Characterization of all the elastic, dielectric, and piezoelectric constants of uniaxially oriented poled PVDF films

Abstract

Polyvinylidene fluoride (PVDF), a piezoelectric material, has many useful applications, for example, as sensors, transducers, and surface acoustic wave (SAW) devices. Models of performance of these devices would be useful engineering tools. However, the benefit of the model is only as accurate as the material properties used in the model. The purpose of this investigation is to measure the elastic, dielectric and piezoelectric properties over a frequency range, including the imaginary part (loss) of these properties. Measurements are difficult because poled material is available as thin films, and not all quantities can be measured in that form. All components of the elastic stiffness, dielectric tensor, and electromechanical coupling tensor are needed in the models. The material studied here is uniaxially oriented poled PVDF that has orthorhombic mm2 symmetry. Presented are the frequency dependence of all nine complex elastic constants, three complex dielectric constants, and five complex piezoelectric constants. The PVDF was produced at Raytheon Research Division, Lexington, MA. Measurements were made on thin films and on stacked, cubical samples. The elastic constants c D 44 and c D 55 , the dielectric constants " T 11 and " T 22 , as well as the piezoelectric constants g15 and g24 reported here have not been published before. The values were determined by ultrasonic measurements using an impedance analyzer and a least square data-fitting technique.

Investigating the Effect of the Orthotropic Property of Piezoelectric PVDF

“…-Discrepancy between the reported piezoelectric properties is evident from Table 1. Furthermore, the material properties of PVDF have been measured using different techniques and used by different researchers [11,12]. Nevertheless, among the published data a satisfactory consistency has not yet been observed.…”

“…Nevertheless, among the published data a satisfactory consistency has not yet been observed. In order to implement the numerical simulations, in the present investigation the data measured and reported in reference [12] is adopted. The piezoelectric PVDF, which is commonly prepared in the form of thin films, is a semi crystalline polymer with a crystal volume fraction of about 50-60 % after melt extrusion.…”

PVDF-based ferroelectric polymers and dielectric elastomers for sensor and actuator applications: a review

“…The βphase can be obtained by several ways: mechanical stretching [15,22,23], electrical poling [15,22,23], high pressing [24][25][26], fast cooling [13,14,27], the addition of nanoparticles [17,[28][29][30][31]. As drawbacks, the PVDF material has anisotropic properties of the piezoelectric effect [32][33][34]. The piezoelectric performance along direction '2' of uniaxially oriented films is lower than along direction '1' due to its anisotropic semi crystalline structure (see figure 1(b)).…”

Shear Piezoelectricity of Poly(l-lactide) Films Manufactured by Extrusion–Orientation: An Insight on Process–Structure–Property Relationships

“…Note that PLA is nonferroelectric and a macroscopic polarization is only obtained with the application of shear stresses/strains. Piezoelectric coefficients d 14 in the range 10–20 pC/N are reported for uniaxially stretched poly­( l -lactide) (US-PLA) films ,,,− and, due to a low dielectric permittivity, shear piezoelectric voltage coefficients g 14 up to 350–800 mV·m/N are attested. ,, These piezoelectric performances are competitive with PVDF ( g 31 ≈ 200 mV·m/N, − g 33 ≈ 500 mV·m/N), ,,,, and multiple smart applications were demonstrated for piezoelectric PLA films/fibers (osteo-regeneration, biomedical catheters/tweezers, rotatory actuators, touch sensors, body movement sensors, etc. ). ,,,− Efficient piezoelectric energy harvesters based on a piezoelectric PLA layer were also recently developed, , and, based on simple electromechanical models, our group recently demonstrated competitive energy harvesting performances of US-PLA films compared to PVDF films .…”