Enhanced electromechanical properties of piezoelectric thin flexible films

Highly flexible piezoelectric 0-3 PZT/PDMS (lead zirconate titanate–poly dimethyl siloxane) composites incorporated with carbon nanotubes (CNT) and carbon black (CB) were fabricated by solution casting technique using a constant PZT/PDMS ratio of 40/60 and conductive fillers ranging from 0 to 0.5 vol.%. Impedance measurements proved that a small addition of conductive fillers sufficiently enhanced the electrical conductivity to lead to improved poling efficiency. For too high volume fractions (and consequently too high conductivity), poling becomes impossible. For the optimum PZT/PDMS/0.125CNT a relative permittivity εr ∼ 50 and conductivity σ ∼ 2.8 × 10−6 S/m was obtained while for the optimum PZT/PDMS/0.125CB εr ∼ 35 and σ ∼ 1.9 × 10−6 S/m have been realized. The piezoelectric charge constant d33 of the PZT/PDMS/0.125CNT and PZT/PDMS/0.125CB composites were 25 and 18 pC/N, respectively. Dynamic mechanical analysis (DMA) shows better performance for PZT/PDMS/CB with lower volume fraction conductive fillers than for the PZT/PDMS/CNT composites. The excellent (di-)electrical properties and the relatively simple fabrication procedure of these polymer–matrix composites make them promising candidates in piezoelectric sensors, actuators and high efficiency capacitors.