TRANSMISSION ELECTRON MICROSCOPY OBSERVATION OF THE DECOMPOSITION OF YBa2Cu4O8 INTO YBa2Cu3O7-DELTA AND CuO

The decomposition of YBa2Cu4O8 (Y-124) into YBa2Cu3O7-delta (Y-123) and CuO at high temperatures was expected to create Y-123 with finely dispersed CuO precipitates suitable for flux pinning. Samples of thermally decomposed Y-124 exhibited a critical current density, Jc, which is enhanced with respect to the starting material and to pure Y-123. TEM studies of furnace annealed Y-124 were not suitable to clarify the reason for this Jc enhancement. The formation and growth of CuO precipitates was observed by in situ decomposition of the Y-124 starting material due to electron beam heating within the TEM. 27 refs.