All-Mechanical Polarization Control and Anomalous (Electro)Mechanical Responses in Ferroelectric Nanowires

Abstract

Piezoelectric and ferroelectric nanowires exhibit properties and phases that are not available in the bulk. They are extremely promising for functional nanoscale application. On the basis of atomistic first-principles-based simulations, we predict an all-mechanical polarization control in ferroelectric nanowires. We report that the application of uniaxial compressive stress to ferroelectric nanowires with poor surface charge compensation leads to a reversible phase switching between the polar phase with axial polarization and macroscopically nonpolar flux-closure phase. The phase switching is associated with anomalously large changes in polarization and piezoelectric and mechanical response. In particular, in PbTiO nanowires the values as large as 5400 pC/N and 140 TPa are predicted for the piezoelectric coefficient and elastic constant, respectively. Remarkably, the effect persists up to the gigahertz frequency which is potentially promising for nanoscale applications, such as nanogenerators, biomedical electronics, monitoring devices, nanosensors, nanotransducers, and nanoactuators.

Insight into Pyroelectricity and Phase Transitions in Ferroelectrics from Nonequilibrium Approach: The Case of PbTiO3

“…This Hamiltonian predicts phase transition from paraelectric cubic to ferroelectric tetragonal at 605 K which somewhat underestimates the experimental value of 763 K. [19] It correctly reproduces first-principles soft mode frequency and has been previously used to study dynamics of both PbTiO 3 , bulk and nanostructures. [20][21][22][23] The degrees of freedom for the Hamiltonian included local soft modes which were proportional to the local dipole moments and local strain variables that describe deformation of the unit cells. The Hamiltonian includes the interactions that are responsible for the ferroelectricity in PbTiO 3 : local mode self energy up to fourth order, harmonic short and long range interactions between the local modes, elastic deformations, and interactions responsible for the electrostriction.…”

Enhanced Piezoelectric Response at Nanoscale Vortex Structures in Ferroelectrics

“…Such an approach has previously been used to simulate the dynamical and equilibrium properties of ferroelectrics and their nanostructures. 18,19,21,23 The dc electric field was applied and removed by a sequential increase and decrease, respectively, from 0 to 2000 kV/cm.…”

“…Experiments, ,− as well as many simulations, − have beautifully established the presence of multiple phases and polarization rotations in BTO-based compositions at the nanoscale. Our previous Bragg coherent diffractive imaging (BCDI) work, coupled with phase field simulations, has also identified the monoclinic phase and shown how the phase fractions change as the vortex is driven under the influence of an external field .…”

Mechano‐Nanoarchitectonics: Design and Function

“…As mechanical controls of physical properties, Ponomareva and co‐workers demonstrated all‐mechanical controls of ferroelectric nanowires. [ 43 ] Upon application of uniaxial compressive stress onto ferroelectric nanowires such as PbTiO 3 nanowires, their poor surface charge compensation results in reversible phase switching between macroscopically nonpolar flux‐closure phase and polar phase with axial polarization. The observed mechanical effect is hold up to GHz frequency regions.…”