Piezoelectric enhancement under negative pressure

Enhancement of ferroelectric properties, both spontaneous polarization and Curie temperature under negative pressure had been predicted in the past from first principles and recently confirmed experimentally. In contrast, piezoelectric properties are expected to increase by positive pressure, through polarization rotation. Here we investigate the piezoelectric response of the classical PbTiO 3 , Pb(Zr,Ti)O 3 and BaTiO 3 perovskite ferroelectrics under negative pressure from first principles and find significant enhancement. Piezoelectric response is then tested experimentally on free-standing PbTiO 3 and Pb(Zr,Ti)O 3 nanowires under self-sustained negative pressure, confirming the theoretical prediction. Numerical simulations verify that negative pressure in nanowires is the origin of the enhanced electromechanical properties. The results may be useful in the development of highly performing piezoelectrics, including lead-free ones. Recently, negative pressure has been observed in perovskite nanowires by annealing the wires from a lower-density phase. Here, the authors show that the negative pressure enhances the piezoelectric coefficient of PbTiO 3 and Pb(Zr,Ti)O 3 nanowires experimentally and by ab initio calculations.