RECOVERY OF HIGH-TC SUPERCONDUCTIVITY IN Y-BA-CU-O DOPED WITH REACTING METALS

The chemical reactions of YBa2Cu3O7-δ with intimately mixed platinum-group metals (Pt, Pd, Rh, Ru) or Re during sintering severely suppress and broaden the superconducting transition to below ∼ 40 K. However, it has been discovered that an essentially complete recovery of 90 K Tc can be obtained in some samples (doped with Pt, Rh, Re) by proper melt processing of the superconductor. SEM and X-ray analysis indicates that a phase separation occurs during melting of these doped materials, with one of the phases actually draining the doped elements away from the YBa2Cu3O7-δ phase, making the latter essentially chemically pure. The results are of technological interest in view of the lack of high melting-point metals which are non-poisonous in contact with Y-Ba-Cu-O. Some of the metals could be used as a substrate or clad material during high temperature melt processing. © 1990.