Local structure and piezoelectric instability in lead-free (1 - X)BaTiO₃-xA(Cu_1/3Nb_2/3)O₃ (A = Sr, Ca, Ba) solid solutions

This study provides a fundamental understanding of the enhanced piezoelectric instability in ABO₃ perovskite based lead-free piezoelectric materials. For this we synthesized (1 - x)BaTiO ₃-xA(Cu_1/3Nb_2/3)O₃ (A: Sr, Ba and Ca and x = 0.0-0.03) solid solutions exhibiting high piezoelectric response. The piezoelectric instability in these compositions was found to increase with x despite monotonous decrease in the long range polar ordering. High energy X-ray diffraction coupled with atomic pair distribution functions (PDF)s indicated an increase in local polarization. Raman scattering and EPR analysis revealed that substitutions on A and B sites both substantially perturbed the local octahedral dynamics and resulted in localized nano polar regions which imparted the high piezoelectric response.