Influence of silver addition on cracking in melt-grown YBCO

The influence of silver addition on a-b microcracking and c-cracking in mel t-grown YBa2Cu3O7/Y2BaCuO5 single-grain superconductors of nominal composit ion YBa2Cu3O7 + 0.24Y(2)O(3) + 0.02Pt was studied by optical microscopy. Th e spacing of the a-b microcracks increased from 1.8 to 3.7 mum and the spac ing of the c-cracks increased from 34.2 to 133.5 mum when 12 wt.% Ag was ad ded. This behavior can be associated with microstresses introduced by Ag pa rticles. Higher volume change of the Ag than of the YBa2Cu3O7/Y2BaCuO5 matr ix during cooling down from the processing temperature and during oxygenati on causes compressive tangential stresses around Ag particles and therefore cracking is suppressed. This suppression of cracking by Ag particles leads to slower oxidation of YBa2Cu3O7/Y2BaCuO5 single-grain superconductors. (C ) 2001 Elsevier Science B.V. All rights reserved.