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

摘要

Polyvinylidene fluoride (PVDF), a piezoelectric material, has manynuseful applications, for example, as sensors, transducers, and surfacenacoustic wave (SAW) devices. Models of performance of these devicesnwould be useful engineering tools. However, the benefit of the model isnonly as accurate as the material properties used in the model. Thenpurpose of this investigation is to measure the elastic, dielectric andnpiezoelectric properties over a frequency range, including the imaginarynpart (loss) of these properties. Measurements are difficult becausenpoled material is available as thin films, and not all quantities can benmeasured in that form. All components of the elastic stiffness,ndielectric tensor, and electromechanical coupling tensor are needed innthe models. The material studied here is uniaxially oriented poled PVDFnthat has orthorhombic mm2 symmetry. Presented are the frequencyndependence of all nine complex elastic constants, three complexndielectric constants, and five complex piezoelectric constants. The PVDFnwas produced at Raytheon Research Division, Lexington, MA. Measurementsnwere made on thin films and on stacked, cubical samples. The elasticnconstants c44D and c55D, thendielectric constants e11T and e22Tn, as well as the piezoelectric constants g15 andng24 reported here have not been published before. The valuesnwere determined by ultrasonic measurements using an impedance analyzernand a least square data-fitting technique