Enhancement of piezoelectricity in a mixed ferroelectric

TL;DR

This study uses first-principles calculations to demonstrate that cation ordering and local relaxation significantly enhance the piezoelectric response in Pb_3GeTe_4, with the tetragonal phase showing a threefold increase over the cubic phase.

Contribution

It provides a detailed computational analysis revealing how cation ordering and local relaxation improve piezoelectric properties in a mixed ferroelectric material.

Findings

Tetragonal configuration's piezoelectric coefficient is three times larger than cubic.

Cation ordering and local relaxation weaken ferroelectric instability.

Enhanced piezoelectricity linked to larger cation-anion displacements and higher Born charges.

Abstract

We use first-principles density-functional total energy and polarization calculations to calculate the piezoelectric tensor at zero temperature for both cubic and simple tetragonal ordered supercells of Pb_3GeTe_4. The largest piezoelectric coefficient for the tetragonal configuration is enhanced by a factor of about three with respect to that of the cubic configuration. This can be attributed to both the larger strain-induced motion of cations relative to anions and higher Born effective charges in the tetragonal case. A normal mode decomposition shows that both cation ordering and local relaxation weaken the ferroelectric instability, enhancing piezoelectricity.