Microstructure and Magnetic Characterization of YBa sub 2 Cu sub 3 O sub 7--x Superconducting Ceramic

Microstructure and microchemistry characterizations of YBCO have been made using analytical transmission electron microscopy to correlate extended defect formation to intergranular and intragranular current density values. AC magnetization curves as a function of applied magnetic field at 4.2 and 77K have been obtained. The results show that a large density of twins favours a high intragranular critical current density. In addition, the formation of cationic non-stoichiometric phases can act as vortex pinning centres. The relatively high intergranular current density is in good agreement with the observed absence of intergranular grain boundary phases.