Microstructural and Superconducting Properties of YBa_2Cu_{3-x}Co_xO_{7-\delta} System (original) (raw)
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Microstructural and Superconducting Properties of YBa2Cu3-xCoxO7-δ System
Integrated Ferroelectrics, 2011
Bulk superconductor samples of YBa2Cu3-xCoxO7-δ with x = 0, 0.01, 0.03, 0.05 are synthesized by solid-state reaction route. Both x-ray diffraction and electron microscopy have been employed to study the phase identification, intergrowths, dislocations and the local structure of these samples. Transition temperature of the samples has been determined by four probe resistivity measurements. The x-ray diffraction patterns indicate that the gross structure/phase of YBa2Cu3-xCoxO7-δ do not change with the substitution of Co up to x = 0.05. The zero resistance critical transition temperature [Tc(R = 0)] is found to decrease and critical current density (Jc) increases with the increased concentration of cobalt in the compound. The Jc enhancement for the cobalt doped samples may be resulting due to flux pinning from some defects such as planar defects, stacking faults and micro defects (twin, domains etc.) and the rapid suppression in Tc may be due to the cooper pair breaking and the hole filling in the CuO2 planes.
Investigation of physical and structural properties of cs doped y1ba2cu3o7 superconductors
Cumhuriyet Science Journal, 2021
In this work, YBa2‑xCsxCu3O7‑δ (x= 0.05, 0.1, 0.2 and 0.3 wt. %) samples were prepared by using solid state reaction method. Some electrical, physical and structural properties of these compounds were examined by using SEM (scanning electron microscopy), XRD (X-ray diffraction), electrical resistivity, critical current density and AC susceptibility measurements, respectively. On the basis of the SEM measurements, it would seem that increasing the amount of Cs doping, the porous structures decrease and the grain size increases up to approximately 50 μm. Unit cell parameters were calculated by employing XRD measurements. On the basis of the data obtained from X-ray diffraction, Cs atoms displaced Ba atoms in the crystal structure. From the measurements of electrical resistivity at 80 K-120 K temperature, it was determined that the highest transition temperature was 91.5 K after addition of 0.05 wt. % Cs. The critical transition temperature was decreased by increasing the amount of Cs ...
Oxygen content, microstructure, and superconductivity of YBa2Cu3O7− x
Journal of Materials Research, 1987
The influence of preparation conditions and microstructure on the superconductive properties of single-phase poly-crystalline YBa2Cu3O7 _ x was investigated by electron probe microanalysis, transmission electron microscopy (TEM), and x-ray powder diffraction as a function of temperature in various ambients supplemented by resistivity and susceptibility measurements. Leaching of Ba was observed when samples were brought in contact with water. The TEM imaging revealed that individual grains have an extremely defect-rich outer shell and an inner core with a domain structure with a and b axes interchanged. The transition temperature Tc was found to decrease with increasing quench temperature in the range 400-900 °C. The Tc was observed to be linearly proportional to the difference in the orthorhombic cell parameters (b-a). Further implications are discussed.
Superconducting Properties of Y(Ba1-xCax)2Cu3O7-delta (0
A series of polycrystalline compounds with a nominal composition of Y(Ba 1-x Ca x ) 2 Cu 3 O 7-δ (0 ≤ x ≤ 0.05) had been synthesized using solid state reaction method. Crystal structure of those samples was characterized by Rietveld refinement on the x-ray powder diffraction data. It was found that the structural parameters were not changed appreciably with Ca content in Y(Ba 1-x Ca x ) 2 Cu 3 O 7-δ . While c-axis remained almost unchanged, both a and b axes decreased slightly leading to the decrease in orthorhombicity of Y-123 phase. The superconducting transition temperature, T c was determined by measuring the change of electrical resistance versus temperature (50 K -300 K) using a four point probe technique. The T c
Journal of Applied Physics, 2005
Results of phase formation, resistivity (ρ), and thermoelectric power (S), are reported on Y1−xCaxBa2Cu2.7Co0.3O7 compounds with x=0.1 and 0.2. Pristine compound, i.e., without Co or Ca substitution crystallizes in orthorhombic structure with space-group P∕mmm. The Cu-site Co substituted compound, i.e., YBa2Cu2.7Co0.3O7 is tetragonal. With simultaneous doping of Ca at the Y site in Co substituted compound, i.e., Y1−xCaxBa2Cu2.7Co0.3O7 the tetragonal nature still remains. ρ(T) measurements showed superconducting transition temperature (Tc) to decrease from 90K (YBa2Cu3O7) to 33K for YBa2Cu2.7Co0.3O7, which with further Ca substitution increases from 33to53K (Y0.9Ca0.1Ba2Cu2.7Co0.3O7) and 67K for Y0.8Ca0.2Ba2Cu2.7Co0.3O7. Tc decreases first with Cu-site Co substitution by hole filling and later recovers by simultaneous hole creation by Y site Ca substitution. Room temperature thermoelectric power S (300K), which is an indirect measure of mobile carriers shows the decrease of carriers ...
Synthesis and characterization of YBa2Cu3O7−x. Superconducting materials
Materials Research Bulletin, 1988
YBa2Cu307. X superconducting materials have been obtained from oxalate coprecipitation and metalloorganic decomposition. Resistivity and magnetic measurements confirm the superconducting behavior below 90 K. Calorimetric measurements reveal the role of impurities in the specific heat evolution.
Structural behavior and superconductivity of YBa2Cu3Ox
Solid State Communications, 1987
The compound YBa&+Ox was given various oxidation treatments over a range of oxygen pressures from 0.02 to 200 MPa and temperatures up to 1223K. A tetragonal to orthorhombic phase transformation was observed, leading to superconducting behavior below 94K. The orthorhombic unit cell parameters (i.e. volume, bond lengths, and axial distortions) were found to correlate with the superconducting transition temperatures. These correlations are rationalized in terms of the interrelationship of oxygen stoichiometry with the lattice parameters of the orthorhombic phase. The nature of superconductivity in YBa$u,O, and LazCuO, is related to the Cu-0 coordination polyhedra and an explanation is proposed for the observed multiple superconducting transitions in YBa$u,O,.
Physica C: Superconductivity, 2005
We report systematic studies of structural, microstructural and transport properties of Y 1-x Ca x Ba 2 Cu 3 O 7-δ bulk samples with 0.20 ≥ x ≥ 0.0. The partial substitution of Ca 2+ at Y 3+ site in YBa 2 Cu 3 O 7-δ leads towards slightly overdoped regime, which along with disorder in CuO 2 planes is responsible for decrease in superconducting transition temperature (T c ) of the doped system. The microstructural variants being studied by transmission electron microscopy (TEM) technique in imaging and selected area diffraction modes revealed an increase in the density of twins with increase in Ca concentration despite the fact that there is slight decrease in the orthorhombicity. This is against the general conviction of decrease in twin density with decreasing orthorhombicity. An increase in twin density results in sharpening of twin boundaries with increasing Ca concentration. These sharpened twin boundaries may work as effective pinning centers. A possible correlation between microstructural features and superconducting properties has been put forward and discussed in the present investigation.
Investigation of Lu effect on YBa2Cu3O7−δ superconducting compounds
Journal of Materials Science: Materials in Electronics, 2012
This study reports the effect of Lu addition on the microstructural and superconducting properties of YBa 2 Lu x Cu 3 O 7-d (Y123) superconducting samples with x = 0, 0.1, 0.3, 0.5 and 0.7 by means of X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), electron dispersive X-ray (EDX), electrical resistivity and transport critical current density (J c) measurements. The samples prepared by the liquid ammonium nitrate and derivatives are exposed to various annealing time (20, 40 and 60 h) and temperature (950, 960 and 970°C), and the best ambient for the sample fabrication is determined to be 970°C for 20 h. Zero resistivity transition temperatures (T c), critical current densities (J c), variation of transition temperatures, hole-carrier concentration, grain size, lattice parameter, surface morphology, element distribution, crystallinity and resistivity (at room temperature) values of the bulk superconducting samples prepared at 970°C for 20 h are compared with each other. T c and J c values of the samples are inferred from the dc resistivity and the critical current measurements, respectively. The results show that the T c value of the pure sample is about 90.6 K while the sample doped with 0.1 wt% Lu has the maximum T c value (92.5 K). However, beyond x = 0.1, the T c value is observed to decrease toward to 83.5 K with increment in the Lu addition. Similarly, the J c values measured are found to reduce from 142 to 76 A/cm 2 with the addition. Moreover, XRD measurements show that both pure and Lu-doped samples exhibit the polycrystalline superconducting phase with the changing intensity of diffraction lines and contain Y123 and Y211 phase, confirming the incorporation of Lu atoms into the crystalline structure of the samples studied. At the same time, comparing of the XRD patterns of samples, the intensity ratio of the characteristic (110) and (013) peaks on the sample doped with 0.1 wt% Lu is more than that on the other samples prepared. Additionally, SEM images display that the sample doped with 0.1 wt% Lu obtains the best crystallinity, grain connectivity and largest grain size whereas the worst surface morphology is observed for the maximum doped sample (x = 0.7). Further, EDX results demonstrate that the Lu atoms doped are successfully introduced into the microstructure of the Y123 samples studied and the maximum Cu element level is observed for the sample doped with 0.1 wt%, explaining that why this sample obtains the best superconducting properties compared to others. According to all the results obtained, it is concluded that the 0.1 wt% Lu addition into the Y123 system improves the microstructural and superconducting properties of the samples studied.
Effect of Co-Ga Paired Substitution on Superconductivity in YBa2Cu3O7-delta
Modern Physics Letters B, 2004
The effect of Co-Ga paired substitution on the superconducting properties of YBa2Cu3O7-δ (Y-123) has been investigated by X-ray diffraction, ac susceptibility, dc resistivity and oxygen content measurements. We report in this paper the results of our studies on the paired substitution of a magnetic and non-magnetic ion at Cu site in Y-123, while keeping the total dopant concentration fixed. The simultaneous substitution of Co and Ga at Cu site shows variation in the transition temperature (Tc), oxygen content and hole concentration as a function of change in the balance of magnetic (Co) and non-magnetic (Ga) concentration. Orthorhombicity (D), given as (b-a)/a, also varies as a function of increasing dopant concentration. The variation in Tc due to Co-Ga substitution is discussed in the light of dopant valency and hole filling mechanism.