Frequency dispersion and field dependence in the material constants of PVDF-TrFE copolymers in the thickness mode

A set of thickness resonators of PVDF-TrFE copolymer have been characterized as a function of the frequency and DC bias. The first six resonance peaks in the impedance spectra were analyzed to determine the degree of frequency dispersion in the complex elastic, piezoelectric, and dielectric constants. Modeling the dispersion in the material constants as a polynomial in the frequency f produced an excellent fit to the data over the 1-30 MHz frequency range. The samples were then tested for non-linearity by analyzing the fundamental resonance as a function of a DC bias field. The field dependence of the PVDF-TrFE samples was much smaller than for comparable samples of a soft PZT.