Institution: | a Department of Mechanical Engineering, National Technical University of Athens, 106 82, Athens, Greece b Department of Silicate and Materials Engineering, University of Veszprem, Veszprem, Hungary c Metalltech Ltd., Budapest, Hungary |
Abstract: | A ceramic powder mixture corresponding to the stoichiometric ratio of YBa1.95K0.05Cu3Oy superconducting ceramic with 10% w/w Ag was heat treated at 950°C for 3 h in flowing oxygen. The resultant superconducting powder was consolidated in a silver tube by the explosive compaction technique (pre-heat treated ceramic). The same fabrication technique, i.e. explosive compaction, was employed to the initial stoichiometric powder mixture, without prior heat treatment and the green product was subsequently subjected to a series of heat-treating cycles (920°C, 70 h), in order to obtain the required superconducting properties (post-heat treated ceramic). The microstructure and physical properties of the pre- and post-heat treated ceramics were analyzed and compared using various characterization techniques. X-ray diffraction performed on the pre-heat and post-heat treated ceramics indicated that maximum 123-phase content retained in the former case (pre-heat treated ceramic), whilst DC magnetic susceptibility measurements have shown the characteristic Meissner shielding effect at 99 and 92 K, respectively. Furthermore, the pre-heat treated compacted billet was characterized by a critical current density, Jc equal to 2800 A/cm2 at 77 K after suitable annealing at 850°C for 10 h in oxygen stream. |