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 of 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 apparent mechanical properties are much more dependent of the direction of the electrical field than known previously.