期刊
MATERIALS TRANSACTIONS
卷 60, 期 7, 页码 1367-1376出版社
JAPAN INST METALS & MATERIALS
DOI: 10.2320/matertrans.MF201940
关键词
high-pressure torsion; superconductivity; bulk ultrafine-grained metals; niobium; vanadium; tantalum; critical temperature; magnetization; resistivity
资金
- JSPS KAKENHI [16K05460]
- Grants-in-Aid for Scientific Research [16K05460] Funding Source: KAKEN
This overview describes the progressive results of the superconducting critical temperature in bulk nanostructured metals (niobium, vanadium and tantalum) processed by high-pressure torsion (HPT). Bulk nanostructured superconductors provide a new route to control superconducting property, because ultrafine-grain structures with a high density of grain boundaries, dislocations, and other crystalline defects modify the superconducting order parameter. The critical temperature T-c in Nb increases with the evolution of grain refinement owing to the quantum confinement of electrons in ultrafine grains. In Vand Ta, however, T-c decreases at a certain HPT revolution number (i.e. at certain strain levels). The different behaviour of T-c in the three materials is explained by the competition effect between the quantum size effect and disorder effect; these effects are characterized by the parameters of grain size, electron mean free path, and superconducting coherence length.
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