Strong Te Research Articles

Exploring the Effects of Se Basicity on a Te···Se Interaction Supported by a Rigid Indazolium Backbone.

With an interest in chalcogen bonding, we use a rigid indazolium backbone to install a formally zero-valent Se center next to a divalent Te center, allowing us to investigate the effects of oxidation of the Se center on the observed Te···Se interaction. Through spectroscopic and computational comparison of the Se(0) species with its Se(II) counterpart and their monochalcogen analogues, we experimentally and computationally investigate the effect of modulating Se basicity on the resulting Te···Se interaction. Comparison with well-studied naphthalene and acenaphthene variants indicates that the increased basicity of the Se(0) center allows for a comparably strong Te···Se interaction despite longer peri distances and a larger splay angle. Finally, our study illuminates the potential non-innocence of cationic organic substituents in chalcogen-bonding catalysis of the transfer hydrogenation of quinolines.

Elevating Operation Voltage and Suppressing Phase Transition for Honeycomb‐Layered Cathodes by a Dual‐Honeycomb Structure Strategy

Honeycomb‐layered oxides are a class of cathode materials for sodium‐ion batteries with great potential due to their high voltage and high capacity. However, the structural instability and voltage fading during cycling limit their practical application. Herein, it is revealed that Te substitution into Na3Ni2SbO6 induces a new dual‐honeycomb structure, which can elevate the average discharge voltage of the cathode materials from 3.2 to 3.8 V with improved cycle stability and alleviated voltage decay. Synchrotron operando X‐ray diffraction demonstrates that Te substitution can suppress the O3−P3−O1‐phase transition during charge and discharge processes effectively, benefited from the strong TeO covalent bonds. The resulted Na2.2Ni2Sb0.2Te0.8O6 cathode exhibits a high capacity retention of 70.9% after 1000 cycles at 1C, with an elevated operating voltage of ≈3.8 V. Theoretical calculations reveal that the introduced TeO bonds break the symmetric distribution of charge in Ni/Sb honeycomb structure and elevate the operation voltage by increased valence band width. Proper Te substitution can promote the rate and cycle capability of the cathode by suppressing phase transition and decreasing the bandgap.

Study on effective elastic thickness of lithosphere and its tectonic significance in surrounding area of Ordos Block

Based on EIGEN6C4 gravity field model data and ETOPO1 topographic data, we adopt the correlation analysis method based on Fan wavelet to calculate and analyze the distribution characteristics of effective elastic thickness (Te) and load ratio (F) of lithosphere in surrounding of Ordos block. On this basis, the relationship between the lithosphere Te and geological structure, seismic distribution, terrestrial heat flow and crustal deformation is analyzed. The results show that the lithosphere Te in the surrounding area of the Ordos block is obviously different among the tectonic blocks. The lithosphere Te value is low in the south of Qinling orogenic belt and the east of Fen-Wei graben basin. The maximum lithosphere Te value is distributed in the northwest and northeast margin of Ordos block. The lithosphere Te value is negatively correlated with the load ratio F. Earthquakes mainly occur in areas with low lithosphere Te value. Small lithosphere Te value indicates low strength of lithosphere. In such areas, the ability to resist crustal deformation is weak, and it is easy to generate stress accumulation and breed earthquakes. The area with high terrestrial heat flow value corresponds to low lithosphere Te value, showing a negative correlation. However, this negative correlation does not exist in the northwest margin of Ordos Block and Alashan border area, and the eastern margin of Ordos Lvliangshan area. Haiyuan-Liupanshan area has strong tectonic activity, frequent earthquakes and low lithosphere Te value. The internal strain accumulation of Ordos block is small, and the lithosphere Te value is high. The strain rate of the northern Shanxi fault depression zone is large, but the lithosphere Te value is also large, it is speculated that the terrestrial heat flow is the main factor affecting the lithosphere Te value.

Bonding Heterogeneity Inducing Low Lattice Thermal Conductivity and High Thermoelectric Performance in 2D CdTe2

Two-dimensional (2D) materials have emerged as a broad platform for exploring promising thermoelectric materials. Motivated by the fabrication of diverse artificially designed Te-based 2D materials with high thermoelectric performance, here, we predicted 2D hexagonal CdTe and pentagonal CdTe2 for potential thermoelectric materials, using the particle swarm optimization (PSO) method combined with density functional theory. CdTe and CdTe2 show predicted direct/indirect band gaps of 1.82 and 1.96 eV, respectively. Chemical bonding analysis revealed that all the Te atoms in CdTe are coupled through uniform ionic bonding. CdTe2 exhibits bonding heterogeneity, arising from weak the Cd–Te ionic bonding and strong Te–Te covalent bonding. Based on Boltzmann transport theory, we found that the bonding heterogeneity in CdTe2 favors low lattice conductivity. The calculated lattice thermal conductivity of CdTe2 is 0.33 Wm–1 K–1 at 300 K, which was contributed by the weaker coupling between acoustic and optical phonon modes, low group velocities of the acoustic modes, and high lattice anharmonicity. On the other hand, the occupied π*5p, π5p, and σ5p bondings in Te–Te pairs significantly facilitate the electrical conductivity and enhance the Seebeck coefficient of p-type CdTe2. The low thermal conductivity and high power factor in CdTe2 give rise to a high thermoelectric performance at low temperature. Our findings should encourage the exploration of 2D materials for thermoelectric applications with strong bonding heterogeneity.

Nb2O5–TeO2 and Nb2O5–Li2O–TeO2 glasses: Evaluation of elastic properties

Elastic properties of xNb2O5–(1-x)TeO2 and 0.5xNb2O5–0.5xLi2O–(1-x)TeO2 glass systems were evaluated to understand the structural role of Nb2O5 and Li2O in the tellurite network. A correlation between elastic moduli and estimated compositional parameters has-been established on the basis of the bond compression model, Makishima-Mackenzie's theory and Rocherulle et al. model. Furthermore, the theoretical elastic moduli values are compared with the experimental values. Results revealed that, when Nb2O5 is added, NbO6 structural units and strong Te–O–Nb linkages are formed. The enhancement of elastic moduli is attributed to the increase in average cross-link density, ratio of packing density to mean atomic volume, dissociation energy per unit volume and stretching force constant of Nb–O–Te linkages. The discrepancy between experimental and theoretical results was explained in terms of the structural units which are formed in the tellurite network when TeO2 is substituted by Nb2O5 and Li2O.

Thermal, structural and optical properties of Bi2O3-Na2O-TiO2-ZnO-TeO2 glass system

Tellurite glasses have found wide applications in laser, nonlinear optics and optical communication. This paper describes the role of Bi2O3 on the physical and optical properties of glasses with molar composition of xBi2O3-5Na2O-5TiO2-10ZnO-(80-x)TeO2, where x = 5, 8, 10, 12, and 15 mol.% synthesized using conventional melt quenching technique. The thermal properties of the sample glasses, such as glass transition temperature (Tg), onset crystallization temperature (Tx), and glass stability (S), were estimated from the differential scanning calorimetry measurements. The glass stability was found to decrease as Bi2O3 content increased. The decrement was due to: (i) the decomposition of strong TeO4 units into TeO3+1 polyhedra and TeO3 units; (ii) the replacement of strong Te‒O‒Te bonds by weaker Te‒O‒Bi bonds; and (iii) the formation of weak Bi‒O‒Bi bonds that were shown in Raman and FTIR results contributed to the weakening of the glass stability. The measurements from the UV-Vis spectrophotometer indicated a drop in the optical band gap with increasing Bi2O3 content. A low energy band gap is evidence of glasses with high polarizability which could be due to thehigh polarizability of non-bridging oxygen. This finding, among others in this study, shows that the synthesized bismuth-based tellurite glass is suitable as a potential optical material in the optical and photonic applications.

A comprehensive ARPES study on the type-II Dirac semimetal candidate Ir1−xPtxTe2

The transition metal dichalcogenide Ir1−xPtxTe2 displays both superconductivity and a topological band structure. Using angle-resolved photoemission spectroscopy, we obtain a comprehensive understanding of the three-dimensional electronic structure in the normal state of Ir1−xPtxTe2 for doping levels from x = 0.1 to 0.4, which spans the composition range of a superconducting state to a non-superconducting state. Many features of the electronic structure can be attributed to strong Te–Te interactions between the layers of the layered crystal structure and can be resolved by photon energy dependent measurements. We demonstrate that the type-II Dirac fermions can be successfully tuned via Pt doping, where the Dirac point lies close to the Fermi level for x = 0.1. The band evolution vs doping provides a clearer understanding of the relationship between the superconductivity and electronic structure. In addition, the β band in the superconducting samples locates the system close to a type-II van Hove singularity, where spin triplet paring symmetry has been predicted. Our results provide a comprehensive understanding of the band structure of Ir1−xPtxTe2, and we discuss the possibilities of the existence of topological superconductivity in this system.

Experimental and Theoretical Examination of the Photosensitivity Spectra of Structures with In0.4Ga0.6As Quantum Well-Dots of the Optical Range (900–1050 nm)

Solar cells based on a new type of nanostructure (quantum well-dots) have been studied. These quantum well-dots (QWDs) are In0.4Ga0.6As layers with marked composition and thickness modulations. The energies of the observed optical transitions in QWDs turn out to be close to the energies of transitions involving a light hole and a heavy one in a two-dimensional quantum well of the same nominal thickness and composition. The ground-state peak is characterized by strong TE polarization (>70%), while the shorter-wavelength peak is almost unpolarized (<10%).

Synthesis, crystal structures and antioxidant studies of Pd(II) and Ru(II) complexes of 2-(4-methoxyphenyltelluro) ethanol

Pd(II) (1) and Ru(II) (2) complexes of 2-(4-methoxyphenyltelluro)ethanol (L), were synthesized using Na2 [PdCl4] and [Ru (η6-p-cymene)Cl2]2 as metal ion sources. The new complexes (1 and 2) were characterized by 1H, 13C{1H} NMR, FT-IR, UV–Visible spectroscopy and elemental analyses. Their structures were also confirmed by single crystal X-Ray diffraction. The characterizationdata revealed that the ligand L coordinated to M(II) ion as a monodentate telluroether ligand in both 1 and 2. The structure of cis-[PdCl2(L)2] (1) was square planar about Pd in which two molecules of L coordinated to palladium (II) in cis-fashion. Interestingly, two molecules of 1 were held by strong Te⋯Cl and aromatic π⋯π secondary interactions and oriented in staggered conformation with short Pd-Pd [3.1712 (5) Å] distance forming a dinuclear palladium cluster (cis-[PdCl2(L)2])2 (1)2. The complex [Ru (η6-p-cymene)Cl2(L)] (2) has half-sandwich, pueudo-octahedral structure. There exists several intermolecular hydrogen bonds of type: OH⋯Cl and OH⋯O in 1 and CH⋯Cl, CH⋯O and OH⋯Cl in 2. These interactions results in supramolecular assemblies in the new complexes 1 and 2. In-vitro antioxidant activity of L, 1 and 2 was investigated using DPPH assay. Vitamin-C was used as a standard antioxidant. All three compounds showed to exhibit antioxidant activity. The free radical scavenging activity was quantitatively expressed in terms of their IC50 values which found in the order: Vitamin-C ∼2 > L > 1.

Synthesis of intramolecularly coordinated heteroleptic diorganotellurides and diorganotelluroxides: Isolation of monomeric diorganotelluroxide [{2,6-(Me2NCH2)2C6H3}2TeO] and diorganohydroxytelluronium chloride [{2,6-(Me2NCH2)2C6H3}2Te(OH)]Cl

A series of heteroleptic diorganotellurides (2-NMe2CH2C6H4)(R)Te, where R = C6H5 (5), 2-MeC6H4 (6), 2,6-MeC6H3 (7) and 2,6-iPrC6H3 (8) was synthesised from N,N-dimethylbenzylamine via the ortho-lithiation route. Reactions of 5–8 with SO2Cl2 followed by alkaline hydrolysis afforded diorganotelluroxides (2-NMe2CH2C6H4)(R)TeO, where R = C6H5 (10), 2-MeC6H4 (11), 2,6-MeC6H3 (12) and 2,6-iPrC6H3 (13) respectively. A similar alkaline hydrolysis of homoleptic diorganotellurides, {2,6-(Me2NCH2)2C6H3}2Te (9), afforded a co-crystal of [{2,6-(Me2NCH2)2C6H3}2TeO] (14a) and disordered [{2,6-(Me2NCH2)2C6H3}2Te(OH)]Cl (14b) or a completely ordered diorganohydroxytelluronium chloride [{2,6-(Me2NCH2)2C6H3}2Te(OH)]Cl (14c). Heteroleptic diorganotellurides 7–8 and telluroxides 10–14a-b and diorganohydroxytelluronium chloride 14c were characterised by single crystal X-ray diffraction studies. In the molecular structures, the N-donor substituent made five membered chelating ring with the tellurium atom via Te⋯N secondary bonding interactions. Diorganotelluroxide 10 existed in dimeric form exhibiting both intramolecular Te⋯N and intermolecular Te⋯O secondary interactions. Due to the strong intramolecular Te⋯N secondary bonding interactions from the three N-donor substituents, diorganotelluroxide 14a was stabilised in the monomeric form. This is, in fact, the only second example of a discrete monomeric diorganotelluroxide. Again, because of the presence of intramolecular Te⋯N secondary bonding interactions, the diorganotelluroxides 10–14a-b and diorganohydroxytelluronium chloride 14c exhibited downfield 125Te NMR chemical shift as compared with the earlier reported oligomeric or polymeric diorganotelluroxides.

Ionospheric Electron Heating Associated With Pulsating Auroras: Joint Optical and PFISR Observations

AbstractIn a recent study, Liang et al. (2017, https://doi.org/10.1002/2017JA024127) repeatedly identified strong electron temperature (Te) enhancements when Swarm satellites traversed pulsating auroral patches. In this study, we use joint optical and Poker Flat Incoherent Scatter Radar (PFISR) observations to further investigate the F region plasma signatures related to pulsating auroras. On 19 March 2015 night, which contained multiple intervals of pulsating auroral activities, we identify a statistical trend, albeit not a one‐to‐one correspondence, of strong Te enhancements (~500–1000 K) in the upper F region ionosphere during the passages of pulsating auroras over PFISR. On the other hand, there is no discernible and repeatable density enhancement in the upper F region during pulsating auroral intervals. Collocated optical and NOAA satellite observations suggest that the pulsating auroras are composed of energetic electron precipitation with characteristic energy &gt;10 keV, which is inefficient in electron heating in the upper F region. Based upon PFISR observations and simulations from Liang et al. (2017) model, we propose that thermal conduction from the topside ionosphere, which is heated by precipitating low‐energy electrons, offers the most likely explanation for the observed electron heating in the upper F region associated with pulsating auroras. Such a heating mechanism is similar to that underlying the “stable auroral red arcs” in the subauroral ionosphere. Our proposal conforms to the notion on the coexistence of an enhanced cold plasma population and the energetic electron precipitation, in magnetospheric flux tubes threading the pulsating auroral patch. In addition, we find a trend of enhanced ion upflows during pulsating auroral intervals.

Ultrathin 2D Nonlayered Tellurium Nanosheets: Facile Liquid‐Phase Exfoliation, Characterization, and Photoresponse with High Performance and Enhanced Stability

AbstractNonlayered materials are constructed with chemical covalent bonds in all three dimensions, distinct from layered materials, which contain evident structural differences in the horizontal and vertical directions. As a consequence, liquid‐phase exfoliation (LPE), a widely explored technique to obtain 2D layered nanoarchitectures, has not yet been fully characterized for the realization of 2D nonlayered nanostructures. Herein, by virtue of a typical chain‐like structure of crystalline bulk Te with strong TeTe covalent bonds in intrachains and weak Van der Waals forces in interchains, ultrathin 2D nonlayered Te nanosheets are realized by means of an LPE method. The resultant 2D Te nanosheets possess a broad lateral dimension ranging from 41.5 to 177.5 nm and a thickness ranging from 5.1 to 6.4 nm, and its photoresponse properties are evaluated using photoelectrochemical measurements. The 2D Te nanosheets exhibit excellent photoresponse behaviors from the UV to the visible regime in association with strong time and cycle stability for the on/off switching behaviors. The fabrication approach of 2D Te nanosheets would arouse interest in exfoliating other nonlayered 2D materials, which would expand the family of 2D materials.

Interplay between spin-orbit interaction and stripe-type charge-orbital order of IrTe2

We have studied the electronic structure of the stripe-type charge-orbital ordered phase of IrTe2 by means of angle-resolved photoemission spectroscopy. An electron pocket at the Brillouin zone boundary and hole Fermi surfaces around its center are clearly observed in agreement with the band structure calculation for the stripe-type charge-orbital ordered phase. The present study indicates that the hole and electron Fermi surfaces can survive due to the strong Te 5p spin-orbit coupling even under the charge-orbital order. The participant of the Te 5p orbitals to the conduction band provides an interesting interplay between the charge-orbital order and the spin-orbit interaction in IrTe2.

Superstructures at Te/Au(111) interface evolving upon increasing Te coverage

By in-situ low temperature scanning tunneling microscopy, we systematically investigated the superstructure evolution at Te/Au(111) interface upon increasing Te coverage. Te atoms form one-dimensional 3R30∘ chains at ∼0.10 monolayer (ML) coverage. Two two-dimensional chiral superstructures, (111×111)R4.7∘ and (321×321)R10.9∘, are selectively formed with the Te coverage below and above 1/3 ML, respectively. The two chiral superstructures can be converted to each other reversibly by adding Te atoms or moderately annealing. A honeycomb-like superstructure, decorated with adatoms that are distributed in quasi-one-dimensional chains, is observed by further increasing the Te coverage to 4/9 ML. At the Te/Au(111) interface, an interfacial state at −0.65 eV to −0.55 eV below the Fermi level is also resolved by scanning tunneling spectroscopy. The formation of these Te-induced high-order superstructures is accompanied by relaxation of gold atoms in the surface layer, indicating a strong Te–Au interaction. Our work demonstrates a reliable method to fabricate Te nanostructures on noble metals in a controlled way.

Synthesis and halogenation of bis(8-methoxynaphthyl)ditelluride

Abstract The intramolecularly coordinated 8-methoxytellurium compounds (8-MeOC 10 H 6 ) 2 Te 2 ( 3 ), 8-MeOC 10 H 6 TeCl 3 ( 7a ), 8-MeOC 10 H 6 TeBr 3 ( 7b ) and 5-Br-8-MeOC 10 H 6 TeBr 3 ( 7c ) were prepared and fully characterized by multinuclear NMR spectroscopy, MS spectrometry and X-ray crystallography. The intramolecular Te–O coordination of 7a and the related 6-diphenylphosphinoxy-acenaphtyl-5-tellurium trichloride ( 6a ) as well as the related Te–N coordination of the 8-(dimethylamino)-naphthyltellurium trichloride ( 5a ) were analyzed using a set of real-space bond indicators derived from DFT calculations and the electron density-based theories AIM, ELI-D and NCI. Similar electronic parameters were obtained for the weak Te–N and Te–O interactions in 5a and 7a , which are governed by σ-hole bonding. Additional electrostatic interactions between the terminal O atom and the Te atom in 6a result in a significantly shorter and stronger Te–O contact compared to that in 7a . This, in turn, leads to an elongation of the Te–Cl bond opposite to the Te–O bond.

Origin of the strong optical nonlinearity of tellurium oxide–based compounds: The specific case of BaTe2O6

This paper is a contribution to the understanding of the crystal chemistry origin of the strong nonlinear optical properties of tellurium oxide–based compounds. The particular case of the BaTe2O6 (BaTeIVTeVIO6) phase has been investigated. The structure refinement using single crystal X-ray diffraction confirms that the TeIV atom is located in an unclassical TeO5 environment with one exceptionally short Te–O bond (1.82 Å) and four long ones (2.12 Å). The vibrational analysis points out that in this environment, from the spectrochemical point of view, the short bond is at the origin of a quasi-isolated TeIVO2+ molecular ion whereas the four longer bonds traduce weak interactions. Relationships have been established between the TeIV–O bond lengths and the χ(3) susceptibility. The four long bonds, belonging practically to the xz–plane and involving the TeIV d-orbitals contribution, are at the origin of the high χ(3)xxxx and χ(3)zzzz values (30.0 and 44.3 × 10−13 esu respectively). The short Te–O bond, directed along the y–direction, is responsible for the lower χ(3)yyyy value (3.2 × 10−13 esu). This study is the first obvious confirmation for a real crystal lattice of the high superiority of the nonlinear polarizability of the weak intermolecular Te–O bonds over that of the strong molecular Te–O ones.

Electrophilic substitution of acetyltrimethylsilane with tellurium(IV) halides: A synthetic route to 3-methyl-5-(trimethylsilyl)-1,2-oxatellurol-1-ium halides

The reaction of tellurium tetrahalides, TeX4 (XCl. Br) with acetyltrimethylsilane in CCl4 at ambient temperature, unlike that of the aryltellurium trichlorides, ArTeCl3 that give the expected electrophilic substitution products, Ar(Me3SiCOCH2)TeCl2, (Ar = 1-C10H7, 2; 2,4,6-Me3C6H2, 3), afforded novel silylated heterocycles, 3-methyl-5-(trimethylsilyl)-1,2-oxatellurol-1-ium halides 1a and 1b. These Te(II) heterocyclic compounds undergo halide exchange with sodium iodide and also add dihalogens oxidatively to afford the corresponding iodide, 1c and the Te(IV) trihalides, 5a and 5b respectively. A large lowering of ν(CO) is indicative of strong Te⋯OC interactions among these heterocycles, and is also substantiated by single-crystal X-ray diffraction data for 3-methyl-5-(trimethylsilyl)-1,2-oxatellurol-1-ium chloride. The 125Te chemical shifts for the new 10-Te-3 telluranes and 12-Te-5 pertelluranes that involve tellurium bound to two highly electronegative atoms (O, X) are among the highest (downfield) reported for organotellurium(II) and (IV) compounds.

Semiconducting Polymers Containing Tellurium: Perspectives Toward Obtaining High-Performance Materials

The development of high-carbon-content polymers for optoelectronics is an area of intense research; however, carbon-rich materials have certain limitations that arise from their composition. Some of these limitations can be overcome by the judicious incorporation of heavier elements which do not significantly change the carbon content to a point where it adversely affects cost and processability. Here we examine the use of tellurium as a heavy atom in the design of optoelectronic polymers. Group 16 atom (O, S, Se, Te) substitution is a promising strategy for the development of high performance materials for organic electronic applications. The use of tellurium in place of selenium or sulfur in conjugated polymers lends new properties to these materials such as red-shifted optical absorption, high polarizability, high dielectric constant, and strong intermolecular interactions. These properties are favorable for organic photovoltaics (OPVs) and organic field effect transistors (OFETs). In particular, extending the absorption range to the near-IR allows for more efficient solar harvesting since low-energy photons are most abundant. Additionally, strong Te–Te interactions lead to enhanced interchain electronic coupling, which is expected to facilitate charge transport. The use of polymers containing tellurophene, the tellurium analogue of the well-studied thiophene, has only recently begun to emerge in the literature. New synthetic routes have been developed, and there now exist a handful of tellurophene-containing polymers that have been synthesized and used to fabricate OPVs and OFETs. Their performance in OPVs has not surpassed that of their lighter chalcogen analogues; however, the use of tellurophene-containing materials is a young field, and continued efforts in the development of new materials and device optimization should lead to improved performance. In this Perspective we discuss the current status of tellurium-containing polymers in terms of their synthesis, properties, and performance. We highlight the challenges that have been overcome thus far and emphasize those that should be the focus of future work. This includes overcoming synthetic challenges and developing an understanding of the current limitations in device performance with tellurium-containing polymers through studies of materials properties and excited state dynamics. We also suggest new applications and directions for tellurium-containing materials beyond OPVs and OFETs.

Investigations of thermal, structural and optical properties of tellurite glass with WO3 adding

Tellurite glasses with the molar composition (89-x) TeO2–10TiO2–1Nd2O3–xWO3 (x=0, 10 and 20mol%) were prepared by the conventional melt-quenching technique. The effects of WO3 concentration on the structural, thermal and optical properties of tellurite glasses have been discussed. From the differential scanning calorimetry measurements, thermal properties such as glass transition temperature Tg, crystallization temperature Tx, and thermal stability ΔT are estimated. It was found that ΔT increases with the increase of WO3 composition which can indicate a reinforcement of the glassy network. Both Raman and FTIR results show that the addition of WO3 induced a depolymerisation of tellurite glass since the Te–O–Te inter-chain linkages are progressively substituted by stronger Te–O–W bridges that are at the origin of the increase of the thermal stability of the glass.The optical band gap energy values corresponding to the direct and indirect allowed transitions and the Urbach energy values of the prepared tellurite glasses have been calculated from optical absorption edges. The results show an important decrease of the optical band gap with the increase of WO3 concentration. It was assigned to W6+ ions that could have a role as network modifier. The Urbach energy was found to decrease with WO3 compositions which suggest the possibility of long range order. The refractive index and extinction coefficient were obtained by spectroscopic ellipsometry. Higher values for the refractive index are recorded due to the high polarizability of non-bridging oxygen. It is observed also that the refractive index, n increases with increasing WO3 content. It is established that there is a trend by which the energy gap decreases with increasing refractive index and increasing the polarizability of the oxide ions. The complex dielectric function ε, relative to each sample, was estimated from regression analysis. The material studied here has potential application as optical fiber.

Te 5porbitals bring three-dimensional electronic structure to two-dimensional Ir0.95Pt0.05Te2

We have studied the nature of the three-dimensional multiband electronic structure in the two-dimensional triangular lattice Ir${}_{1\ensuremath{-}x}$Pt${}_{x}$Te${}_{2}$ ($x=0.05$) superconductor using angle-resolved photoemission spectroscopy (ARPES), x-ray photoemission spectroscopy (XPS), and a band structure calculation. ARPES results clearly show a cylindrical (almost two-dimensional) Fermi surface around the zone center. Near the zone boundary, the cylindrical Fermi surface is truncated into several pieces in a complicated manner with strong three dimensionality. The XPS result and the band structure calculation indicate that the strong Te 5$p$-Te 5$p$ hybridization between the IrTe${}_{2}$ triangular lattice layers is responsible for the three dimensionality of the Fermi surfaces and the intervening of the Fermi surfaces observed by ARPES.