INFLUENCE OF THERMAL CYCLING ON THE LEVITATION FORCE OF MELT-TEXTUREDYBACUO

The influence of thermal cycling on the levitation force of VGF melt-t extured YBaCuO is investigated. With an increasing number of thermal c ycles from room temperature down to the boiling point of liquid nitrog en the levitation force is decreasing. This decrease could be explaine d by the generation and propagation of cracks inside the melt-textured domains which decrease the radii of the screening currents. Furthermo re, water condensed at the surface of the superconductor leads to a de composition of the superconducting Y1Ba2Cu3O7-delta phase and the form ation of large nonsuperconducting areas. (C) 1996 American Institute o f Physics.