An examination was made of the interrelationship between the oxygen stoichiometry, mobility and ferro-elastic properties in YBa2Cu3O7-δ. Changes in the oxygen stoichiometry, δ, affected the orthorhombic-tetragonal phase transformation and thus could be expected to affect directly the ferro-elastic domain structure. A free-energy formulation was used to derive an expression for the energy of a {110} twin wall in terms of the spontaneous strain, coercive stress and twin wall separation. An upper limit of 40mJ/m2 was estimated. The ferro-elastic viscosity was assumed to be an activated process which depended upon both the diffusivity and concentration of oxygen. Two types of domain reorientation were proposed: a cooperative shear process of oxygen along a twin wall, and a stress-assisted short-range oxygen hopping process in the bulk of the domain. Both were expected to be strongly dependent upon the oxygen content and mobility.

Oxygen Stoichiometry and Mobility Effects on Domain Wall Motion in Ferroelastic YBa2Cu3O7-δ. J.R.LaGraff, D.A.Payne: Ferroelectrics, 1992, 130[1-3], 87-105