Dielectric properties of the parylene-C based doped piezoelectric materials

Recent technological advancements have significantly increased the daily use of electrical energy, thereby making energy storage applications a critical area of research. Dielectrics, being suitable materials for energy storage, underscore the importance of understanding their dielectric properties. Parilen-C, a piezoelectric polymer, emerges as a potential material for these applications due to its superior electrical, physical, and chemical properties. While previous studies aimed to enhance the dielectric properties of polymer materials by adding ceramics, oxides, or metals, this thesis focuses on synthesizing Parilen-C polymer via chemical vapor deposition and investigating the dielectric properties of composites produced by adding varying proportions of polyurethane (PU), polymethyl methacrylate (PMMA), and activated carbon. While studies exist on examining the dielectric properties of composites using pure or other added materials, this thesis represents the first examination of composites produced in this manner. The dielectric properties of the produced samples were examined in the 1-10 MHz frequency range. Measurements including capacitance, dissipation factor, impedance, resistance, and reactance were conducted using an impedance analyzer, and dielectric permittivity and losses were calculated. Subsequently, the samples were polarized, and their dielectric properties were re-measured. The measurements revealed resonance frequencies of the materials within the tested frequency range and their responses at these frequencies, showing inductive behavior at frequencies higher than the resonance frequency. Changes in resonance frequency were observed following the additions made, both increasing and decreasing. While increases in dielectric permittivity were observed in some samples after polarization, increases in dielectric loss were much more significant. The dielectric permittivity value showed an increase of up to 5.58 times in the resonance frequency region after polarization, reaching a maximum value of 246, whereas dielectric loss values increased up to 20,000 times in some samples, reaching up to 5000. Since dielectric loss values increased as they approached the resonance frequency, this indicates that the losses obtained are higher than those required for metamaterial applications. The capacitive and inductive behaviors exhibited by the material were also illustrated in impedance, resistance, and reactance graphs. Cole-Cole plots were created using resistance and reactance values, and analyses were conducted regarding the distribution and structural properties of the material. It was observed that the materials exhibited a perfect semicircle, and the α values, were calculated to make comparisons about the homogeneity of the samples.