Ferroelastic phase transition in BiVO₄: VI. Some comments on the relationship between spontaneous deformation and domain walls in ferroelastics

For pt.V see ibid., vol.16, p.5127 (1983). The relationship between the domain wall orientation and the spontaneous strain in ferroelastics is discussed, with particular reference to the W' walls in BiVO 4 . The microscopic, wall-defining property is shown to be the coherence of the lattices of the twin components. This concept, commonly used in metallurgy, is valid for both finite and infinitesimal strains and is more fundamental than the macroscopic strain compatibility condition derived by previous workers in the field of ferroelasticity. Observations of domain walls in BiVO 4 as a function of temperature are presented which suggest that they may be of importance in determining the properties of the material close to the ferroelastic phase transition.