Structural modification of twin boundaries in YBa2Cu3O6+η oxides:: Effects of oxygen concentration and temperature

The modification of the twin boundaries in YBa2Cu3O6+eta due to the oxygen ordering below the temperature of the tetragonal-orthorhombic phase transformation has been studied using mean field theory and spatial gradient terms for the oxygen concentration variation. The distribution of the oxygen atoms across the twin boundaries was calculated at various temperatures and oxygen concentration. Based on these calculations, we deduced the interfacial energy, the equilibrium thickness, and the associated oxygen ordering of the twin boundaries. Their effects on twinning and tweed morphology are also discussed.