Orientational Contribution to the Giant Electrostriction Effect and   Dielectric Permittivity in Relaxors
  A microscopic model is developed considering randomly oriented polar regions stuck to the directions of random fields or stresses. The application of an external field (stress) in this model results in a dielectric and acoustic reply connected with a polarization (strain) rotation. Polarization (strain) fluctuation contributions are also studied. 
S. A. Prosandeev