Phase formation and thermal stability of the compounds in the Bi2O3-PbO system

The scientific interest for the Bi₂O₃-PbO system has increased due to the importance of the PbO in the high-T _c superconducting phase formation in the Bi₂O₃-SrO-CaO-CuO system. Also Bi₂O₃-PbO system contains compounds with some specific semiconductor and dielectric properties and Bi₂O₃-based solid solutions are well known as high oxygen ion conductors.Previously, several low melting defined compounds have been identified in the system: 6Bi₂O₃·PbO; 3Bi₂O₃·2PbO; 4Bi₂O₃·5PbO; 4Bi₂O₃·6PbO and Bi₂O₃·3PbO.This work deals with the phase formation and thermal stability of these compounds. Under non-isothermal conditions, in all mixtures regardless of the Bi₂O₃/PbO ratio, the compound 6Bi₂O₃·PbO is preferentially formed, followed by the compound 4Bi₂O₃·5PbO. The formation of the compound 4Bi₂O₃·6PbO was not confirmed while the formation of the compound Bi₂O₃ 3PbO occurs through a complex mechanism which includes an intermediate step in which a solid solution with the litharge structure was identified. Under isothermal conditions in the same temperature range the tendency to form the stoichiometric compounds increases. All compounds form, decompose and melt at temperatures between 530–780°C.     

Thermal stability and crystallization kinetics of Pb and Bi borate-based glasses

Glasses with compositions 60B₂O₃–40PbO, 60B₂O₃–40Bi₂O₃, and 60B₂O₃–30Bi₂O₃–10PbO have been prepared and studied by differential thermal analysis. The crystallization kinetics of the glasses was investigated under non-isothermal conditions. From dependence of the glass transition temperature (T _g) on the heating rate, the activation energy for the glass transition was derived. Similarly the activation energy of the crystallization process was determined. Thermal stability of these glasses were achieved in terms of the characteristic temperatures, such as the glass transition temperature, T _g, the onset temperature of crystallization, T _in , the temperature corresponding to the maximum crystallization rate, T _p, beside the kinetic parameters, K(T _g) and K(T _p). The results revealed that the 60B₂O₃–40PbO is more stable than the others. The crystallization mechanism is characterized for glasses. The phases at which the glass crystallizes after the thermal process have been identified by X-ray diffraction.     

Effect of metal oxides on the gamma radiolysis of ammonium nitrate

The studies of radiation decomposition of ammonium nitrate in the presence of MnO₂, PbO and V₂O₅ with the absorbed dose reveal that MnO₂ retards while PbO and V₂O₅ accelerate the rate of radiolysis. G/NO ₂ ^– / values were found to increase with the mole% of V₂O₅ in an admixture. The results are explained on the basis of electron donor-acceptor properties of oxides affecting the equilibrium concentration of electrons present in pure ammonium nitrate in the presence of the added oxides.     

Critical assessment of the elemental composition of Corning archeological reference glasses by LA-ICP-MS

Corning archeological reference glasses A, B, C, and D have been made to simulate different historic technologies of glass production and are used as standards in historic glass investigations. In this work, nanoseconds (193, 266 nm) and femtosecond (800 nm) laser ablation were used to study the elemental composition of Corning glasses using laser ablation inductively coupled plasma mass spectrometry. The determined concentrations of 26 oxides (Li₂O, B₂O₃, Na₂O, MgO, Al₂O₃, SiO₂, P₂O₅, K₂O, CaO, TiO₂, V₂O₅, Cr₂O₃, MnO, Fe₂O₃, CoO, NiO, CuO, ZnO, Rb₂O, SrO, ZrO₂, SnO₂, Sb₂O₅, BaO, PbO, Bi₂O₃) are compared with values reported in the literature. Results show variable discrepancies between the data, with the largest differences found for Cr₂O₃ in Corning A; Li₂O, B₂O₃, and Cr₂O₃ in Corning B; and MnO, Sb₂O₅, Cr₂O₃, and Bi₂O₃ in Corning C. The best agreement between the measured and literature values was found for Corning D. However, even for this reference, glass re-evaluation of the data was necessary and new values for PbO, BaO, and Bi₂O₃ are proposed.     

Mechanism of formation ofo-semiquinone metal complexes under mechanical pulse action on metal oxide-quinone-pyrocatechol systems

The possibility of the mechanochemical synthesis of metal-containing mono-, bi-, and triradicals under mechanical pulse action on mixtures of metal oxides (CuO, ZnO, CdO, PbO, Al₂O₃, Ga₂O₃, Sb₂O₃, Bi₂O₃, Cr₂O₃, TiO₂, GeO₂, ZrO₂, or SnO₂) with quinone and pyrocatechol was examined. The reaction products are formed both on the surface of metal oxides and as individual solid phases. The mechanism of chemical processes that occur under the action of a single elastic wave pulse is proposed. Deceased. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 324–330, February, 1999.     

O2, CO2, and H2O Chemisorption on UN(001) Surface: Density Functional Theory Study

We performed density functional theory calculations of O₂, CO₂, and H₂O chemisorption on the UN(001) surface using the generalized gradient approximation and PW91 exchange-correlation functional at non-spin polarized level with the periodic slab model. Chemisorp-tion energies vs. molecular distance from UN(001) surface were optimized for four sym-metrical chemisorption sites. The results showed that the bridge parallel, hollow parallel and bridge hydrogen-up adsorption sites were the most stable site for O₂, CO₂, and H₂O molecular with chemisorption energies of 14.48, 4.492, and 5.85 kJ/mol, respectively. From the point of adsorbent (the UN(001) surface), interaction of O₂ with the UN(001) surface was of the maximum magnitude, then CO₂ and H₂O, indicating that these interactions were associated with structures of the adsorbate. O2 chemisorption caused N atoms on the surface to migrate into the bulk, however CO₂ and H₂O had a moderate and negligible effect on the surface, respectively. Calculated electronic density of states demonstrated the electronic charge transfer between s, p orbital in chemisorption molecular and U6d, U5f orbital.     

Chemisorption of SO2 and Cl2 on indium oxide

The mutual influence of SO₂ and Cl₂ during their consecutive chemisorption on the In₂O₃ surface has been investigated. It was found that SO₂ is chemisorbed in the uncharged form, and the amount of chemisorption decreases as the temperature increases. The preliminary chemisorption of Cl₂ results in a dramatic decrease in the amount of SO₂ sorbed and in a change in the character of the bonding of SO₂ with the oxide surface. When SO₂ is sorbed first, the temperature of the formation of chlorides during subsequent chemisorption of Cl₂ decreases.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1718–1721, October, 1994.     

ChemInform Abstract: High‐Temperature Behavior and Polymorphism in Novel Members of the Perovskite Family Pb2LnSbO6 (Ln: Ho,Er, Yb,Lu).

The title compounds are prepared by solid state reactions of PbO, Ln₂O₃, and Sb₂O₃ (1.     

The role of alkali content in the devitrification mechanisms of SiO2–Fe2O3–Na2O–PbO SYSTEM

Three batch compositions of pure oxides (SiO₂, Fe₂O₃, PbO, Na₂O) with equivalent SiO₂, Fe₂O₃ and PbO contents and a gradually increased Na₂O content were vitrified through heating in a high temperature electric furnace and subsequent quenching. The resulting vitreous products were thermally treated in order to study the devitrification behaviour, under conditions designated from differential thermal analysis experiments. Depending on the Na₂O content, crystal phase separation gave rise to the growth of acmite and hematite or maghemite. A uniformly phase separated glass-ceramic material, with crystallites of similar size and population density, was produced from devitrification of the vitreous product with the higher Na₂O content.     

Structural correlations in BaO–PbO–B2O3 glasses as inferred from FTIR spectra

Infrared spectra of xBaO·(30-x)PbO·70B₂O₃, xBaO·(40-x)PbO·60B₂O₃ and xBaO·(50-x)PbO·50B₂O₃ glasses have been quantitatively analyzed. The fraction of four coordinated boron atoms varies linearly, for each group, between the values of the corresponding binary borate glasses. The data could be used to calculate and follow the composition dependence of the concentration of structural units in all glasses. The results show a linear increase in the ratio of PbO forming BO₄ units to the total content of PbO, with increasing B₂O₃ in binary PbO–B₂O₃ glasses. Similar behavior has been observed for the ratio of BaO forming BO₄ units to the total content of BaO in binary BaO–B₂O₃ glasses. The ratio of PbO forming PbO₄ units to the total PbO content, and that of BaO forming asymmetric BO₃ units to the total BaO content, shows a reversed dependence. The linear change in fraction of four coordinated boron atoms and in density and molar volume suggests that the studied glasses can be treated as mixtures of binary PbO–B₂O₃ and BaO–B₂O₃ matrices.     

ChemInform Abstract: Formation and Stability of Gaseous Ternary Oxides of Group 14-16 Elements and Related Oxides of Group 15 Elements: Mass Spectrometric and Quantum Chemical Study.

The formation of the new compounds PbTeO₃, PbTe₂O₅, Pb₂TeO₄, and Pb₂Te₂O₆ is observed in the gas phase by heating a mixture of solid PbO and TeO₂ at 1063 K using a mass-spectrometric Knudsen-cell method.     

HgPb2O2Cl2, ein „perforiertes”︁ Blei(II)-oxid

HgPb₂O₂Cl₂, a “Perforated” Lead(II) Oxide Single crystals of HgPb₂O₂Cl₂ were grown in a HgCl₂ flux by reaction of PbO with HgCl₂. Crystal structure analysis by single crystal X-ray methods were carried out. HgPb₂O₂Cl₂ crystallizes monoclinic with a = 11.788(2) Å, b = 3.910(1) Å, c = 7.749(2) Å, β = 122.64(3)°, space group C2/m (No. 12) and Z = 2. HgPb₂O₂Cl₂ is the first member of a new structure type, closely related to the structure of PbO.     

Catalytic activity of solid solutions of nickelous and zinc oxides

Summary A comparison of the change in the rules of chemisorption of gas-acceptors and donors of electrons with catalytic activity for processes with gases of the same type showed that the change in the catalytic properties of NiO and ZnO and their solid solutions may be explained by the effect of dissolved oxides Li₂O, Ga₂O₃, Fe₂O₃, etc., on chemisorption. The change in chemisorption is considered to be connected with the effect of cations with an anomalous charge in the lattice points on the statistics of the active centers on the surface.     

Comparative studies in subsolidus areas of ternary oxide systems PbO–V2O5–In2O3 and PbO–V2O5–Fe2O3

Thermal stability of PbO was studied. Reactivity of oxides in the systems PbO–M₂O₃ (M = In, Fe) was investigated up to 650 °C. Using the DTA and XRD methods, parts of investigated ternary oxide systems, labelled by compounds: V₂O₅, Pb₈V₂O₁₃ and M₂O₃ (M = In, Fe), have been divided into partial ternary systems. IR spectra of compounds Pb₂MV₃O₁₁ (M = In, Fe) have been compared.     

Effect of the extent of reduction of V2O5 on the adsorption of propylene and the oxidative dehydrogenation of propane to give propylene on V2O5 and V2O5/TiO2-SiO2

An increase in the propylene output in the oxidative dehydration of propane on V₂O₅/TiO₂-SiO₂ was observed after prior reduction of V₂O₅ in the reaction mixture to V₂O₄, which reduces the destructive chemisorption of propylene. A low titanium dioxide content in TiO₂-SiO₂ hinders the deep reduction of V₂O₅ to V₂O₃, which reduces the conversion of propane. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 6, pp. 373–378, November–December, 2007.     

Die Vanadin-Koordination in den Phasen 4 PbO · V2O5 und 8 PbO · V2O5

Coordination of Vanadium in the Phases 4 PbO · V₂O₅ and 8 PbO · V₂O₅ It is demonstrated, using infrared spectroscopy, that the coordination of vanadium in the two binary phases 4 PbO · V₂O₅ and 8 PbO · V₂O₅ is tetrahedral. The spectra in the V? O stretching region closely resembles that of the lead(II) orthovanadate, Pb₃(VO₄)₂.     

Thermal analysis of pyrotechnical mixtures II

A two-component pyrotechnical mixture containing MnO₂ and Pb₃O₄ has been investigated by TG, DTG and DTA. It was found that under 48 % MnO₂ content the oxygen release exceeds the value calculated on the basis of the reactions MnO₂ → Mn₃O₄ and Pb₃O₄ → PbO. Above a MnO₂ content of 7.5 % the decomposition is partly delayed and shifted to higher temperatures. With under 60% of MnO₂, at about 700? the components react exothermally with an increase in weight. The combined heats of the reactions MnO₂ → Mn₂O₃ and Pb₃O₄ → PbO give the highest value at 83 % of MnO₂.     

Calorimetric study of the component steps of oscillating chemical reactions

An influence of inorganic compounds (Fe₂O₃, ZnO, PbO, CaCO₃ and K₂CO₃) on the blast furnace coke thermal oxidation in the air and in the CO₂atmosphere was investigated by means of thermal analysis. A catalytic effect showed itself at the oxidation in the air, especially with PbO and K₂CO₃. These compounds bring the oxidation starting temperature and activation energy down and increase the reaction rate constant most distinctly. The PbO and K₂CO₃ actions differ in their mechanisms. K₂CO₃ accelerates particularly the amorphous coke fractions oxidation. In the CO₂ atmosphere an important catalytic effect occurred only with K₂CO₃. The PbO catalytic influence is less distinct. This revised version was published online in July 2006 with corrections to the Cover Date.     

Radiolysis of quench-cooled pure and barium doped KNO3 in presence of oxides: Effect of particle size

Radiation decomposition studies of quenched pure KNO₃ and KNO₃ doped with Ba²⁺ ions in the presence of PbO or Al₂O₃ as a heterophase impurity showed that the yield of nitrite varied with the particle size of the nitrate. The G/NO ₂ ^– / values were also found to vary with the mol percent of PbO or Al₂O₃ in the mixture. Higher yields of nitrite were obtained in the presence of PbO, while in mixtures containing Al₂O₃, the yields of nitrite were lower in comparison with the G-values observed in the absence of oxide. These results are explained on the basis that a larger surface area results in an increased energy transfer at the interface between two neighbouring particles. The results can also be accounted for in terms of electron donor-acceptor properties of the added oxides.     

Contribution from the solid-phase interactions of activating oxides to their nonlinear joint effect on the thermal oxidation of GaAs

The contribution from the solid-phase interactions in the PbO + Sb₂O₃ and PbO + Bi₂O₃ activating compositions to the multichannel process of GaAs thermal oxidation has been determined by spatial separation of the oxides. The solid-phase interactions make a positive contribution to the overall negative nonlinear effect in the dependence of the oxide film thickness on the GaAs surface on the activator batch composition. The contributions from the oxide interactions on the semiconductor surface and in the gas phase have been evaluated for the PbO + Sb₂O₃ composition.