TY - JOUR
T1 - Critical temperature in bulk ultrafine-grained superconductors of Nb, V, and Ta processed by high-pressure torsion
AU - Nishizaki, Terukazu
AU - Edalati, Kaveh
AU - Lee, Seungwon
AU - Horita, Zenji
AU - Akune, Tadahiro
AU - Nojima, Tsutomu
AU - Iguchi, Satoshi
AU - Sasaki, Takahiko
N1 - Funding Information:
The authors are grateful to Professors M. Kato and T. Ishida of Osaka Prefecture University and Professor M. Mito of Kyushu Institute of Technology for fruitful discussions. The author (T.N.) is also grateful to Mr. S. Terada and Mr. Y. Matsuzaki of Kyushu Sangyo University for their assistance with resistivity measurements. This work was supported by JSPS KAKENHI (Grant Number 16K05460). The magnetization measurements were partly performed at the Advanced Instruments Center at Kyushu Sangyo University. The HPT process was carried out in the International Research Center on Giant Straining for Advanced Materials (IRC-GSAM) at Kyushu University.
Publisher Copyright:
© 2019 The Japan Institute of Metals and Materials.
PY - 2019/1/1
Y1 - 2019/1/1
N2 - 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 Tc in Nb increases with the evolution of grain refinement owing to the quantum confinement of electrons in ultrafine grains. In V and Ta, however, Tc decreases at a certain HPT revolution number (i.e. at certain strain levels). The different behaviour of Tc 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.
AB - 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 Tc in Nb increases with the evolution of grain refinement owing to the quantum confinement of electrons in ultrafine grains. In V and Ta, however, Tc decreases at a certain HPT revolution number (i.e. at certain strain levels). The different behaviour of Tc 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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U2 - 10.2320/matertrans.MF201940
DO - 10.2320/matertrans.MF201940
M3 - Review article
AN - SCOPUS:85068899058
SN - 1345-9678
VL - 60
SP - 1367
EP - 1376
JO - Materials Transactions
JF - Materials Transactions
IS - 7
ER -