Philosophical magazine · 1976 · 51 citations · 10 references
Natural SciencesMaterials SciencePhysicsCondensed Matter PhysicsCrystal StructureSolid State PhysicsDefect CharacterizationDefectsDislocation MechanicsDislocation Burgers VectorsDislocation CharacterizationDislocation Loop FormationDislocation LoopsDislocation PhysicsDislocationsPartial DislocationsTransmission Electron Microscopy Of Dislocations
Abstract Experimental evidence of the existence of 〈010〉 dislocations in the {2 0} prism planes in sapphire has been obtained by transmission electron microscopy. By the weak-beam technique it has been shown that the 〈010〉 dislocations may dissociate into three partials. The partials all have a Burgers vector of ⅓ 〈010〉 and are separated by two identical faults. The distance between two partials is in the range 75-135 Å, corresponding to a fault energy of 320±60 mJ/m2. Perfect 〈010〉 dislocations have also been observed. These dislocations exhibited either one or two peaks when imaged in the (030) reflection by the weak-beam technique. The interpretation of the electron micrographs has been supported by computer simulation of the dislocation images. A faulted dipole has been observed, indicating that some of the prismatic loops often seen to lie in rows along [0001] are faulted with a ⅓ 〈010〉 Burgers vector. A mechanism for the dipole formation is suggested.
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