ENHANCED CRITICAL CURRENTS BY CEO2 ADDITIONS IN DIRECTIONALLY SOLIDIFIED YBA2CU3O7

The microstructure and critical currents of superconducting YBa2Cu3O7- Y2BaCuO5 composites with small CeO2 additions prepared using a directi onal solidification procedure have been investigated. The small CeO2 a dditions cause the decomposition of the Y2BaCUO5 phase leading to the formation of Y2O3 and BaCeO3. Experimental evidence is given for the s ubsequent nucleation of the Y2BaCuO5 phase on the Y2O3 particles. This new decomposition-nucleation mechanism leads to textured YBa2Cu3O7 ha ving enhanced critical currents. An addition of 0.3 wt % CeO2 can incr ease J(c)ab by a factor of 2 in samples having similar concentration o f Y2BaCUO5 precipitates. Critical currents above 10(5) A/cm2 at 77 K a nd zero field are obtained by this method.