Sulfides electrical properties

The structural chemistry of the actinides is often similar to that of lighter transition metals, such as Zr and Hf, and to that of the lanthanides however, the diffuse nature of the 5/ orbitals leads to some differences and specifically to interesting magnetic and electrical properties. The actinide sulfides are generally isostructural with the selenides, but not with the analogous tellurides. The binary chalcogenides of uranium and thorium have been discussed in detail [66], but the structural... 

Mane, R. S. Lokhande, C. D. 2003. Studies on structural, optical and electrical properties of indium sulfide thin films. Mater. Chem. Phys. 78 15-17. 

RYTON Polyphenylene sulfide Physical, Chemical, Thermal, and Electrical Properties, TSM-266, Phillips Chemical Co., Bartlesville, Okla., Apr. 1981, p. 2. 

It should not be supposed that crystal defects enter into the picture only as nuisances which the chemist seeks to avoid or eliminate. Actually, certain optical and electrical properties of oxides, sulfides, and halides have been found to depend strongly on the nature and extent of crystal defects. Indeed, semiconductivity, fluorescence (absorption of radiation and emission of less energetic radiation), and phosphorescence (delayed fluorescence) of some salts may be spectacularly increased, not only by a small stoichiometric excess of one of the constituents, but also by addition of very tiny quantities of a foreign ion. Perhaps the best known example is the case of zinc sulfide which, when precipitated from aqueous solution and dried at low temperatures, shows negligible fluorescence upon exposure to ultraviolet light. When the sulfide is heated to... 

The sulfides have been studied much less than the oxides, but it is clear that many similarities exist. Like the oxides, a number of stable phases exist and nonstoichiometry is prevalent. The most important sulfide is TiS2, which has the Cdl2 layer structure, in which the Ti atoms occupy octahedral sites between alternate layers of close-packed sulfur atoms. The adjacent sulfur layers are able to intercalate Lewis bases such as aliphatic amines. Similar intercalation compounds can be made with MS2 and MSe2 compounds (M = Ti, Zr, Hf, V, Nb, Ta). Many of these compounds exhibit useful electrical properties including superconductivity see Superconductivity). 

The monosulfides of the rare earth elements behave differently from that discussed here since these are metal-like for all but those elements forming the most stable divalent states. Here a general proclivity towards forming tripositive ions seems more important (as in the metals themselves)—a property usually considered to result from a fortuitous balance between ionization and lattice or solvation energies. The sulfides have also been interpreted in terms of a degeneracy of the upper 4f levels with a 5d band (where applicable) (10). In contrast to the halides, there is little differentiation of the electrical properties among the monosulfides, monoselenides, and monotellurides (29). 

Although this theory explains theoretically the experimental observations in the case of ReOj, TiO, and VO, it fails to verify the conductivity characteristics of transition metal oxides such as TiO, VO, MnO, and NiO. Band theory explains the metallic characteristics but fails to account for the electrical properties of insulators or semiconductors and metal-nonmetal transitions because of neglect of electronic correlation inherent in the one-electron approach to the problem. Although there is no universal model for description of the conductivity, magnetic and optical properties of a wide range of materials (e.g., simple and complex oxides, sulfides, phosphides), several models have been proposed (for details, see Refs. 447-453). Of these, a generally accepted one is that described by Goodenough (451). 

The electrical properties of the three polyphenylene sulfide compounds are given In Table IV. The 40% glass-filled PPS Is the best Insulator as Indicated by the dielectric constant of 3.8. 

Table V Indicates the good retention of electrical properties exhibited by the 40% glass-filled PPS at temperatures up to 147°C. In addition, exposure of test specimens to 50 per cent relative humidity for 5 days did not cause any appreciable change In either dielectric constant or dissipation factor. Thus, environmental factors do not have much effect upon the electrical behavior of polyphenylene sulfide resins.

Electrical properties of polyphenylene sulfide compounds are summarized in Table III. The dielectric constant of 3.1 is low in comparison with many other plastic materials. Similarly, the dissipation factor is very low. Dielectric strength ranges from about 500-600 volts per mil for the various compounds these values are quite high. Thus, both... 

Table III. Electrical Properties of Polyphenylene Sulfide Compounds...

We report the first syntheses of the selenium and tellurium analogs of the thermoplastic poly-p-phenylene sulfide (PPS), i.e., PPSe and PPTe, by reaction of p-dihalobenzenes with new alkali chalcogenide reagents under conditions significantly milder than those reported for PPS. The chemical, thermal, structural, and electrical properties of PPSe and PPTe are compared to those of PPS. While PPSe exhibits good thermal stability,... 

Many easily oxidized organic sulfides exist, but, of these, tetrathiafulvalene [2] (TTF) has been more extensively researched than most, because of interest in the electrical properties of its salts. Its oxidation potential makes it a reasonable electron donor [3]. Arenediazonium salts were chosen as the partner reagents since their electron-accepting properties had been well explored [4, 5]. Furthermore, reaction of TTF with diazonium salts had recently been discussed in the Russian literature [6], but this reported only the formation of the radical-cation, TTF+. We were keen... 

There are great differences in the electrical properties and disorder for the sulfides of interest, as typical examples manganous sulfide MnS, silver sulfide Ag2S, iron sulfide FeS, and nickel sulfide NiS are described here. In this sequence, the degeneracy of electrons increases, corresponding to a transition to metallic conductivity. 

Reliability of the electrical properties of silicone-based isotropic adhesives has been the major difficulty to overcome and has essentially prevented commercialization. Another problem associated with silicones is that the addition polymerization reaction of silicones must be carefully controlled to prevent cure inhibition from various common chemical contaminants such as amines and sulfides. Other concerns include low-molecular-weight silicone polymer migration onto wirebond pads and very high GTE. There has been some activity in the development of hybrid resins that contain silicone blocks as comonomer with epoxies such that the epoxy processing can be maintained with the added stress reduction property of the silicones [52]. 

The electric properties of polyphenylene sulfide and the ability to injection mold very small parts with great precision have led to the use of a variety of connectors, coil forms, etc., in the electronics industry. For example, a pin cushion connector coil terminal support used in color television is now being volume produced from PPS in a multiple unit. 

The conductivily of molten bismuth sulfide has not been investigated before although much work has been done on the electrical properties of polycrystalline and single-crystal samples... 

Furthermore, the electrical properties can be adjusted by varying the matrix polymer and the filler distribution. Since the material concept allows for the use of almost any polymer matrix, the required material properties, for instance a high temperature resistance, can be provided by the use of polyphenylene sulfide (PPS) as a matrix polymer. The morphological structure, and thus the measured conductivity over the thickness, depend on the ratio of the melt temperatures and viscosities of both the polymer and metal alloy, whereas the passage conductivity is at a similarly high level of >4x10 S/m. 

There has been considerable interest in recent years in nanoparticles based on the cadmium sulfides and sulfoselenides. These materials, referred to as quantum dots, display unique optical and electrical properties that are quite different from the properties exhibited at pigmentary particle size, and are attributed to their semiconductor behaviour. The most apparent of these properties is their intense fluorescence, the emission wavelength of which may be tuned based on particle size. Quantum dots have potential for applications in medicine, displays, lasers and solar energy conversion. 

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