Optical study of a phase coexistence in KHCO3

The nature of the phase boundary between ferroelastic domains which coexist with the monoclinic phase of KHCO3 below Tc = 318K is investigated by means of anisotropic refraction of light in the crystal. This interface whose orientation is measured with a precision of ∼ 0.2 degree is shown to correspond to a W'-wall of the ferroelastic domain-wall theory. This allows us to conclude that the observed domains consist of a triclinic phase.

Keywords:

• Ferroelastic
• domain
• domain wall
• phase coexistence