ferroelastic

Ferroelastic is a term used to describe a ferroic property in which a material exhibits spontaneous strain that lowers its crystal symmetry and leads to multiple energetically equivalent strain variants. Below a certain transition, the crystal can adopt one of several variants, each with a distinct shape distortion, and the variants are separated by ferroelastic domain walls. The macroscopic shape of the material can be reoriented by applying mechanical stress, resulting in a reversible change of the domain pattern.

Mechanism and properties: The order parameter in a ferroelastic material is the spontaneous strain. Domain switching occurs by the motion of domain walls under applied stress, reconfiguring which variant is present in a region. Depending on the crystal symmetry, switching may involve 90° or 180° reorientation of the distortion. The process often shows hysteresis and is strongly influenced by temperature, loading path, and defects. Ferroelasticity commonly arises from martensitic or other displacive distortions during a structural transition, with a high-symmetry phase at elevated temperature.

Examples: Notable ferroelastic systems include shape memory alloys such as NiTi, where martensitic variants can be stress-reoriented. Some oxide ceramics and perovskites exhibit ferroelastic domain structures, and stabilized zirconia-based ceramics can show ferroelastic switching between tetragonal and monoclinic variants under appropriate conditions.

Applications: The ability to induce large strains with modest stress makes ferroelasticity relevant for actuators and sensors, particularly in smart material systems. Domain engineering in ferroelastic materials also informs elastocaloric cooling concepts and the design of mechanical memory and energy-dissipation control in multifunctional composites. ferroelasticity is a distinct but related concept to ferroelectric and ferromagnetic order, sharing the broader idea of switchable, symmetry-breaking domains.