STRUCTURE AND ELECTRICAL-PROPERTIES OF GRAIN-BOUNDARIES ALLOWING LARGE TRANSPORT CURRENTS IN HIGH SUPERCONDUCTING CERAMICS

The relationships between the local electrical behaviour and the structure of grain boundaries, in MTG textured YBaCuO, have been investigated. The microprobe method combined with the technique of microcontacts, deposited by photolithography, leads to very reproducible voltage drop measurements. Longitudinal grain boundaries parallel to the texture exhibit high electrical barriers at room temperature. Cross-grain boundaries display low electrical barriers. The orientation relationships between grains, as well as the geometry of the boundary, greatly influence the electrical behaviour of boundaries. The local data could be conducive to a new texture and particularly to the improvement of the mechanical behaviour of this type of material.