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Materials 2015, 8(12), 8195-8245; doi:10.3390/ma8125452

Elastic Properties and Enhanced Piezoelectric Response at Morphotropic Phase Boundaries

CNR-ISC, Istituto dei Sistemi Complessi, Area della Ricerca di Roma-Tor Vergata, Via del Fosso del Cavaliere 100, Roma I-00133, Italy
Academic Editor: Lorena Pardo
Received: 2 October 2015 / Revised: 13 November 2015 / Accepted: 18 November 2015 / Published: 2 December 2015
(This article belongs to the Special Issue Piezoelectric Materials)

Abstract

The search for improved piezoelectric materials is based on the morphotropic phase boundaries (MPB) between ferroelectric phases with different crystal symmetry and available directions for the spontaneous polarization. Such regions of the composition x − T phase diagrams provide the conditions for minimal anisotropy with respect to the direction of the polarization, so that the polarization can easily rotate maintaining a substantial magnitude, while the near verticality of the TMPB(x) boundary extends the temperature range of the resulting enhanced piezoelectricity. Another consequence of the quasi-isotropy of the free energy is a reduction of the domain walls energies, with consequent formation of domain structures down to nanoscale. Disentangling the extrinsic and intrinsic contributions to the piezoelectricity in such conditions requires a high level of sophistication from the techniques and analyses for studying the structural, ferroelectric and dielectric properties. The elastic characterization is extremely useful in clarifying the phenomenology and mechanisms related to ferroelectric MPBs. The relationship between dielectric, elastic and piezoelectric responses is introduced in terms of relaxation of defects with electric dipole and elastic quadrupole, and extended to the response near phase transitions in the framework of the Landau theory. An account is provided of the anelastic experiments, from torsional pendulum to Brillouin scattering, that provided new important information on ferroelectric MPBs, including PZT, PMN-PT, NBT-BT, BCTZ, and KNN-based systems. View Full-Text
Keywords: piezoelectricity; Morphotropic Phase Boundary; elasticity; polarization rotational instability; PZT; Pb-free ferroelectrics; anelasticity; domain walls piezoelectricity; Morphotropic Phase Boundary; elasticity; polarization rotational instability; PZT; Pb-free ferroelectrics; anelasticity; domain walls
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Cordero, F. Elastic Properties and Enhanced Piezoelectric Response at Morphotropic Phase Boundaries. Materials 2015, 8, 8195-8245.

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