As and Sb

Some crystalline compounds formed by AS2O3 with alkali and ammonium halides, for example, NH4CI.AS2O3. H2O, KCl. 2 AS2O3, etc., are closely related structurally to arsenious oxide. In the former, there are hexagonal AS2O3 sheets, with all O atoms directed to one side of the sheet, arranged in pairs with the 

0 atoms turned toward each other and with water molecules enclosed between the layers. Between these pairs of AS2O3 layers there are NH4 and Cl ions. 

Bismuth forms with other metallic oxides an extraordinary variety of complex oxides, in some of which 0 can be replaced by F. 

The systems Ca(Sr, Ba, Cd, Pb)0-Bi203. Studies have been made of some of the phases formed when Bi203 is fused with one of the oxides CaO. SrO, BaO, CdO, or PbO. The phases studied show variation in composition over rather wide ranges. For example, in the system BaO—Bi203 there is a rhombohedral phase (x = 0 10-0-22) and a tetragonal phase (x = 0-22-0-50), where x is the atomic fraction of Ba in Ba2 eBi2 2 e03 . Structures have been proposed for a number of such phases, in which it is concluded that the metal content of the unit cell is constant but the oxygen content variable. 

X-ray studies have also been made of a series of complex oxides with tetragonal or pseudotetragonal symmetry which all have the a dimension of the unit cell close to 3-8 A, and are based on sequences of Bi202 layers of the same type as in Fig. 20.6, interleaved with portions of perovskite-like structure. They are summarized in Table 20.5. and illustrated in Fig. 20.5. The simplest member of the family is at present represented only by compounds in which part of the 0 is replaced by F. 

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Theoretical studies of diffusion aim to predict the distribution profile of an exposed substrate given the known process parameters of concentration, temperature, crystal orientation, dopant properties, etc. On an atomic level, diffusion of a dopant in a siUcon crystal is caused by the movement of the introduced element that is allowed by the available vacancies or defects in the crystal. Both host atoms and impurity atoms can enter vacancies. Movement of a host atom from one lattice site to a vacancy is called self-diffusion. The same movement by a dopant is called impurity diffusion. If an atom does not form a covalent bond with siUcon, the atom can occupy in interstitial site and then subsequently displace a lattice-site atom. This latter movement is beheved to be the dominant mechanism for diffusion of the common dopant atoms, P, B, As, and Sb (26). 

In either case the Pb contains numerous undesirable metal impurities, notably Cu, Ag, Au, Zn, Sn, As and Sb, some of which are clearly valuable in themselves. Copper is first removed by liquation the Pb bullion is melted and held just above its freezing point when Cu rises to the surface as an insoluble solid which is skimmed off. Tin, As and Sb are next removed by preferential oxidation in a reverberatory furnace and skimming off the oxides alternatively, the molten bullion is churned with an oxidizing flux of molten NaOH/NaN03 (Harris process). The softened Pb may still contain Ag, Au and perhaps Bi. Removal of the first two depends on their preferential solubility in Zn the mixed metals are cooled slowly from 480° to below 420° when the Zn (now containing nearly all the Ag and Au) solidifies as a crust which is skimmed off the... 

Despite this, they are good solvents for chloride-ion transfer reactions, and solvo-acid-solvo-base reactions (p. 827) can be followed conductimetri-cally, voltametrically or by use of coloured indicators. As expected from their constitution, the trihalides of As and Sb are only feeble electron-pair donors (p. 198) but they have marked acceptor properties, particularly towards halide ions (p. 564) and amines. 

Boron enflames in contact with IF3 so do P, As and Sb. Molybdenum and W enflame when heated and the alkali metals react violently. KH and CaC2 become incandescent in hot IF3. However, reaction is more sedate with many other metals and non-metals, and compounds such as CaCOs and Ca3(P04)2 appear not to react with the liquid. 

Since about 1970 there has been very little activity in the whole field of aryl-element chemistry as fas as arenediazonium ions are involved. The activity on As- and Sb-organic compounds early in this century was probably stimulated by the discovery of Salvarsan (3,3 -diamino-4-4 -dihydroxy-arsenobenzene) by Paul Ehrlich in 1909. In spite of the epoch-making success of this first chemotherapeutic drug, it... 

Under aerobic conditions, S -adenosyhnethionine is the methyl donor for methylation of meth-anethiol and methaneselenol (Drotar et al. 1987), and probably for the bacterial methylation of halogenated phenols and thiophenols (Neilson et al. 1988). It is also the probable methyl donor for fungal methylation of the oxyanions of As and Sb (Bentley and Chasteen 2002). 

Chemical analytical data are summarized in Table 2.13 and Table 2.14. The back-arc deposits are characterized by higher Pb, Ba Ag, Au, As and Sb contents than midoceanic ridge deposits. This difference is due to different mineralogy which is described below. 

Bulk compositions of midoceanic ridge deposits and back-arc deposits are summarized in Tables 2.16 and 2.17. It is clear that midoceanic ridge ores contain higher amounts of Fe, Mn, Zn, Co, Ni, Se and Pt but lower amounts of Au, Ag, Cu, Pb, Ba, As and Sb compared with back-arc deposits (Tables 2.18 and 2.19). 

This reaction means that higher /hjS causes higher concentration of Au(HS)2 as well as higher fo. Higher fujS, /ss and /o, of back-arc hydrothermal fluids can explain higher Au, Hg, As and Sb who.se dominant dissolved species are probably thio complexes. 

Feliu JM, Femhidez-Vega A, Aldaz A, Clavilier J. 1988. New observation of a structure sensitive electrochemical behaviour of irreversibly adsorbed As and Sb from acidic solution on Pt(lll) and Pt(lOO) orientations. J Electroanal Chem 256 149-163. 

Phosphorus is the most common donor atom in Ni° chemistry. Likewise, As- and Sb-based ligands are well suited for stabilizing low-valent Ni°. Ni° phosphine chemistry is extensive, and the general synthetic approaches have been summarized previously. 

Heterocyclic phosphines 32 were prepared from base-induced condensation of a secondary 1,8-diamino-naphthalene with phosphorus trichloride (the corresponding As- and Sb-analogues were obtained analogously) and converted into cyclic phosphenium cations 33 by Lewis acid promoted halide abstraction using GaCl3 or trimethylsilyl triflate as reagents (Scheme 18) [15, 92],... 

At present, the elements used in the formation of compounds by EC-ALE include the chalcogenides S, Se, and Te the pnictides As and Sb the group three metals Ga and In the group II metals Zn, Cd, and Hg as well as Cu, and Co. The range of compounds accessible by EC-ALE is not clear. The majority of work has been performed on II VI compounds (Table 1). The III-V compounds InAs and InSb have recently been formed, and the first deposits of a III-VI compound, InSe, have been made [151], In addition, Shannon et al. have begun studies of CoSb [152] with the intent of forming thermoelectric materials. 

All of the elements are important, and they are found in many common compounds. Some phosphorus compounds are among the most useful and essential of any element. As a result, there is a great deal more extensive chemistry of phosphorus, and more space will be devoted to it in this chapter. Much of the chemistry of the other elements can be inferred by comparison to the analogous phosphorus compounds but realizing the greater metallic character of As and Sb. 

Fig. 9. IR absorption bands in P-, As-, and Sb-doped Si samples that had been passivated in an H2 plasma. The sharp bands to the left are assigned to H-stretching modes of the donor-H complexes. The spectra were recorded near liquid He temperature. [Reprinted with permission from The American Physical Society, Bergman, K., Stavola, M., Pearton, S.J., Lopata, J. (1988), Phys, Rev. B 37, 2770.]... 

Frequencies, linewidths, and relative intensities for the absorption bands of P, As, and Sb... 

Emissions from B02 [103], AsO, and SbO [103, 104] in an FPD flame have been used to detect organics or highly reduced species containing B, As, and Sb, respectively. These metal atoms react to form the same excited-state metal oxides discussed in their reactions with ozone above. These analytes have limits of detection measured to be approximately 50 ppbv, 10 ppbv, and 20 ppbv, respectively [93],... 

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