), ferromagnetic resonance, and parallel pumping method. The NMR spectra demonstrated a considerable reduction of impurity concentration compared to garnet films produced from a conventional PbO–B2O3 flux. Likewise, the NMR and spin wave linewidths of BaO-grown films were very narrow comparable with results obtained on the best (111) films and bulk samples.

Crystal Growth and Some Properties of Lead Indium Niobate-Lead Titanate Single Crystals Produced by Solution Bridgman Method

A single crystal about 15 mm in diameter and 10 mm in length of the lead indium niobate-lead titanate, (1-x)Pb(In1/2Nb1/2)O3–xPbTiO3[PIN–PT(1-x/x)] solid solution system near a morphotropic phase boundary was obtained by the solution Bridgman method using PbO–B2O3 flux. X-ray diffraction study reveals that the ingot cut perpendicularly to the cylindrical as-grown PIN–PT(63/37)(the starting composition) single crystal length exhibits the (110) plane of the perovskite phase, and the wafers cut 2 mm and 10 mm from the bottom of the cylindrical PIN–PT single crystal exhibit the rhombohedral phase and tetragonal one at room temperature, respectively. The crystal growth was almost along the [110] direction. The Ti contents x of these wafers cut at 2 mm and at 10 mm were determined by Inductive Charge Plasma (ICP) chemical analysis to be 0.31 and 0.35, respectively. The Ti content of the as-grown PIN–PT(63/37)(the starting composition) single crystal was found to increase with growth away from the nucleation point. For x=0.31, the relative permittivity εr has a peak (37000 at 10 kHz) at the Curie temperature Tc, 300°C and then a shoulder at the ferroelectric rhombohedral to tetragonal phase transition temperature, 120°C with cooling. For x=0.35, the εr has a peak (25000 at 10 kHz) at Tc, 313°C.

Optical and transport properties of thin sheets of CuO–PbO–B2O3 glasses

Different xCuO–(50−x)PbO–50B2O3 glasses were prepared. The optical transport properties of thin sheets were investigated. The optical density and the transmission showed a large band peaking at the wavelengtgh λ≈800nm and a noticeable coloring corresponding to λ=500nm. The high-frequency dielectric constant and the refractive index were calculated from the reflection using a computer program. The electrical measurements carried out showed semiconductor behavior of the conductivity as a function of temperature. The activation energies (Ea) for the conduction process indicated a thermally activated hopping mechanism. The calculated Ea values are typically 0.72–0.82eV. They are higher than those calculated from the optical measurements (0.62–0.7eV).

Synthesis of Glass-Ceramic Materials in the BaO–PbO–B2O3–Al2O3–TiO2 System

The influence of PbO, B2O3, and Al2O3 additives on the glass formation and crystallization of glasses with a high total content of BaO and TiO2 (65–75 wt % or 76–86 mol %) is investigated. It is shown that glasses of the compositions (wt %) 31–35 BaO, 12–17 PbO, 34–42 TiO2, 10–13 Al2O3, and 2–3 B2O3 are promising materials for use in preparing glass-ceramic ferroelectrics based on the melting–molding–crystallization technology. These compounds are characterized by a relatively low melting temperature (1450°C), the absence of spontaneous crystallization during molding, and the possibility of controlling the phase composition of the material through the appropriate choice of the crystallization temperature.

Structural Study of PbO–B2O3 Glasses by X‐ray Diffraction and 11B MAS NMR Techniques

The structure of PbO–B2O3 glasses has been investigated in the composition range of 25–80 mol% PbO by using X‐ray diffraction and 11B NMR techniques. The well‐separated peaks due to Pb–O and Pb–Pb pairs were first observed in the radial distribution function, and peak deconvolution was performed by using a pair function method. The average coordination number of lead atoms was determined to be about 6 in the low‐PbO‐content region and about 3 in the high‐PbO‐content region. With an increase of PbO content, the peaks at 0.24 and 0.40 nm shifted to shorter distances, and especially the latter peak drastically increased in intensity in the composition range >50 mol% PbO. It was suggested that PbO is a main glass former in the high‐PbO‐content region. Based on the results obtained, we propose structural models of lead borate glasses.

Single Phase Ba2Ti9O20 Microwave Dielectric Ceramics Prepared by Low Temperature Liquid Phase Sintering

Microwave dielectric ceramics of Ba2Ti9O20 were prepared by adding PbO–B2O3–SiO2 (PBS) as a liquid phase sintering aid. With the addition of 5 wt% PBS, dense and single-phase Ba2Ti9O20 dielectric resonators could be fabricated at a sintering temperature below 1200°C. The microwave dielectric properties of PBS–Ba2Ti9O20 ceramics were found to depend upon the density, the amount of liquid phase and the sintering temperature. Although glass addition results in a decrease of the dielectric properties, the sintered PBS–Ba2Ti9O20 ceramics still exhibit much better dielectric properties than that of pure Ba2Ti9O20 ceramics at low sintering temperatures.

Structural Role of PbO in Li2O–PbO–B2O3 Glasses

Thermal and spectroscopic studies have been carried out on a number of glasses with wide ranging compositions in the pseudoternary glass system Li2O–PbO–B2O3 in order to understand the structural role of PbO in these glasses. Infrared, Raman, and 11B MAS-NMR results indicate that PbO behaves as a network former in these glasses and is possibly incorporated in the network as [PbO4/2]2− units. The formation of [PbO4/2]2− units leads to the creation of neutral three-coordinated boron (B03) which, in turn, leads to the reformation of four-coordinated boron (B−4) in the structure at the expense of two-coordinated (B−2) and singly coordinated (B2−1) boron atoms. The variations of glass transition temperatures (Tg) and molar volumes also support this model.

Effect of Glass Addition on Microwave Properties of BaO·La2O3·4.7TiO2

The effects of the addition of glass to the microwave properties of BaO·La2O3·4.7TiO2 ceramics were investigated. Three commercial glasses: PbO–B2O3–SiO2 (GA9), ZnO–B2O3–SiO2 (GP032) and PbO–B2O3 (LS3081), were investigated in this study. The ceramics without glass addition and sintered at 1300°C gave the relative dielectric constant εr=92, quality factor Q=1653 and temperature coefficient of resonant frequency τf=40.3 ppm/°C at 3.0 GHz. With 20 wt% GA9 addition, highly dense samples (void fraction were ≤2.5 vol%) were obtained at Ts≥900°C and their microwave properties were: εr≥64, Q≥1037 and τf≤15.3 ppm/°C at 3.0 GHz. The high sintering temperature increased εr and Q values but decreased the value of τf. The densification of specimens was found to play an important role in improving the dielectric constant. Heterogeneous interfaces and the dissolution of trace amounts of ceramics in glass increased the dielectric loss significantly; also, the former increased τf whereas the latter decreased it.

Screen Printed La2/3Sr1/3MnO3 Thick Films on Alumina Substrates

We report here on the preparation of La2/3Sr1/3MnO3 magnetoresistive thick films on polycrystalline Al2O3 substates by using the screen printing technique. It is shown that films can be obtained using high temperature sintering. While there is a reacted layer, this improves adhesion and is not too troublesome if the films are made thick enough. It is shown that PbO–B2O3 –SiO2 glass additives allow sintering at lower temperatures and can be used to improve the mechanical stress of the films. However, it is found that glass concentrations large enough to significantly improve the film adherence result in a weak low field magnetoresistance probably because grains are coated with high resistivity material. Strategies to overcome these difficulties are discussed.

Semiconducting BaTiO3 ceramic prepared by low temperature liquid phase sintering

Donor-doped BaTiO3 ceramics were prepared by adding PbO B2O3 SiO2 as a sintering aid. Semiconducting BaTiO3 was obtained at a sintering temperature of 1100 °C. The sintered samples exhibit the Positive Temperature Coefficient of Resistivity (PTCR) effect, which depends on the amount of liquid phase, the concentration of the donor-dopant, and the sintering temperature. The cold resistivity of the samples decreases when the sintering temperature increases. The increase of the grain boundary resistivity and hence of the cold resistivity at lower sintering temperatures was explained by applying the diffusion grain boundary layer model.

Preparation by a Sol–Gel Process and Dielectric Properties of Lead Zirconate Titanate Glass-Ceramic Thin Films

Ferroelectric glass-ceramic thin films of PbZr0.5Ti0.5O3(PZT)–PbO–B2O3, PZT–PbO–SiO2 and PZT–PbO– SiO2–B2O3 were produced by a sol-gel process. A pin-hole-free thin film of 300–500 nm thickness on a Pt/Ti/ SiO2/Si substrate was obtained having a structure in which small PZT crystals developed in a glass matrix. A high PZT content, of more than 80%, was achieved at levels unattainable by a conventional glass-ceramics preparation method. The perovskite-type PZT crystallized at around 500° C in the pure PZT, PZT–PbO–B2O3, and PZT–PbO–SiO2–B2O3 systems and at around 700° C in the PZT–PbO–SiO2 system. The dielectric properties of the 0.835PZT–0.165(3PbO·SiO2·B2O3) film fired at 700° C with gold electrodes were ε=1000, and tan δ=0.035.

The valence states and magnetic interactions between manganese ions in TeO2PbOB2O3 glasses

The temperature dependence of the magnetic susceptibility of xMnO · (1 − x)[70TeO2 · 25B2O3 · 5PbO] glasses with 0 <x ≤ 40 mol% have been investigated. The valence states and the distribution of manganese ions in the glass matrix depend on the concentration of these ions. We have established that in these glasses for x > 10 mol% both, Mn2+ and Mn3+ ions are present, which explains their magnetic behaviour.

Vitreous borate networks containing superstructural units: a challenge to the random network theory?

Borate glasses are an enigma in that there is now increasing evidence that their structures are dominated by superstructural units. Crystallographic data for a wide range of crystalline borates are used as a basis to propose a set of criteria for the formation of vitreous borate networks, taking into account the topological degrees of freedom necessary for conventional glass formation and using the PbOB2O3 system as an example. It is concluded that random network models of vitreous B2O3 containing large numbers of boroxol groups can be built with the correct density if they contain locally independent interpenetrating networks.