FORMATION OF TETRAGONAL YBA2CU3O7-DELTA FROM AN UNDERCOOLED MELT

Containerless processing of YBa(2)Cu(3)0(7-delta) was performed using an aero-acoustic levitation technique. Upon solidification from the li quid, spheres of size 2.5 mm diameter undercooled and recalesced, form ing tetragonal YBa(2)CU(3)0(7-delta) directly from the melt. Subsequen t to solidification processing, these samples were annealed to single phase YBa(2)CU(3)0(7-delta) with orthorhombic symmetry as indicated by powder XRD. SQUID magnetometer measurements indicate a sharp supercon ducting transition at approximately 85 K. Magnetic J(c) values, calcul ated using the Bean critical state model, indicate that the spheres ca n carry critical current densities on the order of 10(4) A cm(-2). Mic rostructural characterization has been performed on both the as-solidi fied and annealed spheres.