Search results for "Niobium"

Electrochemical growth and physico-chemical characterization in organic medium of Nb2O5 thin films

2008

Investigations about the energetics and the electrical properties of niobium thin film, electrochemically grown, were performed in an organic solution of acetonitrile and lithium perchlorate. The study of the energetics of the Nb O /organic solution interface was performed by means of a non-destructive optical technique, photocurrent 2 5 spectroscopy. By means of this technique, it was possible estimating the value of the flat band potential and locating conduction and valence band. A more cathodic value of flat band potential in respect with acidic solution was found in organic medium. From impedance spectra, the electrical circuit that gives best fitting values is constituted by two resis…

ChemInform Abstract: Nb2Te3, a Niobium Sesquitelluride with Te22- Groups.

2010

The new binary compound Nb2Te3 was synthesized by reduction of NbTe2 with Ga metal; different from the formally analogous Ta2Te3 it crystallizes in the Mo2As3 structure type; based on the results of band structure calculations Nb2Te3 is metallic with quasi one-dimensional metal electronic properties.

Bis(η-tert-butylcyclopentadienyl)hydridoniobium Ditelluride, a Convenient Reagent for the Synthesis of Polynuclear Metal Telluride Complexes

2002

Niobium implantation effects in BaTiO3 and SrTiO3

1992

Abstract Single crystals of BaTiO3 and SrTiO3 have been implanted at room temperature with 150 keV Nb+ ions to doses ranging from 1014 to 1017 ions cm2. The structure and the oxidation state of the damaged layer have been investigated by Rutherford backscattering-ion channeling and electron spectroscopy, respectively. SrTiO3 is rendered amorphous at relatively low doses of 2 × 1015 ions cm−2, but the damage is efficiently annealed at 450°C for 1 2 h. For both materials, the oxidation state of niobium varies from + 5 to + 2 along the depth. Moreover, a considerable chemical shift (2.3 eV) is observed for barium in BaTiO3.

[{(C5Me5)2Nb}2PdTe4], a heterometallic palladium telluride cluster with a planar PdTe4 fragment

2007

Abstract The reaction of [ Cp 2 ∗ Nb ( Te 2 H ) ] (Cp∗ = η5-C5Me5) with [Pd(DBA)2] (DBA = dibenzylidenacetone) and dppm (bis(diphenylphosphanyl)methane) gave the new tetratelluropalladate cluster [ ( Cp 2 ∗ Nb ) 2 PdTe 4 ] (1), which has been characterised by means of elemental analysis, FD-MS and X-ray crystallography. The structure of compound 1 contains a planar PdTe4 rectangle to which two niobocene groups are coordinated. DFT calculations on the hypothetical [PdTe4]2− anion and comparison of the results with those of the W and Ni homologues show that the planar arrangement of Te ligands in 1 is due to the intrinsic property of the central Pd atom.

Electrochemical and chemical reduction of niobocene dichlorides in the presence of carbon dioxide

1995

Abstract The chemical and electrochemical reduction of the niobocene dichlorides [Nb(η5-C5H4SiMe3)2Cl2]1, [Nb(η5-C5Me5)2Cl2] 2 and [Nb(η5-C5Me4Et)2Cl2] 3, in the presence of carbon dioxide has been investigated. Formation of compounds of the type [Cp2Nb(CO2)] and [Cp2(∗)NbCl(CO2))] 1 has been established by means of IR, ESR and/or NMR spectroscopy. They contain a labile η2-CO2. The order of stability increases with the degree of substitution the Cp. Less stable intermediates in the reduction of the system [Cp2NbCl2]/CO2 are discussed on the basis of cyclovoltammetric and coulometric data.

<title>Dielectric polarization in <emph type="1">x</emph>PbZn<formula><inf><roman>1/3</roman></inf>&l…

2005

Manifestation of relaxor properties in the x PbZn1/3Nb2/3O3-(1-x )PbSc1/2Nb1/203 ceramic solid solution system, similar to those observed in lead magnesium niobates, are reported. Dependence of the effective dielectric permittivity and dielectric loss on the temperature at frequencies of 0.1-10 Hz and different measuring field amplitudes E 0 are examined ceramic samples of 0.05PbZn1/3Nb2/3O3-0.95PbSc1/2Nb1/203. It is demonstrated that the temperature at which the dielectric permittivity has a maximum, T m, decreases with the increase of E 0. The dependence of T m on the frequency in both strong and weak fields is shown to follow the Vogel-Fulcher law, with Voger-Fulcher temperature decreasi…

<title>Dielectric response to low and infra-low frequency in layered ferroelectrics</title>

2006

Features of dielectric response to frequencies in the 0.25.1000 Hz range in ceramic samples of BaBi2Nb2O9, Na0,5Bi8.5Ti2Nb4O27, Na0,5Bi8.5Ti2Ta4O27, and K0,5Bi8.5Ti2Nb4O27 compounds are reported. Considerable relaxation of e'(T) and e"(T) maximums has been observed at all frequencies in BaBi2Nb2O9. Na0,5Bi8.5Ti2Nb4O27 and Na0,5Bi8.5Ti2Ta4O27 are characterised by broad maximums on e'(T) at frequencies below 100 Hz and a weak anomaly in K0,5Bi8.5Ti2Nb4O27 at temperatures well below the paraelectric phase transition. Increasing values of e' are observed at low temperatures in compounds containing sodium. The observed features of dielectric response are explained by largescale charge fluctuatio…

Growth and Characterization of Anodic Films on Al-Nb Alloys

2006

Abstract The anodizing behaviours of sputtering-deposited aluminium, niobium and Al-Nb alloys, containing 0.4, 7.5, 21, 40 and 55 at.% niobium, have been examined in 0.1 M ammonium pentaborate electrolyte with interest in the morphology, structure and electronic properties of the anodic oxides. Transmission electron microscopy revealed amorphous oxides, containing units of Nb2O5 and Al2O3, with formation ratios intermediate between those of anodic alumina and anodic niobia. Photocurrent spectroscopy provided increased understanding of the electronic properties of the anodic films, suggesting the formation of “mixed oxides” with insulating behaviours. The estimated band gap values are correl…

Physicochemical characterisation of thermally aged anodic films on magnetron sputtered niobium

2010

The influence of thermal aging, at intermediate temperature (1h at 250°C) and in different environments, on the electronic and solid-state properties of stabilized 160 nm thick amorphous anodic niobia, grown on magnetron sputtered niobium metal, has been studied. A detailed physicochemical characterisation of the a-Nb2O5/0.5M H2SO4 electrolyte junction has been carried out by means of photocurrent and electrochemical impedance spectroscopy as well by differential admittance measurements. A change in the optical band gap (3.45 eV) of niobia film has been observed after aging (3.30 eV) at 250°C in air for 1 hour. A cathodic shift (0.15-0.2 Volt) in the flat band potential of the junction has …