Tellurium Oxide Research Articles

Dielectric studies on tellurium oxide thin films

Tellurium has been evaporated in an r.f. glow discharge of oxygen onto negatively-biased glass substrates at room temperature. These tellurium oxide thin films have been used as dielectrics in capacitors. The variations of capacitance, C, and dielectric loss, e″, with frequency in the range of 0.5 to 30 kHz at various temperatures (300 to 443 K) have been studied. The temperature coefficient of capacitance and the dielectric constant for the material have been evaluated. The e′' spectrum reveals a loss peak and a loss minimum, both shifting towards higher frequences with increasing temperatures. The maximum in the dissipation factor is explained on the basis of a dipolar relaxation phenomenon. The activation energy for the process has also been evaluated.

Palladium-catalyzed allylic oxidation of olefins by t-butyl hydroperoxide and tellurium(IV) oxide

Treatment of several cyclic olefins, β-pinene, allylbenzene, and estragole with palladium(II) salt in acetic acid in the presence of t-butyl hydroperoxide and tellurium(IV) oxide afforded mainly the corresponding allylic acetates. The reaction proceeded catalytically with palladium(II) salt, t-BuOOH working as a reoxidizing agent.

Preparation and characterization of mixed oxides of selenium and tellurium

Double oxides of Se and Te of composition Te3SeO8, Te2Se2O9, and TeSeO4 have been obtained for the first time by solid-state reactions between the corresponding elements and their oxides. The preparative conditions and the characterization of these compounds by thermal analysis, X-ray diffraction, and i.r. spectroscopy are discussed.

ChemInform Abstract: ORGANOTELLURIUM CHEMISTRY. THE TELLUROXIDE ELIMINATION REACTION

AbstractDie Telluride (I) werden durch Bromierung mit N‐Bromsuccinimid (NBS) und anschlie‐ βende alkalische Behandlung in die Oxide (II) übergeführt, die bei 80°C zu einem 1:1‐Gemisch aus (III) und (I) gespalten werden.

Selective 1,4-diacetoxylation of conjugated dienes with tellurium (IV) oxide

Oxidation of several linear conjugated dienes with tellurium (IV) oxide and lithium bromide in acetic acid affords an isomeric mixture of the corresponding diacetoxyalkenes (1,2- and 1,4-addition products), 1,4-isomer being highly selectively produced when the ratio of LiBr/TeO 2, is 5–10.

Organotellurium chemistry. The telluroxide elimination reaction

In an effort to clarify the nature of the organotelluroxide elimination reaction, dodecyl-(4-methoxy-phenyl)tellurium oxide and dioxide were thermolysed; mechanisms involvnig tellurenic acid for the oxide and a 1,2-oxygen shift for the dioxide are proposed.

Pyridines by propylene ammoxidation: Catalyst structure and reaction selectivity

Catalysts prepared by precipitating silica-alumina on preformed tellurium oxide or tellurium/antimony mixed oxides were selective for the direct ammoxidation of propylene to pyridines, and catalysts prepared in the reverse order acted only as poor oxidation catalysts. A study by polarizing optical microscopy and by scanning electron microscopy/electron probe microanalysis indicated that the selective catalysts consisted of small particles of the tellurium oxide-based phase in a silica-based acidic matrix and the unselective catalysts consisted of the tellerium-antimony phase uniformly distributed around, and probably within, the pores of the particle. The mechanism of the selective ammoxidation of propylene with oxygen and ammonia may involve the retention of ammonia and diffusion of propylene and oxygen in the silica-alumina phase, oxidation of propylene at the tellerium oxide-based catalyst to a carbonyl compound, and conversion to pyridines of the carbonyl compound during counterdiffusion through the ammonia-loaded acidic phase.

Oxidation properties of II–VI compound surfaces studied by low-energy electron-loss spectroscopy and 21 eV photoemission spectroscopy

Oxidation properties of ZnSe, ZnTe, CdSe, and CdTe surfaces were studied. The following combinations of experimental techniques were used: electron-energy-loss spectroscopy on vacuum-cleaved ZnSe(110) surfaces and on Ar+ bombarded-annealed surfaces of ZnSe, ZnTe, CdSe, and CdTe. Photoemission spectroscopy also was used on a vacuum cleaved ZnTe(110) surface. The oxygen uptake is very slow with exposures to molecular oxygen. Thus oxide overlayers were prepared by an electron-beam irradiation technique which greatly enhanced the oxygen uptakes. Changes in loss spectrum detected on oxidation of CdTe can be explained by formation of TeO2. For the case of ZnTe, the shifted Te 4d loss due to TeO2 appears at the oxygen coverage, ϑ, of about 0.5 of a monolayer, and losses characterizing formation of ZnO are seen at ϑ≳1. The oxide overlayer on ZnTe is composed of TeO2 and ZnO and, in addition, an unidentified complex oxide for the heavily oxidized surface. On further oxygen exposures and beam irridation of this oxide, tellurium oxides sublime away from the surface, leaving an oxide layer rich in ZnO. In the case of the Se compounds, the oxygen adsorbs on the surface Se atoms without breaking the back bonds at the initial stages of oxidation (ϑ≳0.5). For ϑ≳0.5, back bonds are broken, resulting in the formation of the bulklike cation oxide and, perhaps, the anion oxide, SeO2. Because of its high vapor pressure, the SeO2 may sublime away from the surface, leaving the overlayer rich in ZnO for ZnSe and rich in CdO for CdSe. Thus, for very heavy oxidation, the following oxides were found; TeO2 on CdTe, CdO on CdSe, and ZnO on ZnTe and ZnSe. For each II–VI the single oxide listed above was that with the largest heat of formations.

Mössbauer and T.G.A studies of some hexahalotellurate(IV) salts

The reaction of tellurium(IV) oxide with concentrated hydrochloric acid gives a solution from which (Ph 4As) 2TeCl 6 may be precipitated. This material has 125Te Mössbauer parameters which suggest that the anion may be distorted towards, C 3v symmetry. By contrast the hexabromotellurate and the hexachlorotellurate formed when a benzene solution of TeCl 4 is treated with Ph 4AsCl are ‘normal’. TGA studies show that the ammonium and tetramethyl ammonium hexachloro- and hexabromotellurates decompose more or less cleanly to tellurium tetrahalide ad ammonium halide. The decomposition of the tetraphynlarsonium salts is more complex.

Study of Acentricity in Complex Perovskites Based on Tellurium Oxide Using Optical Second Harmonic Generation (SHG)

Study of Acentricity in Complex Perovskites Based on Tellurium Oxide Using Optical Second Harmonic Generation (SHG)

Liquid phase diacetoxylation of 1,3-butadiene with PdTeC catalyst

The catalytic properties of PdTe bimetallic system supported on charcoal (PdTeC) for liquid-phase diacetoxylation of butadiene was studied in comparison with other heterogeneous (PdC, PdAsC, PdBiC, PdSbC, PdSeC, Pd-TeAl 2O 3, or PdTeSiO 2) or homogeneous [Pd(OAc) 2Cu(OAc) 2KOAc or PdCl 2CuCl 2KOAc] palladium-based catalysts. The highest activity for 1,4-diacetoxylation was obtained with the PdTeC catalyst prepared from Pd(NO 3) 3 and TeO 2 dissolved in aqueous nitric acid solution, for all the catalysts studied. The reaction seems to proceed catalytically on the surface of this supported bimetallic system, and its active species is suggested to be some palladium tellurides, in which Pd serves by a redox mechanism, being coupled with Te. The PdTeC system catalyzed the direct diacetoxylation of butadiene, which is considered to proceed via π-allyl-type intermediate. The use of the ratio of Pd:Te ∼- 10:1 on charcoal is the most effective; a higher content in Te results in a lowering of the activity, possibly brought on by the unfavorable deposition of tellurium oxides on the catalyst surface. With the PdTeC system, the following values of selectivities of diacetoxybutenes were obtained: trans-1,4-diacetoxy-2-butene, 75%; cis-1,4-diacetoxy-2-butene, 14%; and 3,4-diacetoxy-1-butene, 10%.

Oxidation of propylene over tellurium oxides and Cd−Te−Mo−O and Mn−Te−Mo−O systems

The catalytic behavior of the Cd−Te−Mo−O and Mn−Te−Mo−O systems in the selective oxidation of propylene to acrolein has been related to the MTeMoO6 phases in the region rich in Te and to the MMoO4 phases with Te as dopant in the region poor in Te. In view of the possible relevance of Te4+ and Te6+ ions to catalysis, the behavior of the different forms of tellurium oxide is also discussed.

Oxidation in air and thermal desorption on PbTe, SnTe and Pb 0.8Sn 0.2Te Surfaces

XPS and LEED measurements of the oxidation in air and thermal desorption on PbTe, SnTe and Pb 0.8Sn 0.2Te surfaces are presented. The initial cleaning of the surface for the oxidation experiments by Ar sputtering (3 kV) yields immediately a perfect, unreconstructed Pb 1− x -Sn x Te surface. The oxidation process is determined by the preferential oxidation of Sri. The surface is strongly depleted of tellurium and enriched with lead and especially tin. During thermal desorption tellurium oxide is lost first from the surface. Lead and tin oxide are too stable to become thermally desorbed during our heat treatment (350°C, 30 min). The oxidation and thermal desorption can be understood as a competing chemical reaction between the stable SnO 2 and the unstable TeO 2.

Correlation between Surface Properties and Detection Characteristics of Cadmium Telluride Detectors

Up to now, only very little attention has been given to the surface properties of cadmium telluride detectors, the best reported results being given When lapped surfaces, a result which is rather strange, when compared to the general behaviour of semiconductors. In order to better understand the mechanism involved at a metal-cadmium telluride contact, the properties of mechanically polished, chemically etched and also oxidized surfaces of cadmium telluride crystals have been investigated using various methods including ellipsometry, Rutherford backscattering in channelling conditions and secondary ion mass spectroscopy. Most important contaminants have been identified for each kind of preparation. Furthermore, it could be shown that if polished and certain oxidized surfaces are quite stable in air, etched surface become covered by a tellurium oxide layer, whose thickness increases even after very long periods of time. Detectors have been prepared afterwards on identical samples having received the various surface treatments and the main detectors properties investigated, especially noise, resolution, efficiency and polarization.

Low-energy-electron loss spectroscopy of ZnTe (110) and (111) surfaces. II. Oxidation properties

The oxidation properties of ZnTe (110) and (111) surfaces have been studied by low-energy-electron loss spectroscopy and Auger-electron spectroscopy. Oxygen adsorption of about half-monolayer coverage was observed at an exposure of ${10}^{13}$ L of molecular oxygen, for both ordered (110) and (111) surfaces. Electronbeam irradiation drastically stimulated oxidation and oxygen adsorption larger than one-monolayer coverage occurred. Loss spectra of the oxygen-contamined surfaces exhibit an oxygen-derived surface state lying \ensuremath{\sim} 0.3 eV above the valence-band maximum, probably within the band-gap region, for the surface with adsorbed oxygen, and a Zn-$3d$ core-level loss due to ZnO and a Te-$4d$ core-level loss due to Te${\mathrm{O}}_{2}$ for the heavily oxidized surface. This finding implies that both zinc and tellurium oxides are involved in the oxidation of ZnTe. The chemical compositions of the clean and oxidized surfaces are discussed by using a layer model.

Novel tellurium oxide fluorides: cis- and trans-F4Te(OTeF5)2, cis- and trans-F2Te(OTeF5)4, FTe(OTeF5)5, and Te(OTeF5)6

Novel tellurium oxide fluorides: cis- and trans-F4Te(OTeF5)2, cis- and trans-F2Te(OTeF5)4, FTe(OTeF5)5, and Te(OTeF5)6

ChemInform Abstract: THE CHEMICAL TRANSPORT OF TELLURIUM(IV) OXIDE AND TELLURIUM OXIDE CHLORIDE (TE6O11CL2) WITH TELLURIUM(IV) CHLORIDE, CHLORINE, AND HYDROGEN CHLORIDE

Chemischer InformationsdienstVolume 9, Issue 18 Preparative Inorganic Chemistry ChemInform Abstract: THE CHEMICAL TRANSPORT OF TELLURIUM(IV) OXIDE AND TELLURIUM OXIDE CHLORIDE (TE6O11CL2) WITH TELLURIUM(IV) CHLORIDE, CHLORINE, AND HYDROGEN CHLORIDE H. OPPERMANN, H. OPPERMANNSearch for more papers by this authorE. WOLF, E. WOLFSearch for more papers by this author H. OPPERMANN, H. OPPERMANNSearch for more papers by this authorE. WOLF, E. WOLFSearch for more papers by this author First published: May 2, 1978 https://doi.org/10.1002/chin.197818027AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume9, Issue18May 2, 1978 RelatedInformation

Almost perfect epitaxial multilayers

XPS and LEED measurements of the oxidation in air and thermal desorption on PbTe, SnTe and Pb0.8Sn0.2Te surfaces are presented. The initial cleaning of the surface for the oxidation experiments by Ar sputtering (3 kV) yields immediately a perfect, unreconstructed Pb1−x-SnxTe surface. The oxidation process is determined by the preferential oxidation of Sri. The surface is strongly depleted of tellurium and enriched with lead and especially tin. During thermal desorption tellurium oxide is lost first from the surface. Lead and tin oxide are too stable to become thermally desorbed during our heat treatment (350°C, 30 min). The oxidation and thermal desorption can be understood as a competing chemical reaction between the stable SnO2 and the unstable TeO2.

Compact vapour deposition system

XPS and LEED measurements of the oxidation in air and thermal desorption on PbTe, SnTe and Pb0.8Sn0.2Te surfaces are presented. The initial cleaning of the surface for the oxidation experiments by Ar sputtering (3 kV) yields immediately a perfect, unreconstructed Pb1−x-SnxTe surface. The oxidation process is determined by the preferential oxidation of Sri. The surface is strongly depleted of tellurium and enriched with lead and especially tin. During thermal desorption tellurium oxide is lost first from the surface. Lead and tin oxide are too stable to become thermally desorbed during our heat treatment (350°C, 30 min). The oxidation and thermal desorption can be understood as a competing chemical reaction between the stable SnO2 and the unstable TeO2.

Epilayer-substrate interfaces of Sn-doped GaAs

XPS and LEED measurements of the oxidation in air and thermal desorption on PbTe, SnTe and Pb0.8Sn0.2Te surfaces are presented. The initial cleaning of the surface for the oxidation experiments by Ar sputtering (3 kV) yields immediately a perfect, unreconstructed Pb1−x-SnxTe surface. The oxidation process is determined by the preferential oxidation of Sri. The surface is strongly depleted of tellurium and enriched with lead and especially tin. During thermal desorption tellurium oxide is lost first from the surface. Lead and tin oxide are too stable to become thermally desorbed during our heat treatment (350°C, 30 min). The oxidation and thermal desorption can be understood as a competing chemical reaction between the stable SnO2 and the unstable TeO2.