1993 年 28 巻 4 号 p. 183-190
Recently, high Tc superconducting Y-Ba-Cu-O with relatively high critical current density Jc can be produced by means of various types of melt processes. Applications of the superconductors to bulk magnets, high field shielding, magnetic levitation and so on, are proposed, since the high Jc of the superconducting bulk results in capturing of dense magnetic flux and repelling of high magnetic field. In the present review, it is first pointed out that feasible bulk current density in the superconductors are restricted not only by weak couplings between sub-structures but also by electro-magnetic properties such as flux creep and flux jump. The processing of bulk Y-Ba-Cu-O is outlined at viewpoint of improvement of Jc, while the limited level of the current density due to the undesirable phenomena is presented. Experimental and theoretical works for the prospective applications of high Tc bulk superconductors are summarized.