Piezoelectric and Dielectric Properties of PZT-Epoxy Composite Thick Films

Ferroelectric films have been of interest over the last 20 years because of the possibility of using them for non-volatile memory applications [1-3], MEMS [4-6], ultrasonic devices [4,7], battery separators [8-10], biomedical scaffolds [11] and energy harvesting devices where they are coupled with batteries [12]. The properties if piezoelectric films cannot be compared directly with those of bulk materials of the same composition because their processing and electrical properties differ. Previous work on the preparation of piezoelectric films includes RF planar magnetron sputtering [13,14], ion beam sputtering [15] or DC magnetron sputtering [16], where most recently, researchers have succeeded in fabricating films using various chemical methods of deposition such as; metal organic chemical vapor deposition (MOCVD) [1719], chemical solution deposition [20,21], metalorganic decomposition (MOD) [22,23], and also pulsed laser deposition (PLD) [24-26]. The sol-gel method has the benefits of compositional control, reduced temperature processing of highly uniform, dense, crack-free films and low cost of fabrication [27,28]. These methods of processing ferroelectric films have been used with notable success to produce piezoelectric ceramic films comprised of Lead Zirconate Titanate (PbZrxTi1-xO3 also known as, PZT). PZT has a high dielectric constant, ferroelectric, piezoelectric, and pyroelectric properties. The ideal properties of PZT have made its application to transducer, sensor and actuator devices ubiquitous. However, the poor mechanical strength of these devices has limited their life cycle and performance. Therefore, interest in polymer-ceramic [29-33] (and ceramicceramic [34,35]) composites has emerged as an area of interest because polymers are flexible, low cost, easily processed [36,37] and able to be polarized under the influence of an external electric field [38].