Kabushiki Kaisha Toshiba

Ken Ando

Noburu Fukushima

Hiromi Niu

Hisashi Yoshino

Shunji Nomura

Tomohisa Yamashita

A substance which has a Cu--O plane containing crystal structure in its unit cell and which is called a Bi oxide superconductor consisting essentially of Bi, Sr, Ca, Cu, and O. Not only part of Bi but also part of Sr and/or Ca of the Bi oxide superconductor is substituted for Pb and rare earth elements (RE), respectively. The Pb substitution relaxes the structural modulation which is closely related to superconductivity of the Bi oxide superconductor and the RE substitution controls its carrier concentration. Accordingly, superconducting properties such as transition temperature and critical current density can be improved remarkably. In addition, not only oxide superconductors with excellent superconductivity can be prepared in a low oxygen content but also the surface condition of the prepared superconductors is stable.

Bi oxide superconductors

An insulating composition consisting of Bi, Sr, RE, Cu, O or of Tl, Ba, RE, Cu, O (wherein; RE is an element selected from a group consisting of Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) aligns properly with a crystal face of an oxide superconductor because its crystal structure is the same as or similar to that of the oxide superconductor. An insulating composition in which a part of Bi is replaced by Pb is further near the oxide superconductor its construction, and the modulation structure in this insulating composition is mitigated or disappears.

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Yokohama, Japan

Ken Ando