STABILITY AND EVOLUTION OF STACKING-FAULTS IN MELT-TEXTURED YBA2CU3O7-X

The annihilation process of large 1/6 < 301 > stacking faults in melt textured YBa2Cu3O7-x is in situ monitored in the transmission electron microscope. The process is activated at the onset of the orthorhombic to tetragonal transition induced in the electron microscope, thus evi dencing the instability of such defects in the deoxygenated YBa2Cu3O7- x matrix. The observations suggest that the annihilation (and growth) process is limited by surface diffusion along Y2BaCuO5/YBa2Cu3O7-x int erfaces. The propagation mechanism of such stacking faults is addresse d in the light of the present findings. (C) 1997 American Institute of Physics.