E1-11
One of the most important parameter for potential applications ofhigh-Tc superconductors is the critical current density (Jc) and itsdependence on the magnetic field. Recently developed oxygen controlledmelt growth (OCMG) process showed that Jc values increased drastically inNd123 system with increasing an applied field up to 1.2T in 77K anddisplayed a peak effect with the field dependence. Later it wasexperimentally confirmed that OCMG process also seems to be effective forother RE systems including Sm and Eu. We have further extended thisprocess to ternary and quaternary RE123 systems, as their melting pointsare lower than RE123 systems. And this may be very promising consideringthe viewpoint of engineering process. It will also be possible to usethese materials to make joints between the two RE123 superconductors. Inthis paper we will decribe the growth and superconducting properties ofternary and quaternary RE123 systems prepared by the OCMG p! rocess. XRD, SEM and EPMA results indicate that grown crystals mainlyconsist of 123 phase with a small amount of second phase. SQUID, VSM andA.C. Susceptibility results on these oxygenated samples showed that Tc(onset) was in the range of 93 to 95.3K. All the samples showed ananomalous peak effect in the magnetization hysteresis (M-H) loops. Thehighest critical current density value obtained in this series of systemswas about 50, 000 A/cm2 at 77K and 2T in case of H//c axis of the sample.(Nd-Sm-Eu-Gd)123 and (Sm-Eu-Gd)123 composites processed at Ar-1% O2 atm.,even for H//C the M-H loops are open till 7T (at 77K) which was upper limitof magnetic field in our experiment. We propose that the irreversibilityfield exceeding 7T at 77K and large Jc at relatively higher fields ispossibly a result of improved field induced flux pinning caused bystructural variations in the presence of three rare earths within 123matrix.