Electroactive properties of polyamide/sodium niobate nanowires composites

Inorganic sodium niobate nanowires with high crystallinity were synthesized by an hydrothermal process. XRD study of these nanowires revealed a high crystallinity and an orthorhombic crystalline structure. This non centro-symmetric crystalline structure is responsible of the ferroelectric behaviour of these nanowires and by poling the samples above the glass transition of the matrix, the maximum piezoelectric coefficient of the composite was reached within 10 minutes. The magnitude of the poling field (10 kV/mm) is analogous with the one used for NN ceramics; i.e. significantly lower than for piezoelectric polymers (100 kV/mm). The optimum piezoelectricity is 6.5 pC/N for a PA 11/NN nanowires with φ = 0.3. The piezoelectric activity of composite has been compared with PA11/BaTiO₃ composites. Piezoelectric activity is higher in PA11/NN nanowires than in PA11/BaTiO₃ composites. These lead free composites have a piezoelectric activity close to the one of PZT / polymer composites. These “green composites” could find some applications in flexible, environmentally friendly piezoelectric sensors and actuators.