Mechanism of Je Enhancement of YBa2Cu3O7-α Due to Ag-Doping

1987 ◽  
Vol 99 ◽  
Author(s):  
J. H. Kung ◽  
H. H. Yen ◽  
Y. C. Chen ◽  
C. M. Wang ◽  
P. T. Wu
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Crystal Orientation ◽  
Superconducting Phase ◽  
Optimum Level ◽  
Chemical Forms ◽  
Ag Doping ◽  
Ceramic Superconductors

ABSTRACTAg-doping was found to enhance the critical current density of the ceramic superconductors by as much as a factor of 15. This Jc enhancement is due to both the increased amount of the superconducting phase and the resulting preferred crystal orientation. The optimum level of dopant may vary according to the chemical forms of Ag dopants.

Effects of Ag doping on the critical current density of YBa2Cu3O7−y

1989 ◽  
Vol 69 (11) ◽  
pp. 1067-1071 ◽  
Author(s):  
Su Zhen-peng ◽  
Zhao Yong ◽  
Sun Shi-fang ◽  
Chen Zu-yao ◽  
Chen Xian-hui ◽  
...  
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Ag Doping

Effects of Tin Addition to the Tl-Based 1223 Superconducting System

1998 ◽  
Vol 12 (04) ◽  
pp. 131-141 ◽  
Author(s):  
Y. T. Wang ◽  
A. M. Hermann
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Temperature Drop ◽  
Superconducting Phase ◽  
Transport Critical Current Density ◽  
X Ray Diffraction ◽  
Pinning Centers ◽  
Magnetization Data ◽  
A Minor

Polycrystalline samples of Tl-based-1223 superconducting system were prepared with tin-addition to form ( Tl 0.5 Pb 0.5) Sn x Sr 1.6 Ca 2.4 Cu 3 O y, for x=0–0.3. X-ray diffraction data showed the presence of a minor 1212 phase and impurities which increased with increasing x while the samples without addition of tin, x=0, were nearly single phase of Tl,Pb-1223. The effects of tin addition to Tl,Pb-1223 on the magnetic properties were studied by dc susceptibility and hysteresis magnetization measurements. The magnetic results revealed a significant enlargement of hysteresis magnetization in tin-added samples with an onset transition temperature drop of only 1–4 K. According to recent measurements, the intragrain Jc reflects the transport critical current density in high field region. The critical current density in Tl,Pb-1223 was enhanced by as much as ten-times by tin-addition. An electron micro-probe technique was employed to locate the added tin in the samples, but Sn incorporated into the superconducting phase was below detectability. The variation in Tc with Sn addition and a reduction in pinning strength at Sn concentration above x=0.05 show that the enhanced pinning is due to introduction of pinning centers into the superconducting phase even though micro-probe analysis indicates that most of the Sn is present in a nonsuperconducting phase. The field dependence and time dependence of the magnetization data showed an increased concentration of pinning centers without a change in pinning energy.

Silsbee rule in YBa2Cu3O7 ceramic superconductors

1989 ◽  
Vol 67 (6) ◽  
pp. 614-616 ◽  
Author(s):  
E. G. Zwartz ◽  
B. A. Judd ◽  
E. Batalla ◽  
L. S. Wright ◽  
W. D. MacDonald
Keyword(s):  
Magnetic Fields ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Ac Susceptibility ◽  
Meissner Effect ◽  
Transport Critical Current Density ◽  
Ceramic Superconductors ◽  
Ceramic Samples ◽  
Alternating Magnetic Fields

The transport critical current density, Jc, and the ac susceptibility have been measured for 28 YBa2Cu3O7, ceramic samples. It is observed that a Silsbee-like rule relates Jc to the alternating magnetic fields at which the ceramics begin to show a reduced Meissner effect.

Dependence of Critical Current Density on Granular Arrangement in Ceramic Superconductors

1992 ◽  
Vol 275 ◽  
Author(s):  
Jui H. Wang ◽  
Zhifeng Ren
Keyword(s):  
Electron Transport ◽  
Critical Current Density ◽  
Single Crystal ◽  
Single Crystals ◽  
Critical Current ◽  
Current Density ◽  
Average Rate ◽  
Weak Links ◽  
Ceramic Superconductors ◽  
Special Cases

ABSTRACTThe critical current density Jc of bulk ceramic superconductors is often several orders of magnitude lower than that of a single crystal or oriented fílm of the same material due to the weak links residing at the boundaries between single crystals within the ceramic sample. Assuming that the rate of electron transport within each single crystal is much faster than the average rate of electron transport between adjacent single crystals, a working hypothesis of Jc enhancement by granular reorientation is formulated which includes the“brickwall”model and melt-texturing as special cases with long-range granular alignment which usually leads to rigid and brittle bulk samples. Simple geometric considerations show that only short-range local granular alignment is necessary for high Jc. For mis reason, it should be possible to make flexible superconducting wires and tapes for commercial applications at or above 77K.

scholarly journals Improvement of Critical Current Density in Bi-2223 Superconductor by Ag-Doping

2019 ◽  
Vol 35 (4) ◽  
Author(s):  
Nguyen Khac Man ◽  
Nguyen Duc Hoa ◽  
Duong Thi Thanh Nhan
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Ac Susceptibility ◽  
Volume Ratio ◽  
Solid State Reaction Method ◽  
Undoped Sample ◽  
Temperature Dependent ◽  
High Tc ◽  
Ag Doping

High-Tc superconducting polycrystalline Bi-2223 undoped sample (A0) and 5wt.% Ag-doped sample (A5) have been prepared by solid-state reaction method at 8550C with sintering time of 8 days. X-ray powder diffraction (XRD) results shown that the major phase of these samples is Bi-2223. The volume ratio of Bi-2223 phase observed to be increased from 78% for undoped sample (A0) to 95% for 5wt.% Ag-doped sample (A5). The enhancement of the onset of high-Tc superconductivity (Tc,onset = 112.5 K) in silver doping sample was observed by DC-resistivity measurements. From the AC-susceptibility measurements combined with Bean critical state model, the temperature dependent parabolic law of inter-granular or matrix critical current density (Jcm) was fitted. Some Jcm values were estimated from these parabolic laws. The results showed that 5wt% Ag-doping can make the Bi-2223 sample with nearly double critical current density.

scholarly journals Effect of geometry and interfacial resistance on current distribution and energy dissipation at metal/superconductor junctions

1989 ◽  
Vol 4 (3) ◽  
pp. 530-538 ◽  
Author(s):  
Meilin Liu ◽  
Lutgard C. De Jonghe
Keyword(s):  
Energy Dissipation ◽  
Critical Current Density ◽  
Contact Resistance ◽  
Critical Current ◽  
Current Distribution ◽  
Current Density ◽  
Power Dissipation ◽  
Superconducting Phase ◽  
Total Power ◽  
Interfacial Resistance

Potential and current distributions and local energy dissipation due to Joule heating in metal-superconductor junctions have been computed as a function of geometric parameters and interfacial resistance. The primary current distribution and power dissipation are highly nonuniform in the system. The secondary current distribution and power dissipation, however, become more uniform as the interfacial resistance increases. Analysis indicates that zero contact resistance is not a stable situation since the primary distribution leads to local current densities exceeding the critical current density of the superconducting phase near the corner of the junction. Local contact failure might then initiate. A finite contact resistance is necessary for a practical application, and the minimum value of the contact resistance can be estimated from the operating current density (javg) of the device and the critical current density (jcri) of the superconducting phase. To obtain an optimum value of the contact resistance, however, one further has to take into consideration the stability and reliability of the device performance, which is, in turn, directly related to the uniformity of the current distribution and power dissipation, to temperature fluctuation of the superconducting phases brought about by local power dissipation, and to the thermal management of the system. Furthermore, a nonuniform contact resistance layer of appropriate profile can redistribute the current more effectively and more uniformly and hence reduce the total power dissipation in the system for a given jmax/javg ratio obtained by a uniform resistance layer.

EFFECT OF THE SECOND PHASE ON CRITICAL CURRENT DENSITY IN Nb-ADDED YBCO FILMS

1995 ◽  
Vol 09 (07) ◽  
pp. 439-443 ◽  
Author(s):  
JUN-HUI JIA ◽  
ZHEN-ZHONG QI
Keyword(s):  
Thin Films ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Superconducting Films ◽  
Superconducting Phase ◽  
Second Phase ◽  
Dc Magnetron Sputtering ◽  
Ybco Films ◽  
Crystalline Substrate

Thin films of YBCO with or without Nb added were prepared on (100) ZrO 2 single crystalline substrate by dc magnetron sputtering method. A phase of YBa 2 NbO 6 was found to form not only in the target materials of YBCO but also in the sputtered thin films. The second phase of YBa 2 NbO 6 in the superconducting films destroyed a match relation between the lattice of YBCO and the lattice of ZrO 2 substrate. The measurements of critical current density J c under magnetic field (H // c axis, up to 5T) showed that the J c in Nb-added YBCO films reduced more apparently than that in YBCO films. It is concluded that the existence of second phase of YBa 2 NbO 6 in superconducting phase does not play a rule of flux pinning.

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