Incipient Twinning in Ba2YCu3O7-x Crystals

Abstract

Twinning in Ba₂YCu₃O_7-x crystals prepared by the standard sintering method was examined by electron optical methods. Under electron beam irradiation in a vacuum in an electron microscope, an orthorhombic crystal transformed irreversibly to a tetragonal form. Prior to the complete transformation, an “incipient” twinning state was observed. The incipient state is considered in terms of domain formation of a tetragonal form.