Apparent Young's modulus in PMN-PT electrostrictive ceramics

Some electrostrictive ceramics like 0.9 PMN-0.1 PT show large reduction of the apparent Young's modulus (more than 50%) as a function of the electric field. In the literature, this result is always obtained in the direction o f the applied electric field. We performed some measurements of the elastic modulus in the direction perpendicular to the electric field and we found an unexpected small variation (less than 6%). This result shows that the ap parent mechanical properties are much more dependent of the direction of th e electrical field than known previously.