Influence of elaboration on the microstructure and on the electrical and magnetical properties in YBaCuO ceramics

The microstructure of the high Tc superconductors is known to have a great effect on the electrical and magnetical properties. In order to correlate the elaboration conditions with the microstructure and physical properties, different YBaCuO ceramic superconductors have been prepared using various treatment conditions. The microstructure has been characterized by optical, scanning and transmission electron microscopy techniques (SEM, TEM, STEM). Chemical analyses have also been performed. The ceramics present various grain sizes. The 123 phase is sometimes associated with the 211 or with a phase presenting a barium deficiency and a copper excess. Different kinds of extended defects such as intergranular phases, stacking faults and dislocations have been observed. Room temperature resistivity, Tc, transition width, Hc 2 w, transport critical current density and magnetic shielding have been measured. Microstructures and superconducting properties appear to be strongly linked.