1. Active Electromechanical Nanostructures Without the Use of Piezoelectric Constituents (NSF NIRT Grant )
Pradeep Sharma, University of Houston
Boris Yakobson, Rice University
Ramanan Krishnamoorti. University of Houston
Zoubeida Ounaies, Texas A&M University
Theoretical results: Effect of flexoelectricity on indentation
Flexoelectricity
Apparently Piezoelectric Superlattices without Piezoelectric Constituents
We derived analytical solution of the indentation problem incorporating anisotropy, piezoelectricity and flexoelectricity.
Layered Super-Lattices
Indentation experiments
In parallel, we conducted experiments with varying indentation size…..single crystal BaTiO3
Berkovich indent on BTO surface Load: 8mN; Depth into surface: 200nm
Polarization in each layer of a SrTiO3-MgO-BaTiO3 Periodic Trilaminate (as shown in the inset). Overall average polarization in the Trilaminate is 11% of the Quartz.
NaCl will exhibit an apparent piezoelectric effect when subjected to strain gradients
Contact stiffness vs contact radius for BaTiO3
Indentation size effect?
Indentation experiments indicate a large size effect (see the star-data points). For example, compared to the size-independent behavior (red line), around 10 nm, there is a doubling of contact stiffness.
The curvature of CNT results in rehybridization of p-orbital. As a result, the center of electronic charge at each atomic site is displaced outwards from the nuclear charge.
In principle, the flexoelectric size-effect should be observable in indentation experiments.