Tellurides acids

H2Se (hydrogen selenide, colorless), HSe (acid telluride ion, colorless), Se (selenide ion, colorless), H2Se03 (selenous acid, colorless), HSeOJ (acid selenite ion, colorless), SeO (selenite ion, colorless), H2Se04 (selenic acid, colorless), HSeOJ (acid selenate ion, colorless), SeO " (selenate ion, colorless). 

These two gases can readily be prepared by the action of acids on selenides and tellurides respectively, the reactions being analogous to that for the preparation of hydrogen sulphide. 

Tellurium improves the machinability of copper and stainless steel, and its addition to lead decreases the corrosive action of sulfuric acid on lead and improves its strength and hardness. Tellurium is used as a basic ingredient in blasting caps, and is added to cast iron for chill control. Tellurium is used in ceramics. Bismuth telluride has been used in thermoelectric devices. 

Heavy water, see Hydrogen[ H] oxide Heazlewoodite, see rn-Nickel disulfide Hematite, see Iron(III) oxide Hermannite, see Manganese silicate Hessite, see Silver telluride Hieratite, see Potassium hexafluorosilicate Hydroazoic acid, see Hydrogen azide Hydrophilite, see Calcium chloride Hydrosulfite, see Sodium dithionate(III)... 

The polar tellurium(II)-nitrogen bond is readily susceptible to protolysis by weakly acidic reagents. Eor example, the reaction of [Te(NMe2)2]oo with two equivalents of Ph3CSH produces the monomeric thiolato derivative Te(SCPh3)2. Alkynyl tellurides may be prepared by the reaction of terminal acetylenes with arenetellurenamides (Eq. 10.13). ... 

Most selenides and tellurides are decomposed by water or dilute acid to form H2Se or H2Te but the yields, particularly of the latter, are poor. 

Tellur-sfiure, /. telluric acid, -schwefelkohlen-stoff, m. carbon sulfide telluride, CSTe. -sil-ber, n. silver telluride. -silberblei, n. lead silver telluride, Min.) sylvanite. -silber-blende,/. sylvanite stutzite. 

Tellur-verbindung, /. tellurium compound, -vorlegierung,/. tellurium prealloy, -wasser-stoff, m. hydrogen telluride. -wasserstoff-sSure, /. hydrotelluric acid (hydrogen telluride). -wismut, n. bismuth telluride. 

Molybdenum hexafluoride. 3,1412 Molybdenum-iron-sulfur complexes, 4,241 Molybdenum oxide amino acid formation prebiotic systems, 6, 872 Molybdenum storage protein microorganisms, 6, 681 Molybdenum telluride, 3, 1431 Molybdenum tetraalkoxides physical properties, 2, 347 Molybdenum tribromide, 3,1330 Molybdenum trichloride, 3,1330 Molybdenum trifluoride, 3, 1330 Molybdenum trihalides, 3, 1330 bond lengths, 3, 1330 magnetic moments, 3,1330 preparation, 3,1330 properties, 3, 1330 structure, 3,1330 Molybdenum triiodide, 3,1330 Molybdenum trioxide complexes, 3, 1379 Molybdenum triselenide, 3, 143)... 

Selenic acid, H2Se04, is a strong acid (/fai 2) and the solubility of its salts parallels that of the corresponding sulfates. It is formed by the oxidation of selenous acid or elemental selenium with strong oxidizing agents in the presence of water. Telluric acid, H2Te04, or tellurates are obtained by oxidation of tellurides,... 

H2Te (hydrogen telluride, colorless), HTe (hydrogen telluride ion, colorless), Te (telluride ion, colorless), Te (ditelluride ion, red), Te" + (tellurous ion), HTeOj (telluryl ion), HTeO (acid tellurite ion, colorless), TeO " (tellurite ion, colorless), H2Te04 (telluric acid, colorless), HTeOJ (acid tellurate ion, colorless), TeO (tellurate ion, colorless). 

The induced co-deposition concept has been successfully exemplified in the formation of metal selenides and tellurides (sulfur has a different behavior) by a chalcogen ion diffusion-limited process, carried out typically in acidic aqueous solutions of oxochalcogenide species containing quadrivalent selenium or tellurium and metal salts with the metal normally in its highest valence state. This is rather the earliest and most studied method for electrodeposition of compound semiconductors [1]. For MX deposition, a simple (4H-2)e reduction process may be considered to describe the overall reaction at the cathode, as for example in... 

Fig. 3.5 Potential vs. pH diagram for the CdTe-H20 system at 25 °C. Solid CdTe is thermodynamically stable over the entire pH range. Consequently, CdTe does not hydrolyze at any H and OH activities of practical interest. In acidic solutions, the only process accompanying cathodic CdTe polarization is hydrogen release. Therefore, in the region of cathode potentials, CdTe is a sufficiently stable electrode material from the electrochemical point of view. The -1.35 V potential is the lowest limit of stabihty. Below this limit, CdTe corrodes in the whole pH range e.g., for pH < 2.8, H2Te vapor is produced at -1.25 V. For pH > 2.8, diteUuride or telluride ions are formed with disintegration of the compound. (With kind permission from Springer Science+Business Media [82])...

The electrodeposition of tellurium and silver has been investigated in dilute aqueous solutions of tellurous acid and Ag " ions (concentrations in the order of 10 to 10 " M) in 0.1 M HCIO4 [164], In particular, cyclic voltammetry experiments were conducted with rotating glassy carbon disk electrodes in baths with various concentration ratios of Ag(I) and Te(IV) precursors, and their outcome was discussed in terms of the voltammetric features. For a Ag(I)/Te(IV) ratio close to 0.8, formation of quasi pure silver telluride, Ag2Te, was reported. The authors, based on their measurements and on account of thermodynamic predictions, assumed that silver is deposited first on the electrode (Ag" + e Ag), and then Te(IV) is reduced on the previous silver deposit with formation of Ag2Te according to the reaction... 

Cathodic deposition of bismuth(in) telluride films has been reported [224] also on copper and nickel foils, from aqueous nitric acid solutions of bismuth oxide and tellurium oxide in molar ratios of Bi Te = 3 3 and 4 3, at 298 K. The... 

Similar to PbSe, the controlled growth of lead telluride, PbTe, on (111) InP was demonstrated from aqueous, acidic solutions of Pb(II) and Cd(II) nitrate salts and tellurite, at room temperature [13]. The poor epitaxy observed, due to the presence of polycrystalline material, was attributed to the existence of a large lattice mismatch between PbTe and InP (9%) compared to the PbSe/InP system (4.4%). The characterization techniques revealed the absence of planar defects in the PbTe structure, like stacking faults or microtwins, in contrast to II-VI chalcogenides like CdSe. This was related to electronic and structural anomalies. 

A similar procedure has been used to cathodically deposit lead telluride, PbTe, onto n-Si(lOO) wafers from an acidic electrolyte containing Pb(ll) and Te(IV) species at ambient conditions [106], Rock salt PbTe particles with size from 80 to 180 nm were obtained, distributed randomly on the Si substrate. The mechanism of PbTe nucleation was considered to involve OPD of 3D islands of tellurium followed by lead UPD. The barrier for anodic current formed at the n-Si/PbTe interface rendered the deposition of PbTe irreversible, although high-efficiency photooxidation... 

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