| Project/Area Number |
09650355
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Electronic materials/Electric materials
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| Research Institution | Nagoya University |
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Principal Investigator |
INOUE Masumi Nagoya University, Department of Quantum Engineering, Assistant Professor, 工学研究科, 講師 (00203258)
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| Project Period (FY) |
1997 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 1998: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 1997: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Keywords | oxide superconductor / BSCCO / thin film / critical current density / annealing / surface resistance / intrinsic junction |
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| Research Abstract |
The critical current density J_C required for Bi_2Sr_2Ca_<n-1>Cu_n0_x(BSCCO) superconductors depends on the application. Therefore, the control of J_C over a wide range is necessary for the practical application of this material. In this research, the control of J_C of BSCCO high-quality films by annealing and the relationship between J_C, and other material properties were investigated using the 2212 phase (n=2).
1. Control of the Critical Current Density by Annealing :
Since J_C does not reflect the intrinsic material properties when the film is composed of small grains, annealing in oxygen at high temperatures was tried and grains as large as the mesa size could be obtained. By controlling the oxygen content in BSCCO by annealing in nitrogen at low temperatures, J_C along the c-axis direction decreased over the range of 10^4-10^1A/cm^2 with increasing annealing time. The critical temperature increased steeply and then decreased slowly as a function of the annealing time. It was suggested that these phenomena reflect the change in the carrier density.
2. Relationship between the Critical Current Density and Other Properties :
Relationship between J_C along the ab-direction and the surface resistance was mainly investigated. The dependence of the surface resistance on the product of the grain size and J_C, which is reported for Y-system superconductors, was not confirmed, while its dependence on J_C, was suggested.
3. Application Possibility of the Control Method of the Critical Current Density :
As an application of the control method of J_C, intrinsic junctions were fabricated and the correlation between J_C and the device properties was investigated. Their current-voltage (I-V) characteristics were classified into two types : one was the flux-flow type and the other was the multiple-branching type typical for intrinsic junctions showing voltage jumps and hystereses. The I-V curve with multiple branches was observed for samples with J_C of 10^3A/cm^2 or less.
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