Characterization of the effective electrostriction coefficients in ferroelectric thin films

Abstract

Electromechanical properties of a number of ferroelectric films including PbZrxTi1−xO3(PZT), 0.9PbMg1/3Nb2/3O3–0.1PbTiO3(PMN-PT), and SrBi2Ta2O9(SBT) are investigated using laser interferometry combined with conventional dielectric measurements. Effective electrostriction coefficients of the films, Qeff, are determined using a linearized electrostriction equation that couples longitudinal piezoelectric coefficient, d33, with the polarization and dielectric constant. It is shown that, in PZT films, electrostriction coefficients slightly increase with applied electric field, reflecting the weak contribution of non-180° domains to piezoelectric properties. In contrast, in PMN-PT and SBT films electrostriction coefficients are field independent, indicating the intrinsic nature of the piezoelectric response. The experimental values of Qeff are significantly smaller than those of corresponding bulk materials due to substrate clamping and possible size effects. Electrostriction coefficients of PZT layers are shown to depend strongly on the composition and preferred orientation of the grains. In particular, Qeff of (100) textured rhombohedral films (x=0.7) is significantly greater than that of (111) layers. Thus large anisotropy of the electrostrictive coefficients is responsible for recently observed large piezoelectric coefficients of (100) textured PZT films. Effective electrostriction coefficients obtained by laser interferometry allow evaluation of the electromechanical properties of ferroelectric films based solely on the dielectric parameters and thus are very useful in the design and fabrication of microsensors and microactuators.

Effect of domain walls on the electrocaloric properties of Pb(Zr1−x,Tix)O3 thin films

“…In reality lattice imperfections or defects can pin domain walls, hinder their movement, and reduce the extrinsic contribution. 20,21 The extrinsic contribution to electrocaloric response will be zero in the case of completely pinned domain walls, and our calculation, in effect, places an upper bound on the extrinsic contribution to the electrocaloric properties. Recent experimental results have demonstrated that while it is challenging to fabricate defect-free ferroelectric films, advances in thin film growth techniques can yield low defect density films, a few hundred nanometers in thickness, that exhibit significant extrinsic contributions to the dielectric response.…”

Investigation of phase transition in ferroelectric Pb0.70Sr0.30TiO3 thin films

“…Well-known examples are lead magnesium niobate ͑PMN͒, lead zinc niobate ͑PZN͒, and their solid solutions with lead titanate ͑PT͒, which are the most widely studied relaxor materials. [8][9][10][11] However, some lead-free compounds were also recently found to present a relaxor behavior. In BaZr x Ti 1Ϫx O 3 compounds, the relaxor behavior depends on the zirconium content.…”

Local piezoresponse and polarization switching in nucleobase thymine microcrystals

“…1(b)), i.e., different from the parameter b reported for thymine powder 38 (27.862 Å ). We hypothesize that significant structural distortions due to the presence of water in the crystal lattice might be an indication of the potential polar behavior [39][40][41] as will be experimentally delineated below.…”