ABSTRACT
In regard to Maxwel l ' s equations, one of the most significant differences between
granular-type high-Tc and ordinary superconductors is that the former have an
extra level of magnetic structure not possessed by the latter (Figure 11.1). In
ordinary superconductors current can flow freely through crystal grain boundaries
but, as mentioned in the Introduction, in high-Tc materials grain boundaries,
unless the grains are highly oriented, offer an appreciable barrier to current flow.