Red PbO Research Articles

Coherent view of crystal chemistry and ab initio analyses of Pb(II) and Bi(III) lone pair in square planar coordination

The stereochemistry of 6s2 (E) lone pair of divalent Pb and trivalent Bi (PbII and BiIII designated by M*) in structurally related PbO, PbFX (X= Cl, Br, I), BiOX (X= F, Cl, Br, I) and Bi2NbO5F is rationalized. The lone pair LP presence determined by its sphere of influence E, equal to those of oxygen or fluorine anions, was settled by its center then giving M*-E directions and distances. Detailed description of structural features of both elements in the title compounds characterized by [PbEO]n and [BiEO]n layers allowed to show the evolution of M*-E distance versus the changes with the square pyramidal SP coordination polyhedra. All are different, in red PbO one finds {PbEO4E4} square antiprism, a {[Bi.E]O4X4Xapical} monocapped square antiprism in PbFX and BiOX and {BiEO4F4}square antiprism in Bi2NbO5F. To analyze the crystal chemistry results, the electronic structures of these compounds were calculated within density functional theory DFT. Real space analyses of electron localization illustrate a full volume development of the lone pair on PbII within {PbEO4E4} in PbOE, {PbEF4X4} in PbFXE and Bi(III) within {BiEO4X4} square antiprisms, contrary to Bi(III) within {[Bi.E]O4F4Fapical} monocapped square antiprism. Larger hardness (larger bulk modules B0) and band gap characterize BiOF versus PbO due to the presence of F which brings antibonding Bi-F interactions oppositely to mainly bonding Bi-O. In PbFX and BiOX series there is a systematic decrease of B0 with the increasing volume following the nature and size of X which is decreasingly electronegative and increasingly large. The electronic densities of states mirror these effects through the relative energy position and relative electronegativities of F/X and O/X leading to decrease the band gap.

Four New Lead(II) Thiolate Cluster Complexes – Unexpected Products of a Conventional Synthesis

AbstractThe reaction of Pb(OOCCH3)2·3H2O with 2.1 equiv. of HS‐2,6‐(CH3)2C6H3 in ethanol/water is expected to give [Pb{S‐2,6‐(CH3)2C6H3}2]. However, we obtained an orange powder whose elemental analysis disagrees with that of the expected product and indicates small amounts of oxygen. Layering of concentrated solutions of this orange powder in dry THF with pentane under nitrogen results in the formation of a mixture of three identifiable crystalline compounds, namely [Pb10{S‐2,6‐(CH3)2C6H3}20], [Pb6S{S‐2,6‐(CH3)2C6H3}10(C4H8O)4] and [Pb8O2{S‐2,6‐(CH3)2C6H3}12]. In contrast, fractional crystallization from dilute solutions initially yielded only yellow crystals of [Pb14O6{S‐2,6‐(CH3)2C6H3}16]. Further concentration of the supernatant solution yielded, upon layering with pentane, [Pb6S{S‐2,6‐(CH3)2C6H3}10(C4H8O)4] and [Pb10{S‐2,6‐(CH3)2C6H3}20], which are almost completely separable by controlling the duration of the crystallization step and the amount of condensed pentane. Recrystallization of the crude orange powder under aerobic conditions produces pure [Pb14O6{S‐2,6‐(CH3)2C6H3}16] with a yield five times higher than that under nitrogen. This shows that it is sensitive to oxidation by oxygen in solution. The structures of all four complexes have been determined by single‐crystal X‐ray analysis. The net formed by the six oxygen and twelve lead atoms in the center of [Pb14O6{S‐2,6‐(CH3)2C6H3}16] resembles a small piece of a layer of the solid‐state structure of red PbO. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Thermal evolution and crystal structure of a polymeric complex: Pb 3(3,5-dicarboxylatopyrazole) 2(NO 3) 2·4H 2O

Pb 3(pdc) 2(NO 3) 2·4H 2O (pdc=deprotonated 3,5-pyrazole-dicarboxylic acid) has been prepared and is stable up to 100 °C. Above this temperature the hydration water loss is noted before 200 °C. Until 360 °C the material becomes amorphous during the decomposition of the organic ligand; at 365 °C crystallization occurs and can be formulated as a mixture of PbO and lead oxynitrates, which subsequently recombines between 395 and 445 °C into Pb 6O 5(NO 3) 2 over 570 °C, the residue is essentially red PbO. Pb 3(pdc) 2(NO 3) 2·4H 2O crystallizes in the monoclinic system, a=20.3688(7), b=6.4232(4), and c=18.1059(7) Å, β=118.44(1)°, space group C2/ c, Z=4. The structure displays an original polymeric coordination complex where the lead(II) is found in two different environments: (–Pb2–pdc–) ∞ chains are identified along the [001] direction, while inter chains Pb2–pdc and Pb1–pdc links are bridging these chains in a layer like tridimensionnal structure, where pdc is acting as an hexadentate ligand.

The structure of lead-silicate glasses: molecular dynamics and EXAFS studies

Molecular dynamics (MD) simulations and extended x-ray absorption fine structure (EXAFS) investigations of the structure of lead-silicate glasses, xPbO(1 − x)SiO2, have been undertaken to elucidate the problem of partially contradicting experimental findings reported in the literature about basic structural units and their interconnection. The MD simulations were performed in a wide range of compositions, x = 0.1–0.9. The atoms were assumed to interact by a two-body Born–Mayer–Huggins interaction potential. The EXAFS measurements were performed for x = 0.3, 0.5 and 0.7, and also for pure crystalline (red) PbO at the L3-edge of Pb. The absorption spectra were analysed within the GNXAS approach.Our EXAFS and MD results are in good agreement, and support some previous suggestions that: (1) the PbO4 groups are the dominant structural units in lead-silicate glasses for any concentration and (2) at lower PbO concentrations the co-existence of the PbO4 and PbO3 groups is possible.The medium-range ordering in the simulated glasses has also been investigated in detail. The connectivity of the SiO4 tetrahedra network breaks at about x = 0.45, whereas the Pb structural units form a continuous (mainly edge-sharing) network even at relatively low PbO concentrations (x > 0.2). The cation–anion ring statistics is also discussed.

Solid-State Synthesis of Ferroelectric Lead Metatantalate

Lead metatantalate was prepared by solid-state reactions in the PbO–Ta2O5and PbCO3–Ta2O5systems. The process was followed by differential thermal analysis and x-ray diffraction. The solid-state synthesis of PbTa2O6was found to proceed through the formation of the cubic pyrochlore phase 3PbO · 2Ta2O5 . The red PbO resulting from PbCO3decomposition is more reactive with Ta2O5as compared to yellow PbO. As a result, during continuous heating, the ferroelectric phase of PbTa2O6forms at a 50°C lower temperature.

Influence of hydrogen reduction on the structure of PbSiO 3 glass: an EXAFS study

A new X-ray analysis of the structure of lead-silicate glass PbSiO 3, and of its hydrogen-reduced form, is presented. The X-ray absorption spectroscopy (XAS) experiments were performed at the L 3-edge of Pb, and the data have been analyzed in the framework of the multiple scattering (MS) theory. The influence of the reduction time on the glass structure is presented. In unreduced glass the Pb atom neighborhood resembles the corresponding local ordering in red PbO. On increasing the reduction time Pb neighborhood becomes more and more similar to that of fcc lead, which is compatible with the experimentally observed creation of metallic lead granules.

The high-temperature thermal expansion of BiPbSrCaCuO superconductor and the oxide components (Bi2O3, PbO, CaO, CuO)

The thermal expansion of superconducting Bi1.6Pb0.4Sr2Ca2Cu3Ox (BiPbSrCaCuO) and its oxide components Bi2O3, PbO, CaO and CuO have been studied by high-temperature dilatometric measurements (30–800°C). The thermal expansion coefficient for the BiPbSrCaCuO superconductor in the range 150–830°C is α=6.4×10−6K−1. The temperature dependences of ΔL/L of pressed Bi2O3 reveals sharp changes of length on heating (T1=712°C), and on cooling (T2=637°C and T3=577°C), caused by the phase transition monoclinic-cubic (T1) and by reverse transitions via a metastable phase (T2 and T3). By thermal expansion measurements of melted Bi2O3 it is shown that hysteresis in the forward and the reverse phase transitions may be partly caused by grain boundary effect in pressed Bi2O3. The thermal expansion of red PbO reveals a sharp decrease in ΔL/L, on heating (T1=490°C), related with the phase transition of tetragonal (red, a=0.3962 nm, c=0.5025 nm)-orthorhombic (yellow, a=0.5489 nm, b=0.4756 nm, c=0.5895 nm). The possible causes of irreversibility of the phase transition in PbO are discussed. In the range 50–740°C the coefficient of thermal expansion of pressed Bi2O3 (αm=3.6 × 10−6 and αc=16.6×10−6K−1 for monoclinic and cubic Bi2O3 respectively), the melted Bi2O3 (αm=7.6×10−6 and αc=11.5×10−6K−1), PbO (αt=9.4×106 and ωor=3.3×10−6K−1 for tetragonal and orthorhombic PbO respectively), CaO (α=6.1×10−6K−1) and CuO (α=4.3×10−6K−1) are presented.

An original oxide of antimony and tungsten related to aurivillius phases

Aurivillius 's phases exhibit original [Bi 2O 2] n layers; up to now such phases exist only with bismuth. The aim of this paper is to report new related phase, containing only antimony, which is promissing because its ferroelastic properties. Synthesis, crystal growth and structure determination of the original double oxide Sb 2WO 6 has been performed. It crystallizes in the triclinic system, space group P1, with a=5.554(1), b=4.941(2), c=9.209(3) A ̊ , α=90.05(3), β=96.98(2), γ=90.20(2)°, V=250.8(7) A ̊ 3 . TEM and optical microscopy investigations allow to evidence a ferroelastic behaviour at room temperature with a phase transition in the range 300–400°C. The crystal structure of Sb 2WO 6 is built up by [WO 4] n layers of WO 6 octahedra sharing corners sandwiched by two [Sb 2O 2] n layers; it can be described as [WO 2Sb 2O 4] n thick layers held together by weak Sb...O interactions. The antimony atoms exhibit typical 3+1 one sided coordination. Via structural relationships with Sb 2O 3, VOSb 2O 4 and Bi 2WO 6, Sb 2WO 6 is related with the Aurivillius phases announcing how [Bi 2O 2] n layers with the shape encountered in red PbO can be formed or distorted.

The crystal structures of PbO.PbXO 4 (X = S, Cr, Mo) at 5K by neutron powder profile refinement

The structures of PbO.PbXO 4 monobasic lead oxide- lead sulphate, chromate and molybdate have been determined at 5K by neutron powder profile refinement. They are all isostructural with Lanarkite (the sulphate), being based on the red PbO structure with PbO 2 2− and its lone pair electrons replaced by XO 4 2−. A similar mechanism apparently produces the di-basic and tetra-basic oxides nPbO.PbXO 4. These materials are of relevence to solid state reactions in lead — acid battery electrodes.

Analytical investigations of the nonstoichiometry of lead zirconate and lead titanate. Lattice parameters of solid solutions of TiO 2 in red PbO

Lead titanate and lead zirconate containing either excess PbO or excess TiO 2 resp. ZrO 2 were treated with acetic acid and with hydrochlorid acid, and the solubility was studied. It was established, that the analytical results were dependent on the stoichiometry of the perovskit phase. Based on solubility differences the non-stoichiometry of lead titante and of lead zirconate were quantitatively determined at 400 – 800 °C. The lattice parameters of red PbO, a and c, have been shown to fall, if PbO takes up TiO 2 as a solid solution.

Oxides formed on the (111) surface of lead II. Red PbO or litharge

The electron microscopy of oxidized lead films revealed that the oxide consists of a yellow PbO layer in which small (10 −17−10 −18 cm 3) rectangular islands of red PbO are dispersed. The red PbO islands are thicker than the yellow PbO layer and are oriented with their [0 21] direction approximately perpendicular to the (111) surface of the lead film. Moiré fringe patterns visible in the red PbO islands show that their lattices are bent. The magnitude and sign of this bendings was measured. It was found that the bending enables the red PbO islands to satisfy one epitaxial orientation near their center and two forms of another near their ends. However, the bending does not arise entirely from an attempt to satisfy two epitaxial relationships simultaneously. The bending seems to result promaroly from a gradient in the oxygen concentration. As this gradient is unlikely to be constant it is probable that a true elastic strain is also present. Simple explanations for the sign of the lattice bending and for the shape and orientation of the red PbO grains are proposed.

Oxides formed on the (111) surface of lead I: Orthorhombic PbO or massicot

The structure of oxide films formed on the (111) surface of polycrystalline but highly textured lead films was determined by transmission electron microscopy and diffraction. It was found that most of the lead surface was covered by a thin layer of yellow orthorhombic PbO or massicot. The yellow PbO grains were small compared with those of lead and tended to be oriented with their (001) plane parallel to the (111) surface of lead. There was also a tendency for the (010) plane of PbO to be parallel to one of the three { 1 10} lead planes that were perpendicular to the specimen plane. The preference for this orientation relationship is a little surprising. This is because there are orientation relationships that lead to a small misfit between lead and yellow lead oxide but this is not one of them. A small fraction of the lead surface was covered by small grains of red tetragonal PbO or litharge.

Grinding Effects on PbO and Pb3O4-Synthesis of Basic Lead Carbonate by Grinding and Photoconductivity of the Ground PbO

Phase transformation of yellow orthorhombic PbO to red tetragonal form was confirmed by grinding at room temperature. The long time grinding in atmosphere converted the PbO powder into white lead, the basic lead carbonate, Pb3(CO3)2(OH)2 finally. The first reaction product in the nitrogen stream was not white lead, but lead oxy-carbonate, PbO. PbCO3. Thus the effect of moisture was prevented well in this condition, though the carbonate formation was not avoided.The line profiles of the X-ray powder diffration patterns of the ground product are fairly sharp. The average size of the crystallites determined by the line breadths is about 200Å in diameter, and this value agrees well with that of the electron microphotograph.The density of the white lead thus obtained is rather high compared with the ordinary one. The sharp line profiles must be due to the crystallization by constant grinding. Consequently it may be assumed that a quasiequilibrium state is established between the decomposition and the formation of white lead crystallites.Pb3(CO3)2(OH)2_??_Decomposition by grindingH2O+CO2X-ray amorphous PbOWhen the Pb3O4 is converted into a mixture of white lead and α-PbO2 by grinding in atmosphere the product turns dark brown.The photoconductivity measurement of the ground samples was carried out at their early stage of grinding in their visible and near infra-red region. Two new peaks appeared at 680mμ and 950mμ. The peak at 680mμ was largely affected by moisture and in some cases this peak was very high and overlapped the second lower 950mμ peak. The 680mμ peak will be attributed to the absorption of water molecules on the active site of the PbO surface, and the 950mμ peak to some lattice imperfection originated by grinding on the surface region of the PbO grains, respectively.The synthetic reaction of basic lead carbonate by grinding red PbO is explained on the basis of “active states” that appeared in the PbO grains by grinding.

Influence of impurities on the formation of red and yellow PbO

The influence of silica and other impurities, as well as of reactant concentrations, upon the course of the reaction between lead acetate and ammonium hydroxide, and upon the identity of the reaction products, are described. The immediate reaction product is a white precipitate consisting of either Pb(CH 3COO) 2·2Pb(OH) 2, or Pb(OH) 2, or a mixture of these compounds, depending upon the presence or absence of impurities, and upon reactant concentrations. In contact with the supernatant liquid the basic acetate or hydroxide converts spontaneously into a green precipitate which has the orthorhombic structure of yellow lead oxide. After decantation and drying the result is red, tetragonal lead oxide if certain impurities are absent. The elements Si, Ge, P, As, Sb, Se, Te, Mo and W, when present in the precipitation solution as anions at concentrations as low as 10–100 ppm prevent the transformation of the orthorhombic into the tetragonal structure. The result is then yellow orthorhombic lead oxide. By application of these findings, it is possible to prepare ultra-pure red oxide, or the yellow oxide only slightly contaminated with one of the specified elements, as desired.

Quantum efficiency of photoconduction in lead oxide

The quantum efficiency of the photoconduction of crystals of red PbO with an aqueous electrode is unity in the wavelength region between 3800 and 3100–3500 Å. This offers a means of calibrating the intensity of mercury lamps emitting at 365/6 mμ.

The preparation of ultra pure lead oxide

A method is described for preparing very pure PbO from lead acetate with ammonia at room temperature. Preparation in polyethylene vessels gives red PbO, which contains 1 ppm. silica and about 10 ppm. carbon. As more than 20 ppm. Si prevent the spontaneous recrystallisation in water from yellow orthorhombic to red tetragonal PbO, preparation in silica vessels gives yellow PbO, which contains 100 ppm. silica and 1000 ppm. carbon. Results of spectrochemical and mass spectrometric analysis are included.

The bonding in red PbO

The bonding in red PbO is elucidated. As in yellow PbO, the oxygen electrons are used entirely in the intra layer bonding. Oxygens are most probably hybridized sp 3 and are in van der Waals contact with one another in the layer. Lead forms four equivalent bonds to the four nearest oxygens using hybrids containing two 6 p orbitals, the 6 d x 2 − y 2 orbital and part of both the 6 s and the other 6 p orbital. The remainders of the 6 s orbital and the 6 p orbital are used to form a hybrid orbital containing the lone pair of electrons. These lone pairs are directed towards the next layer and hold adjacent layers together by van der Waals forces.

On the crystal structure of tetragonal (red) PbO

On the crystal structure of tetragonal (red) PbO