Tuned dielectric, pyroelectric and piezoelectric properties of ferroelectric P(VDF-TrFE) thin films by using mechanical loads

Abstract

Using the phenomenological Landau thermodynamic theory, we have investigated the effect of external mechanical loads on the phase transition and physical properties of poly(vinylidene fluoride-trifluorethylene) [P(VDF-TrFE)] thin films. Quantitative calculation shows that the phase transition temperature, polarization, dielectric, pyroelectric, and piezoelectric properties are highly sensitive to external mechanical loads. External compressive stress increases the phase transition temperature and the out-of-plane polarization and decreases the out-of-plane dielectric constant below Tc, pyroelectric coefficient, and piezoelectric coefficient (absolute value) and vice versa. Compared with pervoskite-type ferroelectrics, the calculated results are opposite due to the different intrinsic parameters between pervoskite and polymer ferroelectrics, especially, electrostrictive constants. The ability to tailor the properties in ferroelectric P(VDF-TrFE) thin films with the mechanical load can offer a tremendously promising future for applications in multifunctional devices, such as agile mechanical sensors and transducers.