Partial Substitution Of Copper Research Articles

Partial Substitution of Copper with Nickel for the Superconducting Bismuth Compound and Its Effect on the Physical and Electrical Properties

Partial Substitution of Copper with Nickel for the Superconducting Bismuth Compound and Its Effect on the Physical and Electrical Properties

High-conducting Bi4V1.8Cu0.2-xSbxO10.7+3x/2 ceramics: Structural, microstructural, electrical and optical properties

The partial substitution of copper by antimony in Bi4V1.8Cu0.2O10.7 compounds leds to the solid solution Bi4V1.8Cu0.2-xSbxO10.7+3x/2 (0.00 ≤ x ≤ 0.20). X-ray diffraction and thermal analysis showed that for all compositions, the obtained phases are isotype to the tetragonal γ or γ′ form of Bi4V2O11. The effect of Sb5+ doping on electrical conductivity was studied using electrochemical impedance spectroscopy in the temperature range 200–700 °C. The changes in slope observed in the Arrhenius plots correspond to the structural transitions that occur within the material. The band gap was determined by DRS spectra, BiCuSbVOx materials have a very low gap band (1.77–1.80 eV) compared to parent phase Bi4V2O11 and the most of BIMEVOX semiconductor materials. The band located around 860 cm−1 in Raman spectroscopy is attributed to V–O bond and more especially to V–O2 bond.

Cobalt substitution effects on critical current, inter-grain full penetration field, and critical temperature study for Tl2Ba2Ca2Cu3-xCoxOy bulk superconductor, where x is from 0.005 to 0.050

Thallium-based cuprates are known to exhibit high critical temperatures and currents. Usually, partial substitution of copper by transition elements leads to the suppression of superconducting properties. This contribution reports on the studies of Tl2Ba2Ca2Cu3-xCoxOy. All specimens were found to be superconductors with critical temperatures of 102.4 K, 112.9 K, 112.2 K, 113.5 K, 112.8 K, and 94.8 K for x = 0.005, 0.010, 0.020, 0.030, 0.040, and 0.050, respectively. The samples were characterised by scanning electron microscopy, X-ray diffraction, AC susceptibility, resistance, and vibrating sample magnetometry.

Poly (3, 4-ethylene dioxythiophene) Supported Palladium Catalyst prepared by Galvanic Replacement Reaction for Methanol Tolerant Oxygen Reduction

Herein, we propose a facile electrochemical approach for the synthesis of Pd loaded poly 3, 4-ethylenedioxythiophene (PEDOT) electrodeposited on glassy carbon electrode (GCE) resulting in high surface area. The catalyst preparation is initiated with EDOT polymerization on GCE surface by electrochemical potential cycling method, followed by the electrodeposition of Cu from a 2 mM solution of CuSO4 in 0.1 M NaClO4 at a constant potential of +0.34 V vs. SHE in the form of Cu nanocubes on the PEDOT surface. Pd-PEDOT catalyst was then prepared by the partial substitution of copper by galvanic displacement with various concentrations of PdCl2. The prepared Pd/PEDOT electrocatalyst is found to be methanol resistant indicating its usefulness as fuel cell cathode. The prepared catalyst supports two electron transfer of oxygen reduction reaction in 0.5 M H2SO4. The effects of Pd and Cu contents and the quantity of PEDOT, mass and specific activities were studied. At a relatively low Pd loading of 0.57 ng/cm2, the Pd/PEDOT should be a cost-effective alternative cathode catalyst for direct methanol fuel cells, DMFCs. This work explains the usefulness of PEDOT as good catalyst supporting material which is prepared by an eco-friendly electrochemical route.

Improvement the Superconducting properties of TlBa2 Ca2 Cu3xNix O 9-δ superconducting compound by partial substitution of copper with nickel oxide on the

In this study is presented the partial replacement of copper with nickel TlBa2Ca2 Cu3xNix O9-δ superconductor with (x=0,0.2,0.4,0.6,0.8,1.0). The samples were prepared in a solid state reaction method with a 850 Co sintering temperature for 24 hours. Structural of the samples were studied by using X-ray powder. The XRD analysis showed that a tetragonal diagram and polycrystalline structures with a majority phase 1223 and changes in nickel concentrations resulted in a change in the parameters of lattice parameters a, b, c axis c / a, mass density and Volume fraction. Four prop technique were used to test the electrical resistivity to determine the critical temperature at zero resistance Tc(offset). The best transfer temperature was obtained from the TlBa2Ca2Cu2.4Ni0.6O9-δ sample, which is equal to 134.6 Kelvin.

Synthesis, thermal and electrical properties of Al-doped Bi4V1.8Cu0.2O10.7

Partial substitution of copper with aluminum in Bi4V1.8Cu0.2O10.7 has led to the Bi4V1.8Cu0.2−xAlxO10.7+x/2 solid solution. X-ray diffraction and thermal analysis have shown that the compounds with x=0.05 and x=0.10 are tetragonal with γ′ form of Bi4V2O11, while the compound with x=0.15 is of β polymorph. The effect of Al3+ doping on electrical conductivity has been studied using Electrochemical Impedance Spectroscopy. The electrical conductivity of doped samples along with the amount of Al3+ has been studied by electrochemical impedance spectroscopy in the temperature range 250–700°C. The slope changes observed in the Arrhenius plots agree with the microstructural transitions occurring in these compounds. The highest ionic conductivity values are obtained for the sample with x=0.05.

Molecular dynamics study of Pb-substituted Cu(1 0 0) surface layers

Using molecular dynamics (MD) and phenomenological n-body potentials from the literature, we have studied the structure of the uppermost layers of low-index surfaces in copper after partial substitution of copper by lead atoms at randomly selected sites. We found that lead atoms substituting copper strongly perturb the positions of nearest and of next-nearest neighbors thus triggering the setup of a disordered, nanometer-thick amorphous-like surface layer. Equilibrium atomic density profiles, computed along the [1 0 0] crystallographic direction, show that amorphous overlayers are largely metastable whereas the system displays a structured compositional profile of lead segregating at the interfaces. Similarities between our results and experimental findings are briefly discussed.

Ionic conductivity and chemical diffusion in superionic LixCu2−xS (0 ≤ x ≤ 0.25)

AbstractThe ionic conductivity and the conjugate chemical diffusion of cations and electron holes in LixCu2−xS (0 ≤ x ≤ 0.25) compositions are studied in the temperature range 623–467 K. In accordance with prediction of the known “mixed mobile ions effect” the partial substitution of copper by lithium in copper sulfide leads to decreasing of the ionic conductivity and it is linked to an increase of activation energy of the ionic conductivity. In comparison with pure copper sulfide the chemical diffusion coefficients in the lithium‐contained compounds are smaller too. The observed values of the activation energy of the chemical diffusion are close to those of the activation energy of the ionic conductivity. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

LOCAL ELECTRONIC STRUCTURE OF DOPING ATOMS IN MA2Can-1CunO2n+3 HIGH-Tc SUPERCONDUCTORS WITH [M-12(n-1)n] TYPE STRUCTURES

Results of X-ray fluorescence measurements of MA 2 Ca n-1 Cu n O 2n + 3 compounds with [ M -12(n-1)n] type structures, ( C 0.8 N 0.2 Sr 2 CuO 5.3, [ Cu 0.25 (C,N) 0.75] Sr 2 CaCu 2 O y, Cu 0.5 V 0.5 Sr 2 CaCu 2 O 7.5, Cu 0.5 V 0.5 Sr 2 Ca 2 Cu 3 O 9.4, Cu 0.5 V 0.5 Sr 2( Ca 3.6 Sr 0.4) Cu 5 O 13.5 and Cu 0.5 V 0.5 Sr 2( Ca 4.7 Sr 0.3) Cu 6 O 15.3, are presented. The experiments show that C-atoms form a distorted CO 3 oxyacid group with a partial substitution of copper and nitrogen atoms in the M-sites. We conclude that the CO 32- group in (C,N) Sr 2 Ca n-1 Cu n O y and (Cu,C,N) Sr 2 Ca n-1 Cu n O y is substituted by the NO 2- which induces the creation of the hole carriers in these compounds. We have found that V-atoms in the given compounds form ( VO 4)3- tetrahedrons and have a pentavalent state.

Local and electronic structure of carbon and nitrogen atoms in oxycarbonitrate superconductors

Results of X-ray fluorescence measurements of new oxycarbonitrate superconductors MSr 2Ca n−1 Cu n O y ( n=1 or 2 and M=Cu, C or N) are presented. The experiments show that C atoms form a distorted CO 3 oxyacid group with a partial substitution of copper and nitrogen atoms in the M sites. Based on the comparison of nitrogen Kα emission spectra and spectra of reference samples it is concluded that the CO 3 2− group in (C,N)Sr 2Ca n−1 Cu n O y and (Cu,C,N)Sr 2Ca n−1 Cu n O y is substituted by the NO 2 − instead of the NO 3 − group. This induces the creation of hole carriers in these compounds.

The formation of strontium analogues of YBa 2Cu 3O 7−x

The existence of materials of the type (Ln,Ce) 2Sr 2Cu 3O 8+x (Ln=lanthanide, Y), analogies of the unstable YSr 2Cu 3O 7−x 2 with yttrium replaced by a fluorite block, (Ln,Ce) 2O 2, have yet to confirmed by detailed structural studies. Reported here are the results of an investigation into their formation and structure which indicate the partial substitution of copper on the “Cu1” sites by cerium to be necessary to stabilise the YBCO-type strucure.

Thermally activated flux movement and critical transport current density in epitaxial Bi2Sr2CaCu2O8+ delta films.

In this article we report on thermally excited flux creep and the critical transport current density [ital j][sub [ital c]] in high-quality epitaxial Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8+[delta]] thin films. Both dissipative mechanisms are governed by the highly anisotropic behavior of this compound which was investigated by means of the angular dependence of the magnetoresistivity ([gamma][ge]150). The activation energy [ital U] for thermally excited flux creep was evaluated with respect to temperature, magnetic field, and applied current density [ital j]. [ital U]([ital T],[ital B],[ital j]) is essentially increasing linearly with falling temperature, power-law dependent on the field ([ital U][proportional to][ital B][sup [minus][alpha]] with [alpha][approx]0.5), and almost independent of current density for [ital j][le]10[sup 5] A/cm[sup 2]. These experimental results are consistent with the concept of plastic flux creep. The critical current density exhibits high absolute values [[ital j][sub [ital c]](77 K, [ital B]=0)=4[times]10[sup 5] A/cm[sup 2]] and was measured for magnetic fields in the configuration [bold B][parallel][ital c] up to 10 T and also with respect to various [Theta] angles between the [ital c] axis and field direction. The decrease of [ital j][sub [ital c]] with increasing [ital B] was found to be significantly reduced in comparison to single crystalsmore » and prior results on thin films. A further enhancement in the [ital j][sub [ital c]]([ital B],[ital T]) behavior could not be achieved by chemical doping through partial substitution of copper by zinc.« less

On the magnetic properties of cadmium-doped Y-Ba-Cu-O high-temperature superconductors

The discovery of the superconducting system Y B a C u O , with a transition temperature above 90 K [1], opened a new field of studies in the high-To superconductors° Substitution of yttrium by different rare-earth elements was found to influence the superconducting properties very weakly. Partial substitution of copper by different elements, especially by 3d transition-metal ions, has a strong effect on the superconducting properties of the material [2, 3]. Material doped with Cd was investigated recently by various researchers, and the results were not similar [4-6]. The main reason was the different method of preparation of the samples and the different dose of doping. In the present case the samples were prepared to have the nominal composition YBa2Cu3CdxOy and the first results were presented in a recent letter [6]. It was found that for x 0.2 CdO in excess was detected and the electrical behaviour above the transition temperature is a semiconductor-like one. The lattice parameters increase with Cd content up to the solubility limit, and decrease for x > 0.2. The best electrical characteristics were found for x -0.05. The resistivity of this material at room temperature decreases by at least two orders of magnitude, compared with the undoped material [7]. Positron annihilation measurements showed a lifetime component of about 320 ps, which has been attributed to some kind of defect complexes. A strong suppression of this component, after Cd insertion, suggests that Cd fills these defects preferentially [8]. In the present letter magnetic measurements, on Cd-doped Y B a C u O superconductors, are presented. The method of preparation of the YBa2Cu3CdxOy compounds is given in detail in a recent letter [6]. It must, however, be mentioned that instead of CuO powder, which was used by most researchers, CuzO powder was used as a starting material. This results in a different temperature of oxygen uptake during the annealing of the samples [7]. The d.c. magnetic moments were measured from 20 to 100 K by a Varian Foner-type vibrational

Phonon softening in the far-infrared spectra of YBa 2(Cu 1-xNi x) 3O 7

The reflectivity of YBa 2(Cu 1-xNi x) 3O 7 ceramics was measured as a function of temperature and the Ni concentration (x = 0.01, 0.03 and 0.05). The obtained spectra are presented in the range 260–340 cm −1 which contains the two out-of-plane modes of the CuO 2 plane showing the highest phonon softening. The modes at 280 and 310 cm −1 soften around 5–6 and 3 cm −1 , respectively, upon cooling of the samples from 300 to 10 K. The softening is almost independent of the Ni content and equivalent to the effect observed in undoped YBa 2Cu 3O 7. Contrary to Zn doping, these results show that a partial substitution of copper with magnetic Ni ion does not affect much the phonon softening and superconductivity in the YBaCuO system.