OXIDE SUPERCONDUCTIVITY RESEARCH AT NORTHWESTERN UNIVERSITY

1987 ◽  
Vol 01 (03n04) ◽  
pp. 829-829
Author(s):  
J.B. KETTERSON
Keyword(s):  
Electrical Transport ◽  
Short Review ◽  
Argon Atmosphere ◽  
Oxide Superconductors ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transport Studies ◽  
Wide Range ◽  
Northwestern University ◽  
Zero Resistance

A short review was presented of a wide range of activities involving the high Tc oxide superconductors at the Northwestern University. Calculations of the charge density associated with the d9 shell of the copper atom in the Cu-O planes and the d8 shell of the copper atoms along the Cu-O lines of the unit cell of YBa2Cu3O7 performed by Freeman, Massida and Yu were presented. Results of a detailed study of the pseudoternery phase diagram involving CuO, BaO and YO1.5 were shown which verify the existence of three compounds having the Y:Ba:Cu ratios 123 (the high Tc superconductor), 211 (the so-called green phase) and 132 (a new insulating compound). This work, performed by Mason and coworkers, involved X-ray diffraction, optical spectroscopy, magnetic susceptibility, and electrical transport studies. Transport measurements by Poeppelmeier, Song, Hwu and coworkers on the assembledges YBaSrCu3O7 anf YBa2Cu3O5F2 were reported; no evidence of superconducting behavior at temperatures above 90K was seen in the latter. A detailed study of the magnetic and transport properties of the YBa2−xLaxCu3−xNixO7±δ system was reported. For small Ni concentration (x<0.3) a continuous drop in Tc was observed. For x= 0.4 and 0.5 evidence of two separate transitions, near 75K and 25K, were seen in the resistance (with the resistance going to zero at about 15K); for x=0.7 semiconducting behavior was observed. A continuous drop in the normalized diamagnetic signal was seen with increasing x with the diamagnetic fraction being below 5 % for x=0.7 and above. X-ray diffraction showed a continuous decrease in the orthorhombic fraction and an increase in the tetragonal fraction with increasing x. Results on d.c. magnetron sputtering of thin films on MgO from a stoichiometric 123 target in an argon atmosphere were shown. With proper annealing films with onset temperature of 90K and zero resistance at 68K have been prepared; this work was done by Jin, Lee, Song and coworkers. A brief report on the effect of O-stoichiometry on EPR and susceptibility measurements in the 123 compound performed by Hoffman and coworkers and NMR in the La2−xSrxCuO4 compound by Halpern and coworkers was presented.

Transport Properties of Bi-related Nanowire Systems

2001 ◽  
Vol 635 ◽  
Author(s):  
Y. M. Lin ◽  
S. B. Cronin ◽  
J. Y. Ying ◽  
J. Heremans ◽  
M. S. Dresselhaus
Keyword(s):  
Electrical Transport ◽  
Lattice Structure ◽  
X Ray Diffraction ◽  
Localization Transition ◽  
X Ray ◽  
3D Localization ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Alloy Nanowires ◽  
Magneto Resistance

AbstractWe present here an electrical transport property study of Te-doped Bi nanowires, and Bi1−xSbx alloy nanowires embedded in a dielectric matrix. The crystal structure of the nanowires were characterized by X-ray diffraction measurements, indicating that the nanowires possess the same lattice structure as bulk Bi in the presence of a small amount of Te or Sb atoms. The resistance measurements of 40-nm Te-doped Bi nanowires were performed over a wide range of temperature (2 K≤ T ≤ 300 K), and the results are consistent with theoretical predictions. The 1D-to-3D localization transition and the boundary scattering effect are both observed in magneto-resistance measurements of Bi1−xSbx alloy nanowires at low temperatures (T < 4 K).

ANALYSIS OF FLUCTUATION CONDUCTIVITY OF GRANULAR Gd1-xPrxBa2Cu3O7-δ SUPERCONDUCTOR

2010 ◽  
Vol 24 (24) ◽  
pp. 2465-2475 ◽  
Author(s):  
CRISTIANO SANTOS LOPES ◽  
LINCOLN BRUM DE LEITE GUSMÃO PINHEIRO ◽  
MARCELO DOS SANTOS ◽  
ALCIONE ROBERTO JURELO ◽  
ROSÂNGELA MENEGOTTO COSTA ◽  
...  
Keyword(s):  
Critical Temperature ◽  
Electrical Transport ◽  
Single Phase ◽  
Transition Width ◽  
X Ray Diffraction ◽  
Solid State Reaction Technique ◽  
Fluctuation Conductivity ◽  
X Ray ◽  
Zero Resistance ◽  
Resistance State

Single phase polycrystalline Gd 1-x Pr x Ba 2 Cu 3 O 7-δ (0 ≤ x ≤ 0.10) samples have been prepared by standard solid state reaction technique and characterized by SEM, X-ray diffraction and electrical transport experiments. The samples were granular and homogeneous. It was observed that the critical temperature decreases and that the transition width increases with increasing Pr doping. Systematic measurements of fluctuation conductivity are reported. Special attention is taken above the critical temperature, where Gaussian and critical regimes are observed. Below the critical temperature, on approaching the zero resistance state, our results show a power-law behavior consistent with a phase transition from a paracoherent to a coherent state of the granular array.

CVD-Growth of Thin-Film Layered Se-Carbon Compounds

1996 ◽  
Vol 453 ◽  
Author(s):  
L. Grigorian ◽  
S. Fang ◽  
G. Sumanasekera ◽  
A. M. Rao ◽  
L. Schraderi ◽  
...  
Keyword(s):  
Thin Film ◽  
Raman Scattering ◽  
Electrical Transport ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transport Studies ◽  
Carbon Compounds ◽  
Oriented Films ◽  
Cvd Growth ◽  
Quartz Tubes

AbstractOriented films of layered Se-carbon compounds are grown on Ni substrates in evacuated sealed quartz tubes. Results of X-ray diffraction, Raman scattering and the c-axis electrical transport studies are reported. A discussion of possible models for the carbon -Se interaction is presented.

scholarly journals Multidimensional Ln-Aminophthalate Photoluminescent Coordination Polymers

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1786
Author(s):  
Carla Queirós ◽  
Chen Sun ◽  
Ana M. G. Silva ◽  
Baltazar de Castro ◽  
Juan Cabanillas-Gonzalez ◽  
...  
Keyword(s):  
Water Content ◽  
Coordination Polymers ◽  
Metal Ion ◽  
Low Cost ◽  
Microwave Assisted Synthesis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Wide Range ◽  
Ft Ir ◽  
Ft Ir Spectroscopy

The development of straightforward reproducible methods for the preparation of new photoluminescent coordination polymers (CPs) is an important goal in luminescence and chemical sensing fields. Isophthalic acid derivatives have been reported for a wide range of applications, and in addition to their relatively low cost, have encouraged its use in the preparation of novel lanthanide-based coordination polymers (LnCPs). Considering that the photoluminescent properties of these CPs are highly dependent on the existence of water molecules in the crystal structure, our research efforts are now focused on the preparation of CP with the lowest water content possible, while considering a green chemistry approach. One- and two-dimensional (1D and 2D) LnCPs were prepared from 5-aminoisophthalic acid and Sm3+/Tb3+ using hydrothermal and/or microwave-assisted synthesis. The unprecedented LnCPs were characterized by single-crystal X-ray diffraction (SCRXD), powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM), and their photoluminescence (PL) properties were studied in the solid state, at room temperature, using the CPs as powders and encapsulated in poly(methyl methacrylate (PMMA) films, envisaging the potential preparation of devices for sensing. The materials revealed interesting PL properties that depend on the dimensionality, metal ion, co-ligand used and water content.

STUDY OF THE DEPENDENCE OF HIGH Tc ON VARIOUS SINTERING TEMPERATURES FOR Bi-Pb-Sr-Ca-Cu-O SUPERCONDUCTORS

1991 ◽  
Vol 05 (24n25) ◽  
pp. 1635-1638
Author(s):  
S.M. M.R. NAQVI ◽  
A.A. QIDWAI ◽  
S.M. ZIA-UL-HAQUE ◽  
FIROZ AHMAD ◽  
S.D.H. RIZVI ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Liquid Nitrogen ◽  
X Ray Diffraction ◽  
High Tc ◽  
X Ray ◽  
Resistivity Measurements ◽  
Zero Resistance

Bi1.7-Pb0.3-Sr2-Ca2-Cu3-Ox superconducting samples were prepared at 855°C, 862 C, 870 C, and 882 C sintering temperatures respectively. All samples were sintered for 120 hours. The samples were then quenched in liquid nitrogen. The electrical resistivity measurements showed that the samples sintered at 870° C had the best Tc. For these samples the Tc onset was around 120 K and the zero resistance was obtained at 108 K. X-ray diffraction studies showed that the samples were multiphased.

2D X-ray diffraction and molecular modelling of the crystalline structure of polyesters under uniaxial stress

2021 ◽  
pp. 096739112199822
Author(s):  
Ahmed I Abou-Kandil ◽  
Gerhard Goldbeck
Keyword(s):  
Crystalline Structure ◽  
Molecular Modelling ◽  
Three Dimensional ◽  
Uniaxial Stress ◽  
X Ray Diffraction ◽  
X Ray ◽  
Wide Range ◽  
Modelling Techniques ◽  
Diffraction Patterns

Studying the crystalline structure of uniaxially and biaxially drawn polyesters is of great importance due to their wide range of applications. In this study, we shed some light on the behaviour of PET and PEN under uniaxial stress using experimental and molecular modelling techniques. Comparing experiment with modelling provides insights into polymer crystallisation with extended chains. Experimental x-ray diffraction patterns are reproduced by means of models of chains sliding along the c-axis leading to some loss of three-dimensional order, i.e. moving away from the condition of perfect register of the fully extended chains in triclinic crystals of both PET and PEN. This will help us understand the mechanism of polymer crystallisation under uniaxial stress and the appearance of mesophases in some cases as discussed herein.

COMPOSITION DEPENDENCE OF SUPERCONDUCTIVITY AND CRYSTAL STRUCTURE IN La(Ba1−xCax)2Cu3O7−y SYSTEM

1989 ◽  
Vol 03 (04) ◽  
pp. 307-311 ◽  
Author(s):  
N. CAO ◽  
J.Q. ZHENG ◽  
X.Y. SHAO ◽  
X.S. CHEN ◽  
W.Y. GUAN
Keyword(s):  
Crystal Structure ◽  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
Composition Dependence ◽  
Superconducting Transition ◽  
Orthorhombic Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Resistivity Measurements ◽  
Zero Resistance

The composition dependence of superconductivity and crystal structure in La ( Ba 1−x Ca x)2 Cu 3 O 7−y system was determined by the resistivity measurements and X-ray diffraction analysis. The superconducting transition temperature is raised with the increase of Ca content till x=0.6, at which the zero resistance temperature of the sample is 81.5 K. In the meanwhile, the crystal structure of the sample changed from tetragonal (x=0) to orthorhombic structure (x=0.2, 0.4, 0.6). With further increase of Ca content, the superconductivity decrease for the sample of x=0.8 with mixed phases including the orthorhombic oxygen-deficient perovskite-like (ODP) structure and no superconducting transition is found at 4.2 K for the sample of x=1 without the ODP structure. A possible explanation of these experimental results is given.

Characterization of hydrofluoric acid treated Y–Ba–Cu–O oxides

1989 ◽  
Vol 4 (6) ◽  
pp. 1320-1325 ◽  
Author(s):  
Q. X. Jia ◽  
W. A. Anderson
Keyword(s):  
Hydrofluoric Acid ◽  
Electron Spectroscopy ◽  
Auger Electron ◽  
Surface Passivation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Zero Resistance ◽  
Reaction With Water ◽  
Scanning Electron

Effects of hydrofluoric acid (HF) treatment on the properties of Y–Ba–Cu–O oxides were investigated. No obvious etching of bulk Y–Ba–Cu–O and no degradation of zero resistance temperature were observed even though the oxides were placed into 49% HF solution for up to 20 h. Surface passivation of Y–Ba–Cu–O due to HF immersion was verified by subsequent immersion of Y–Ba–Cu–O in water. A thin layer of amorphous fluoride formed on the surface of the Y–Ba–Cu–O during HF treatment, which limited further reaction between Y–Ba–Cu–O and HF, and later reaction with water. Thin film Y–Ba–Cu–O was passivated by HF vapors and showed no degradation in Tc-zero after 30 min immersion in water. The properties of the surface layer of Y–Ba–Cu–O oxide after HF treatment are reported from Auger electron spectroscopy, x-ray diffraction, and scanning electron microscopy studies.

Structural Evaluation of Ti-22.2Si-11.1B Powders Milled with PCA Addition

2008 ◽  
Vol 591-593 ◽  
pp. 147-153
Author(s):  
Gilbert Silva ◽  
Erika Coaglia Trindade Ramos ◽  
N.S. da Silva ◽  
Alfeu Saraiva Ramos
Keyword(s):  
Electron Microscopy ◽  
Ball Milling ◽  
Ball Mill ◽  
Milling Process ◽  
Argon Atmosphere ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structural Evaluation ◽  
Equilibrium Structures ◽  
Scanning Electron

A large amount of the Ti6Si2B compound can be formed by mechanical alloying and subsequent heat treatment from the elemental Ti-22.2at%Si-11.1at%B powder mixture, but the yield powder after ball milling is reduced due to an excessive agglomeration of ductile particles on the balls and vial surfaces. This work reports on the structural evaluation of Ti-22.2at%Si-11.1at%B powders milled with PCA addition, varying its amount between 1 and 2 wt-%. The milling process was carried out in a planetary ball mill under argon atmosphere, and the milled powders were then heated at 1200oC for 1h under Ar atmosphere in order to obtain equilibrium structures. Samples were characterized by X-ray diffraction, scanning electron microscopy, and thermal analysis. Results revealed that the PCA addition reduced the excessive agglomeration during the ball milling of Ti-22.2at-%Si-11.1at-%B powders. After heating at 1200oC for 1h, the Ti5Si3, Ti3O and/or Ti2C phases were preferentially formed in Ti-22.2at%Si-11.1at%B powders milled with PCA addition, and the Ti6Si2B formation was inhibited.

EXPERIMENTAL STUDY OF THE HIGH Tc SUPERCONDUCTOR Y-Ba-Cu-O SYSTEM

1989 ◽  
Vol 03 (08) ◽  
pp. 661-664
Author(s):  
S.M.M.R. NAQVI ◽  
JAWAID ALAM ◽  
FIROZ AHMAD ◽  
MUSHEER HASAN KHAN
Keyword(s):  
Experimental Study ◽  
Superconducting Phase ◽  
X Ray Diffraction ◽  
High Tc ◽  
X Ray ◽  
High Tc Superconductor ◽  
Zero Resistance

Two batches of Y-Ba-Cu-O superconductors have been prepared. The zero resistance temperature is 90 K with Tc onset at 93 K and 95 K, respectively. Susceptibility measurements show superconducting phase at LN2. X-ray diffraction results indicates single phases.

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