Large field-induced strains in a lead-free piezoelectric material

Abstract

Piezoelectric materials exhibit a mechanical response to electrical inputs, as well as an electrical response to mechanical inputs, which makes them useful in sensors and actuators. Lead-based piezoelectrics demonstrate a large mechanical response, but they also pose a health risk. The ferroelectric BiFeO(3) is an attractive alternative because it is lead-free, and because strain can stabilize BiFeO(3) phases with a structure that resembles a morphotropic phase boundary. Here we report a reversible electric-field-induced strain of over 5% in BiFeO(3) films, together with a characterization of the origins of this effect. In situ transmission electron microscopy coupled with nanoscale electrical and mechanical probing shows that large strains result from moving the boundaries between tetragonal- and rhombohedral-like phases, which changes the phase stability of the mixture. These results demonstrate the potential of BiFeO(3) as a substitute for lead-based materials in future piezoelectric applications.

Effect of crystal orientation on the phase diagrams, dielectric and piezoelectric properties of epitaxial BaTiO3 thin films

“…6(b) shows that (110)-orientated BTO films exhibit two huge responses across the boundaries of phase transitions, M B (r)-Tr(a 1 a 2 c) and Tr(a 1 a 2 c)-M A (r), which is promising for the design of piezoelectric sensors of compressive or tensile operating environment. 5 Enhanced piezoelectric responses are largely attributed to extrinsic mechanisms, such as domain wall motion, 52 and thus are not intrinsic. As for (111) orientation shown in Fig.…”

Electric control of straight stripe conductive mixed-phase nanostructures in La-doped BiFeO3

“…Because the relevant competing phases have quite different c-axis lattice parameters, as much as 10% while still being fully epitaxial without cracks or grain boundaries, electric control of the tetragonal-rhombohedral (T-R 0 ) phase boundary (T-R 0 PB) holds promise for very large electromechanical responses. 7,19 Particular attention has been paid to carefully unveil the exact crystal structures of these two constituent phases in the presence of complex mechanical deformation and strain gradient within the mixed-phase areas. Damodaran et al 20 have described the R 0 -and T-phase as monoclinic structures, denoted by M I and M II , respectively, and Chen et al 21 have introduced triclinic distortions to describe them.…”

Large resistivity modulation in mixed-phase metallic systems

“…An analogous response caused by mixed-phase coexistence in non-magnetic, uncorrelated oxides is found in the relaxor family of ferroelectrics, in which large dielectric and piezoelectric responses are observed near morphotropic phase boundaries 9,10 . In thin-film BiFeO 3 , epitaxial strain leads to the formation of a nanoscale, mixedphase ensemble of two crystal structures that can be reversibly transformed between each other with electric fields, leading to large piezoelectric responses 11,12 . Although these examples (as a direct consequence of mixed-phase coexistence) all occur in systems that are insulating (at least until chemically doped), we extend the same concept to metallic systems of FeRh in this report.…”