SCALING BETWEEN LOCALIZATION LENGTH AND TC IN DISORDERED YBa2Cu3O6.9

1999 ◽  
Vol 13 (29n31) ◽  
pp. 3601-3604
Author(s):  
ANDREA GAUZZI ◽  
DAVOR PAVUNA
Keyword(s):  
Coherence Length ◽  
Localization Length ◽  
Charge Carriers ◽  
Superconducting Transition ◽  
Scaling Relation ◽  
X Ray Diffraction ◽  
Ginzburg Landau ◽  
X Ray ◽  
Structural Coherence ◽  
Superconducting Coherence Length

We quantitatively study the effect of growth-induced reduction of long range structural order on the superconducting transition in epitaxial YBa 2 Cu 3 O 6.9 films. The corresponding reduction of structural coherence length rc is determined from the width of X-ray diffraction rocking curves. Tc measurements in the films give evidence for the validity of the empirical scaling relation ΔTc~ rc,ab-2, where ΔTc is the disorder-induced reduction of Tc and rc,ab is the structural coherence length in the ab-plane. To explain this algebraic law we propose a simple phenomenological model based on the disorder-induced localization of the charge carriers within each ordered domain of size rc,ab. This picture enables us to precisely determine the Ginzburg-Landau superconducting coherence length in the ab-plane, and we obtain ξab=1.41±0.04 nm.

Local order in YBa2Cu3−yCoyO6+2x studied by anomalous diffuse x-ray scattering

1994 ◽  
Vol 9 (12) ◽  
pp. 3050-3058 ◽  
Author(s):  
H. Renevier ◽  
X.B. Kan ◽  
J.P. Quintana ◽  
K.J. Zhang ◽  
J.B. Cohen
Keyword(s):  
Coherence Length ◽  
Local Order ◽  
X Ray ◽  
Intensity Measurements ◽  
X Ray Scattering ◽  
Co Concentration ◽  
Structural Coherence ◽  
Superconducting Coherence Length ◽  
The Difference ◽  
Ray Scattering

The local order in a single crystal of YBa2Cu2.53Co0.47O7.13 has been studied with anomalous diffuse x-ray scattering. (For such a Co concentration the compound is nonsuperconducting.) Intensity measurements were carried out at two energies below the Co edge. The difference data could then be expressed in terms of the local structure around a Co atom. The short-range order parameters (α's) indicate that the Co and Cu atoms are nearly randomly distributed on the Cu1 sites. The estimated size of the Co-free “domains” is 5-7 Å. The first neighbor in-plane Co-Co distances are significantly shortened, indicating that the Co atoms are displaced from their average positions. The data also show a significant decrease of the Co-O1 distance, leading to an increase of the Cu2-O1 distance. The lengthening of the Cu2-O1 distance implies a lowering of the Cu2 formal valence. The Co substitution also affects the in-plane Cu2 positions. The present study shows that the Cu-O2 structural coherence is altered on a scale smaller than the superconducting coherence length. As far as the superconductivity is concerned, the Cu2 valence remains one of the most important parameters in determining the superconducting properties of the Co-doped 123 compounds. On the other hand, there is some evidence that in order for superconductivity to occur in this and other doped cuprate compounds, the size of dopant-free regions in the basal plane may have to exceed the superconducting coherence length.

Role of the Structure and Electronic Properties of Fe2O3-MoO3 Catalyst on the Dehydration of Isopropyl Alcohol

1993 ◽  
Vol 58 (7) ◽  
pp. 1591-1599 ◽  
Author(s):  
Abd El-Aziz A. Said
Keyword(s):  
Active Sites ◽  
Isopropyl Alcohol ◽  
Oxide Catalyst ◽  
Flow System ◽  
Charge Carriers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Catalyst Composition ◽  
Surface Active

Molybdenum oxide catalyst doped or mixed with (1 - 50) mole % Fe3+ ions were prepared. The structure of the original samples and the samples calcined at 400 °C were characterized using DTA, X-ray diffraction and IR spectra. Measurements of the electrical conductivity of calcined samples with and without isopropyl alcohol revealed that the conductance increases on increasing the content of Fe3+ ions up to 50 mole %. The activation energies of charge carriers were determined in presence and absence of the alcohol. The catalytic dehydration of isopropyl alcohol was carried out at 250 °C using a flow system. The results obtained showed that the doped or mixed catalysts are active and selective towards propene formation. However, the catalyst containing 40 mole % Fe3+ ions exhibited the highest activity and selectivity. Correlations were attempted to the catalyst composition with their electronic and catalytic properties. Probable mechanism for the dehydration process is proposed in terms of surface active sites.

scholarly journals Influence of Li2CO3 addition on electrical and magnetic properties of Ni0.6Mg0.4Fe2O4

2020 ◽  
Vol 10 (03) ◽  
pp. 2050003
Author(s):  
M. R. Hassan ◽  
M. T. Islam ◽  
M. N. I. Khan
Keyword(s):  
Magnetic Properties ◽  
Single Phase ◽  
Low Frequency ◽  
Solid State Reaction Method ◽  
Charge Carriers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Electrical And Magnetic Properties ◽  
Frequency Regime ◽  
Xrd Patterns

In this research, influence of adding Li2CO3 (at 0%, 2%, 4%, 6%) on electrical and magnetic properties of [Formula: see text][Formula: see text]Fe2O4 (with 60% Ni and 40% Mg) ferrite has been studied. The samples are prepared by solid state reaction method and sintered at 1300∘C for 6[Formula: see text]h. X-ray diffraction (XRD) patterns show the samples belong to single-phase cubic structure without any impurity phase. The magnetic properties (saturation magnetization and coercivity) of the samples have been investigated by VSM and found that the higher concentration of Li2CO3 reduces the hysteresis loss. DC resistivity increases with Li2CO3 contents whereas it decreases initially and then becomes constant at lower value with temperature which indicates that the studied samples are semiconductor. The dielectric dispersion occurs at a low-frequency regime and the loss peaks are formed in a higher frequency regime, which are due to the presence of resonance between applied frequency and hopping frequency of charge carriers. Notably, the loss peaks are shifted to the lower frequency with Li2CO3 additions.

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.

ITO Thin Films on Silicon Buffer by Sol Gel Method

2006 ◽  
Vol 514-516 ◽  
pp. 1155-1160 ◽  
Author(s):  
Talaat Moussa Hammad
Keyword(s):  
Thin Films ◽  
Indium Tin Oxide ◽  
Optical Transmission ◽  
Sol Gel ◽  
Precursor Solution ◽  
Charge Carriers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ito Thin Films ◽  
Uv Visible

Sol gel indium tin oxide thin films (In: Sn = 90:10) were prepared by the sol-gel dipcoating process on silicon buffer substrate. The precursor solution was prepared by mixing SnCl2.2H2O and InCl3 dissolved in ethanol and acetic acid. The crystalline structure and grain orientation of ITO films were determined by X-ray diffraction. The surface morphology of the films was characterized by scanning electron microscope (SEM). Optical transmission and reflectance spectra of the films were analyzed by using a UV-visible spectrophotometer. The transport properties of majority charge carriers for these films were studied by Hall measurement. ITO thin film with electrical resistivity of 7.6 ×10-3 3.cm, Hall mobility of approximately 2 cm2(Vs)-1 and free carrier concentration of approximately 4.2 ×1020 cm-3 are obtained for films 100 nm thick films. The I-V curve measurement showed typical I-V characteristic behavior of sol gel ITO thin films.

Preparation of YBCO Superconducting Films by Sol-Gel Process

2007 ◽  
Vol 546-549 ◽  
pp. 2007-2010
Author(s):  
Gao Yang Zhao ◽  
Huang Li Zhang ◽  
Ren Zhong Xue ◽  
Yuan Qing Chen ◽  
Li Lei
Keyword(s):  
Sol Gel ◽  
Precursor Solution ◽  
Superconducting Films ◽  
Superconducting Transition ◽  
X Ray Diffraction ◽  
Organic Salts ◽  
Ybco Films ◽  
X Ray ◽  
Sol Gel Process ◽  
Ybco Superconducting Films

precursor solution was prepared using barium trifluoroacetae (Ba-TFA) and non-fluorine yttrium (Y) and copper (Cu) organic salts. The precursor solution was modified by benzalacetone (BzAcH), in which the Cu2+ were chelated with BzAcH, which preventing the loss of Cu in the pyrolysis process. Dense YBCO superconducting films with smooth surface, which confirmed by scanning electron microscopy (SEM), were repeatedly obtained through sol-gel process. X-ray diffraction (XRD) 2θ scanning and φ scanning indicated that the as-prepared YBCO films had good c-axis texture. YBCO films with superconducting transition temperature (TC) above 89K were obtained.

X-ray Diffraction Study of Amorphous NixZr(100-x)-Alloys Prepared by Melt-Spinning

1991 ◽  
Vol 46 (11) ◽  
pp. 947-950
Author(s):  
W.-M. Kuschke ◽  
P. Lamparter ◽  
S. Steeb
Keyword(s):  
Melt Spinning ◽  
Pair Correlation ◽  
Nickel Concentration ◽  
Superconducting Transition ◽  
X Ray Diffraction ◽  
X Ray ◽  
Coordination Numbers ◽  
Structure Factors ◽  
Wide Range ◽  
Good Agreement

AbstractAmorphous Ni-Zr-alloys can be prepared by melt-spinning within a wide range of composition. Studies by X-ray diffraction yielded structure factors, pair correlation functions, total coordination numbers and atomic distances in dependence on the nickel concentration in the range of 25 up to 45 atomic percent. The change of the total coordination number and atomic distances turned out to be linear with the composition in this range. This is in good agreement with the linear composition dependence of the superconducting transition temperature, magnetic susceptibility, crystallization temperature, and electrical resistivity in the investigated range of composition.

Structure and properties of solid solutions in the Mg-Al-B system

Open Physics ◽  
2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Ludmila Sevastyanova ◽  
Olga Gulish ◽  
Vladimir Stupnikov ◽  
Vladimir Genchel ◽  
Oleg Kravchenko ◽  
...  
Keyword(s):  
Solid Solutions ◽  
Unit Cell ◽  
Superconducting Transition ◽  
Structure And Properties ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Resistivity Measurements ◽  
Ceramic Synthesis

AbstractCompounds with the general formula Mg1−x AlxB2 were obtained by two-step ceramic synthesis. All compounds were characterized by X-ray diffraction, NMR spectroscopy, and by four point probe resistivity measurements in various magnetic fields method. The diborides unit cell parameters were determined as a function of the Al mole fraction. With the vaues of x up to 0.40 (where x is the composition of the stock prepared for sintering), the unit cell parameters of Mg1−x AlxB2 are similar to those of pure MgB2 and the superconducting transition temperature was lowered. For stock compositions of 0:25 ≤ x ≤ 0:60, the products contain a superstructure, also superconducting phase, which becomes the only product at x = 0:50, and at x > 0:60 this phase is replaced by AlB2-based solid solutions.

Powder X-Ray Diffraction Data for the Superconducting Phase TlCaBa2Cu2O7−δ

1992 ◽  
Vol 7 (2) ◽  
pp. 115-116 ◽  
Author(s):  
Terry L. Aselage ◽  
Michael O. Eatough
Keyword(s):  
Cuprate Superconductors ◽  
General Interest ◽  
Superconducting Transition ◽  
X Ray Diffraction ◽  
Pure Compound ◽  
Group 14 ◽  
X Ray ◽  
Superconducting Phases ◽  
The Family ◽  
Unit Cells

High temperature superconducting phases in the Tl-Ca-Ba-Cu-O system are ideally represented by the formula TlmCan−1Ba2CunO2(n+1)+m, with m either 1 or 2 and n = 1 to at least 3 (Parkin et at., 1988). Each of these phases contains one or more of the nearly planar CuO2sheets common to the cuprate superconductors. A single Ca atom separates adjacent CuO2sheets (n > 1). Single or double rock salt-like Tl-O layers are separated from the Can−1CunO2nregions by single Ba-O layers. Each of the Ca-containing members of this family crystallizes in a tetgragonal unit cell, with space group 14/mmm for the m = 2 series and P4/mmm for the m = 1 series.Despite the general interest in this family of superconductors, little has been reported about the m = 1, n = 2 member, TlCaBa2Cu2O7−δ, hereafter called 1122. This lack of work is due at least in part to the difficulty in synthesizing the pure compound (Michel et at., 1991). Additionally, technological interest has focused on members of the family with higher superconducting transition temperatures, particularly Tl2Ca2Ba2Cu3Oywith Tcup to 125 K. The critical temperature of 1122 has been reported from as low as 50 K (Hervieu et al., 1988) to as high as 103 K (Morosin et al., 1988), and at several values in between (Ganguli et al., 1988; Liang et al., 1988). Most of the samples had other superconducting phases in addition to 1122. Because of the nearly identical a axis lengths of the unit cells of the Tl-family of superconductors, syntactic intergrowths may be present in such multiphase samples.

Superconductivity of Dc Reactive Magnetron Sputtered Epitaxial TiN/NbN Superlattices

1992 ◽  
Vol 275 ◽  
Author(s):  
M. Shinn ◽  
B. -S. Hong ◽  
S. A. Barnett
Keyword(s):  
Magnetic Field ◽  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Film Surface ◽  
Wavelength Dependence ◽  
Reactive Magnetron ◽  
Superconducting Transition ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron

ABSTRACTEpitaxial B1-structure TiN/NbN superlattices have been grown by reactive magnetron sputtering On MgO(001). X-ray diffraction and transmission electron microscopy (TEM) diffraction spectra exhibited up to nine orders of superlattice reflections, indicating that the superlattice interfaces were relatively sharp. TEM images also showed well-defined layers. The superlattice wavelength (∧) dependence of the superconducting transition temperature (Tc), critical Current density (Jc), and electrical resistivity (ρ) have been investigated. Tc values increased from 12 K to 17 K with increasing ∧. Jc in a magnetic field perpendicular to the film surface ranged from 104 to 106 A/cm2, increasing with increasing wavelength and decreasing with increasing applied magnetic field. Jc in a field parallel to the film surface was > 10 times higher, ≈ 107 A/cm2. The resistivity exhibited different ∧ dependencies in three different A ranges.

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