Dislocations in MgB 2

The types of dislocation most commonly occurring in the superconductor MgB 2 are investigated. Dislocations belonging to both the basal and the non-basal types have been observed. At 2 nm spatial resolution, dissociation of the basal dislocations into Shockley partials is not observed. The dislocation shapes are irregular, but many segments of dislocation are fairly straight. The core structure of the non-basal dislocations, with b = [0001] has also been observed by high-resolution electron microscopy. A step-like structure is suggested for this sessile dislocation.