Calcium Nitrate Tetra-Hydrate-Doped Polyvinylidene Fluoride Thin Films as Potential Devices for Pressure Sensors

Calcium nitrate tetra-hydrate [Ca(NO₃)₂·4H₂O]-doped polyvinylidene fluoride (PVDF) thin films were successfully prepared by mixing 0.2-g-calcium nitrate into a PVDF solution under ultrasonification. The mixed solution was electrostatically spray coated onto aluminum foil substrates and then heat treated at 120 °C for 60 min in air. X-ray diffraction and Fourier transform infrared spectroscopy were used to confirm the crystal structure and chemical bonding conformation. A morphological characterization of the layers was performed using a scanning electron microscope. The dielectric properties of the samples were analyzed as a function of the variation of frequency. A piezoelectric characterization of the samples was performed by an electrical reaction of the layers after a single compression was applied from the impact of a pendulum. The structural and piezoelectric properties of the thin films could be related to the electroactive β phases in the Ca-doped PVDF thin films.