A comparison of [0 0 1] low-angle tilt grain boundaries of (1 0 0) and (1 1 0) grain boundary planes in YBa₂Cu₃O_7-δ coated conductors

The microstructure and grain boundary structure in YBa₂Cu₃O_7-δ (YBCO) thick film coated conductors are characterized by transmission electron microscopy. The films contain low-angle [0 0 1] tilt grain boundaries with periodic arrays of edge dislocations parallel to the c-axis. A majority of the grain boundary planes are of either the (1 0 0) or the (1 1 0) type. Grain boundary dislocations (GBDs) with a [1 0 0] Burgers vector were observed in tilt boundaries with (1 0 0) boundary planes. However, partial dislocations, separated by stacking faults, were found at boundaries with near (1 1 0) grain boundary planes. Extensive g · b and g · R analyses confirmed the partials to be of 1/2[1 1 0] type. These results suggest that the characteristics of dislocation structures, which have been proposed in various grain boundary-based flux-pinning models, depend not only on the misorientation angle θ, but also on the types of grain boundary plane. The effect of dissociated GBDs on the transport properties of low angle grain boundaries in YBCO coated conductors is discussed.