The experimental evidence on the existence of fourfold ferroelastic domain wall

In order to verify the existence of fourfold ferroelastic domain wall, which is suggested by group-theoretical consideration, polarizing microscopy and X-ray Laue photography experiments were carried out for BiVO₄ crystal which is expected to have fourfold walls only. The experimental results showed that the domains in ferroelastic BiVO₄ have fourfold rotational symmetry relationship and the domain walls are characterized by these fourfold symmetry elements. This proves the domain walls in BiVO₄ to be the fourfold wall and they were indexed as (101) and (101) in monoclinic reference system.