銀シース酸化物高温超伝導テープ材の臨界電流密度

抄録

In the technological point fo view, the powder-in-tube method is very useful for preparing the superconducting composite. In order to achieve high critical current density (Jc), the thermomechanical treatment by which heat treatment and cold working are repeated several times, has been known to be effective. Here, the changes of Jc by different TMT techniques for Ag sheathed YBaCuO and BiPbSrCaCuO superconducting tapes have been mentioned and the metallurgical factors improving Jc were discussed. The Jc of YBCO tapes increased with decreasing oxide layer thickness. The specimen with 3, 300A/cm² at 77K consisted of the preferred oriented grain structure of 123 phase with low prosity. The Jc was greatly improved by SnO₂ addition. In the BPSCCO tapes, the optimum chemical composition was estimated. The annealing was performed in the temeprature region between 1113 and 1118K. The major superconducting phase 2223 phase was accompanied by minority 2212 and 2201 phases and several impurity phases of CuO, Ca₂PbO₄ and (Sr, Ca)₃Cu₅O_x. The specimen with 19, 000A/cm² at 77K consited of highly laminated grain structure. As BPSCCO tapes exhibited enough Jc for instance, exceed 5×10⁴A/cm² at 10T at 4.2K, the mechanical property is suggested to be the next research subject for practical applications.