高Ｔｃ酸化物超電導線材

Abstract

Present status of R & D on high-Tc oxide superconducting tape and wire conductors is reviewed. For Bi-based oxide, tape and wire conductors are fabricated by powder methods such as Ag sheath method, dip-coating method and jelly-roll method. Grain orientated microstructure is easily obtained by these methods because of strong two-dimensionality of the Bi-based oxide and coupling of grains is much improved. Transport Jc of -105A/cm2 is attained in high magnetic fields over 20T at-4.2K. Recently, small coils are fabricated using Bi-based oxides and promising results are obtained. However, Jc in fields decreases rapidly with increasing temperatures. This is also due to the strong two-dimensionality. Y-123 and Tl-1223 show less strong two-dimensionality and, hence, more excellent flux pinning characteristics at high temperatures. For these oxides, however, it is difficult to obtain grain oriented microstructure by powder methods. This results in weak coupling of grains and small transport Jc. For Y-123 and Tl-1223, excellent transport Jc can be obtained in films. Biaxially grain oriented Y-123 short tapes prepared by laser ablation technique and Tl-1223 thick films prepared by spray coating method show excellent Jc-B characteristics at 77K.