Ultrahigh measured electrostrain in polycrystalline bulk piezoceramics: Role of mechanically relaxed grains

Recently we found that when conventional bulk polycrystalline piezoceramics discs (~ 10 mm diameter) are thinned down to thickness ~ 200 microns or below, the measured unipolar electrostrain (UES) values increased phenomenally (arXiv:2208.07134). Here we demonstrate that this anomalous phenomenon correlates strongly with the decrease in the degree of mutual mechanical clamping between the grains which in turn enables enhanced switching of the ferroelastic domains.