Shape-memory effect in PMN-PT(65/35) ceramic

We report the observation of fairly large and fully recoverable shape-memory strain in thin bars of lead magnesium niobate lead titanate ceramic for a composition (65/35) near its morphotropic phase-boundary. The recoverable shape strain produced by bending and thermal-cycling experiments is ∼0.3%, similar in magnitude to that reported for the shape-memory effect (SME) observed in some other dielectric ceramics. An explanation of the observed SME and the recoverable shape-strain is given in terms of the ferroelastic phase transitions, and the availability of a large number of competing phases and domain states near the morphotropic phase boundary in this material. The stress-induced shifting of the temperatures at which the ferroelastic phase transitions occur also plays an important role in ensuring good crystallographic reversibility around the thermal-cycling experiments.