Origins of large enhancement in electromechanical coupling for nonpolar directions in ferroelectric BaTiO3

TL;DR

This study investigates the lattice dynamics behind the large electromechanical coupling in nonpolar directions of BaTiO3, revealing how phonon interactions enhance piezoelectric properties and guiding the design of better materials.

Contribution

It uncovers a lattice dynamics mechanism involving phonon interactions that explains enhanced piezoelectric coupling in nonpolar directions of BaTiO3.

Findings

Electric field causes phonon spectrum changes near the Brillouin zone center.

Enhanced interaction between transverse acoustic and optic phonons.

Provides a mechanism for improved piezoelectric material design.

Abstract

The origins of enhanced piezoelectric coupling along nonpolar crystallographic directions in ferroelectric BaTiO3 are investigated using in situ neutron spectroscopy. It is observed that an electric field applied away from the equilibrium polarization direction causes changes in the phonon spectra that lead to an increase in the interaction between the transverse acoustic and transverse optic branches (TA-TO) near the Brillouin zone center. This provides a direct lattice dynamics mechanism for enhanced electromechanical coupling, and could act as a guide for designing improved piezoelectric materials.