1987 Fiscal Year Final Research Report Summary
Experimental Models on Grain Boundary of Metastable Superconductors.
| Project/Area Number |
61550017
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Applied materials
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| Research Institution | Kagoshima University |
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Principal Investigator |
KOZO Obara Faculty of Engineering, Kagoshima University, 工学部, 助手 (10094129)
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| Co-Investigator(Kenkyū-buntansha) |
TOSHIKAZU Hirose College of Liberal Arts, Kagoshima University, 教養部, 教授 (50041778)
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| Project Period (FY) |
1986 – 1987
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| Keywords | Superconductor / Metastable material / Oxide / Super-fine particles / ジョゼフソン効果 |
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| Research Abstract |
Electrical characteristics of experimental grain boundary models which have the energy dissipation in the superconductive state were investigated. Three types were used as models: two dimensional S-N-S junction array, agglomeration of super-fine particles of niobium oxides and agglomeration of La-Sr-Cu-O superconductors.
1) Two dimensional S-N-S junction array
Resistance increases of an activation type were found below Tc of grains. These characteristics strongly depended on the inhomgeneous granular structure of the grain boundary. Periodic stair-like resistance drops were found in the R-T dependence.
2) Agglomeration of super-fine particles of niobium oxides
Metastable super-fine particles which have an average diameter 250 A were obtained by the sputtering under 0.3 torr argon. An analitical model to investigate the oxidation mechanisum from the time dependence of electrical resistance was proposed. The relation between growth rates of the oxide and oxygen pressures showed the existence of fine metastable structures.
3) La-Sr-Cu-O superconductor
The resistance of grain boundary showed a semiconductive temperature
dependence. Two resistance anomalies which strongly depended on current were found. One peak existed in the transition region of bulk superconductor and weakly deacreased its transition temperature as current increased. The transition temperature of another peak strongly depended on current and it was observed up to 300K. The region of two peaks consisted of discrete voltages which formed a geometrical series. This shows that electronic systems in the sample are strongly correlated each other and are expressed by only three macroscopic wave functions.
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Research Products
(18 results)
