Observation of large, untwinned orthorhombic domains in YBa2Cu3O7 single crystals

Abstract
The twinning pattern in single crystals of YBa2Cu3O7 has been studied by differential interference contrast microscopy and transmission electron microscopy. In 10% of crystals studied large untwinned orthorhombic [(ba)/a=2.7%] domains exceeding 100×100 μm2 in area are observed. The structure of twin defects is described and the existence of two types of minority domains is inferred. We infer from the domain structures a mechanism for the growth of twinning patterns in single crystals.