The Effect of Copper Substitutions and Preparation Conditions on the Critical Current of YBa2Cu3O7—δ Superconductors (original) (raw)
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Physica Status Solidi (a), 1993
A preparation process for YBalCu,O, (afterhere YBCO) superconducting ceramics is presented, in which partial substitution of the copper oxide component by metallic copper is used. The results of an investigation for improving the critical current in YBCO superconductors are also presented. These results show that the YBCO superconductors can be successfully prepared by using the partial metallic copper substitution process. The sintered superconducting ceramics all contain the same pure single phase. The critical current J , of these samples is linearly dependent on the substituted metallic copper content up to 50 wt%. For samples substituted with about 50 wtoh of the copper content J , is improved by a factor of about 1.5, i.e. J , > 300 A/cm2. The experimental values of J , measured at a temperature of 77 K and zero field show that J , is limited by the intergrain tunneling weak-link effect. The linear dependence of J , on the normal state tunneling resistance is in good agreement with the Ambegaokar-Baratoff theory. The energy gap of YBCO superconductors is estimated based on the Ambegaokar-Baratoff theory to be as high as 24 = 7.84kT.
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 ...
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.
2019
The aligned YBa2Cu3O7-δ(YBCO) superconducting materials were prepared by unique annealing method on a Gold foil. The structural and other properties of these superconducting materials have been studied i.e. X-ray diffraction, Scanning Electron Micrograph Magnetization and resistivity measurements. The study shows that the change in the Gold doping concentration in these superconducting materials from 0.1 to 3% affected the transition temperature range from 89K to 94K and the critical current density noticeably. The current density measured from the M-H curve is 2 × 104 Acm-2 by Bean Model. Densification and elongated alignment ≈200 µm longs are observed in these materials.
Resistive measurements of the inter- and intragranular critical current properties in YBa2Cu3O7−δ/Fe
Cryogenics, 1988
YBa2Cu307~ and Fe-(for Cu) substituted bulk samples were prepared by different methods, i e the direct and redirect powder metallurgical method and the citrate method The samples were charactenzed by magnet=zat~on measurements, X-ray diffract=on, TEM, SEM and EDX Four-probe resistive measurements were executed on the ceramic samples in order to obtain the superconducting transit=on temperature, T c, as well as the cnt=cal current density, Jc These data show the presence of two 'superconducting' phases, which can be shown to correspond to the rater-and mtragranular properties of the samples The res=stlve measurements yield a lower hmit of the Jc values and, therefore, complement magnet=zatlon data reported m the hterature Furthermore, the critical current dens=ty, Jc, =s related to the underlying microstructure and the chemical homogenmty of the sample, wh=ch both strongly depend on the preparat=on method and parameters In the Y-Ba cuprate superconductors larger cnt=cal currents are obtained upon the substitution of Cu by Fe and by the apphcatlon of the c=trate method, wh=ch guarantees an extremely homogeneous stoich~ometry
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.
physica status solidi (a), 2002
The influence of the quasi-equal partial substitution of non-magnetic (Y 3+ )/magnetic (Dy 3+ ) ions in YBa 2 Cu 3 O 7--y on the superconducting properties of the material has been investigated. To minimize the influence of the stress field induced by lattice mismatch, Dy-substituted YBa 2 Cu 3 O 7--y was studied because Y 3+ and Dy 3+ ions have similar ionic radii. The investigation was performed on polycrystalline and powder samples with general formula Dy x Y 1--x Ba 2 Cu 3 O 7--y (x ¼ 0.4-0.6). Higher magnetic losses and intragranular critical current density J c were observed for partially substituted samples in comparison with DyBCO. The strongest influence of magnetic substitution on the electrical resistivity properties was observed in the mixed state.
The effect of LiOH addition to the superconducting properties of YBa2Cu3O7-x
Journal of Superconductivity, 1997
The effect of LiOH addition to YBa2Cu3O7-x is presented. The crystal structure remains orthorhombic, but the orthorhombic splitting decreases from 0.0171 at 2 at. % Li to 0.0158 at 50 at. % Li. The critical temperature exhibits a decrease from 91.18 to 83.79 K in the same range of lithium concentrations. From the magnetization curves were obtained the lower critical fields and the intragranular critical current density. The latter exhibits a negative power law, jc ~ B -~, with a .~ 1/2. V-I characteristics are typical for grained superconducting materials: V<(I-L) ~8"~. The transport critical current dependence on temperature and magnetic field is also presented.
Improvement of the Superconducting Transport Properties of YBa2Cu3O7− δ by BaZrO3 Doping
Journal of superconductivity, 2001
We have doped the YBa 2 Cu 3 O 7−δ superconducting ceramics with BaZrO 3 up to 75 wt.% and studied the changes of some physical properties. The most important finding is the enhancement of the critical current density, which has a maximum at around 5 wt.% doping level. Compared with the undoped samples, the critical current density is four times higher if the doping compound is introduced prior to the calcination treatment, or two times higher if BaZrO 3 is introduced prior to the sintering treatment. The dependence of the critical current density on the doping level is consistent with the dependence of the Seebeck coefficient. We also observed a very small decrease of the critical temperature. The real density of the samples decreases with increasing doping level as expected from the ratio between the theoretical densities of YBa 2 Cu 3 O 7−δ and BaZrO 3 , the effect being important for doping levels higher than 25 wt.%. KEY WORDS: YBa 2 Cu 3 O 7−δ ; BaZrO 3 doping; transport properties.