Ceramics and Composite Materials

Antiferroelectrics (AFE) can exhibit a ‘shape memory function controllable by electric field’, with huge isotropic volumetric expansion associated with the AFE to Ferroelectric (FE) phase transformation. In the Pb0.99Nb0.02[(Zr0.6Sn0.4)1-yTiy]0.98O3 (PNZST) system, the shape memory function is observed in the intermediate range between high temperature AFE and low temperature FE, or low Ti-concentration AFE and high Ti-concentration FE. In the AFE multilayer actuators (MLA’s), the crack is initiated in the center of a pair of internal electrodes under cyclic electric field, rather than the edge area of the internal electrodes in normal piezoelectric MLA’s. The two-sublattice polarization coupling model is proposed to explain: (1) isotropic volume expansion during the AFE-FE transformation, and (2) piezoelectric anisotropy. We introduce latching relays and mechanical clampers as possible unique applications of shape memory ceramics.