THE EFFECT OF HEAT-TREATMENT ON EXPLOSIVELY COMPACTED (Y-BA-K-CU-O) SUPERCONDUCTIVE POWDERS

A ceramic powder mixture corresponding to the stoichiometric ratio of YBa1.95K0.05Cu3Oy superconducting ceramic with 10% w/w Ag was heat tre ated at 950 degrees C for 3 h in flowing oxygen. The resultant superco nducting powder was consolidated in a silver tube by the explosive com paction technique (pre-heat treated ceramic). The same fabrication tec hnique, i.e. explosive compaction, was employed to the initial stoichi ometric powder mixture, without prior heat treatment and the green pro duct was subsequently subjected to a series of heat-treating cycles (9 20 degrees C, 70 h), in order to obtain the required superconducting p roperties (post-heat treated ceramic). The microstructure and physical properties of the pre-and post-heat treated ceramics were analyzed an d compared using various characterization techniques. X-ray diffractio n performed on the pre-heat and post-heat treated ceramics indicated t hat maximum 123-phase content retained in the former case (pre-heat tr eated ceramic), whilst DC magnetic susceptibility measurements have sh own the characteristic Meissner shielding effect at 99 and 92 K, respe ctively. Furthermore, the pre-heat treated compacted billet was charac terized by a critical current density, J(c) equal to 2800 A/cm(2) at 7 7 K after suitable annealing at 850 degrees C for 10 h in oxygen strea m. (C) 1997 Elsevier Science B.V.