Enhancement piezoelectricity in poly(vinylidene fluoride) by filler piezoceramics lead-free potassium sodium niobate (KNN)

Abstract

Polymer–ceramic piezoelectric composites are promising materials for sensor and actuator, because of large piezoelectric response properties. Thin films composites of poly(vinylidene fluoride) (PVDF) and piezoceramics potassium sodium niobate (KNN) have been prepared by cast method on indium–tin-oxide-coated glass substrates. The β-phase in PVDF is responsible for piezoelectric property. KNN with different concentrations was used as filler in composites. Corona poling method is used to the polarized the thin films of PVDF/KNN composites. The morphology of thin films determines using SEM and the crystalline structure investigates by XRD and FTIR techniques. SEM shows the rough surface contained spherulitic structural with less porosity and the size of the spherulitic range between 1 and 3 μm in diameter. XRD demonstrated that the structure of pure PVDF film is mix of α and β-phase and converted to the pure β-phase after filler by KNN. FTIR results confirmed the XRD. The fraction β in PVDF films alter from 77.5 to 80.3 % after poling, and enhance to the 86.0 % by filler of KNN in PVDF.