The microstructure of the twin to tweed transition in aluminium substituted YBa 2Cu 3O 7-∂ single crystals

Abstract

Single Crystals of the superconductor YBa 2Cu 3O 7-∂ have been grown with controlled amounts of aluminium doping just below the twin to tweed transition (1 and 1.5 cationic%) and are examined using single crystal x-ray diffraction and TEM. The nature of the twinning changes from well defined twins and colonies in undoped crystals to an interpenetrating twin morphology as the tweed transition is approached.