Formation of tetragonal YBa₂Cu₃O_7−δ from an undercooled melt

Abstract

Containerless processing of YBa₂Cu₃O_7−δ was performed using an aero-acoustic levitation technique. Upon solidification from the liquid, spheres of size 2.5 mm diameter undercooled and recalesced, forming tetragonal YBa₂Cu₃O_7−δ directly from the melt. Subsequent to solidification processing, these samples were annealed to single phase YBa₂Cu₃O_7−δ with orthorhombic symmetry as indicated by powder XRD, SQUID magnetometer measurements indicate a sharp superconducting transition at approximately 85 K. Magnetic J_c values, calculated using the Bean critical state model, indicate that the spheres can carry critical current densities on the order of 10⁴ A cm⁻². Microstructural characterization has been performed on both the as-solidified and annealed spheres.