High frequency dielectric and electromechanical properties of ferroelectric nylons

Abstract

The first measurements of high frequency dielectric and thickness-mode electromechanical properties of ferroelectric nylons are reported. Two sets of nylon 11 film samples were produced. The first set was melt-quenched and poled, while the second set was melt-quenched and then cold-drawn at room temperature before poling, resulting in a three-dimensionally ordered sample. Gold electrodes, 10 mm by 10 mm, were evaporated on opposing sample surfaces. The remanent polarization of the unoriented sample was 27 mC/m/sup 2/ while that of the oriented sample was 52 mC/m/sup 2/. Samples of each film were placed in a programmable environmental chamber and connected to a Hewlett Packard 4195A Network/impedance Analyzer via a custom remote fixture. Broadband measurements were made of the clamped capacitance and dissipation factor, thickness-mode electromechanical coupling coefficient k/sub t/, mechanical quality factor Q/sub m/, and longitudinal sound velocity v/sub l/ for each sample over a temperature range of 20/spl deg/-160/spl deg/C. Comparisons of the properties were made between oriented and unoriented film samples. The results showed k/sub t/ values in the 0.03-0.11 range, and Q/sub m/ values of 8-10 above the glass transition temperatures of the samples (approximately 60-70/spl deg/C). The results show promise for high temperature ferroelectric nylon sensing applications.