Preparation and Characterization of Large-Area and Flexible Lead Zirconate Titanate/Polyvinyl-Butyral/Additives Composite Films for Piezoelectric Sensor Application

To satisfy the requirement of structural health monitoring (SHM) using light sensors with high sensitivity, novel large-area and flexible lead zirconate titanate (PZT)/polyvinyl-butyral (PVB)/additives composite films were fabricated by the tape casting method. The microstructure and the piezoelectric and dielectric properties of the PZT/PVB/additives composite films were investigated systematically. Owing to the additives (dibutyl phthalate + castor oil), the flexibility and uniformity of the PZT/PVB composite films were improved significantly compared with conventional PZT/ PVB composite films. Moreover, the surfaces of the PZT/PVB/additives composite films are smooth and highly resistant to cracking. Scanning electron microscopy (SEM) was adopted to analyze the microstructure of the films. The microstructure analysis shows that microholes exist in the PZT/PVB composite films and an agglomeration phenomenon is noticeable. In contrast, PZT particles are well dispersed in the PVB matrix and there are few obvious microholes in the PZT/PVB/additives composite films. Furthermore, from energy-dispersive spectroscopy (EDS) results, it can be concluded that PZT particles were deposited at the bottom surface of the PZT/ PVB composite films. However, uniform deposition of PZT particles is achieved in the PZT/PVB/ additives composite films. In addition, owing to the additives, the improvement of the piezoelectric and dielectric properties of PZT/PVB/additives composite films is observed at a high volume fraction of PZT [phi (PZT) > 60%]. At phi (PZT) = 85%, the largest piezoelectric constant (d(33)) reaches 44 pC/N, which is much higher than that of the reported PZT/PVDF films and PZT/PVB films. Moreover, the dielectric constant (epsilon(r)) of the PZT/PVB/additives composite films (at room temperature and a frequency of 1 kHz) is higher than that of the PZT/PVB composite films with the same phi (PZT), and the dielectric loss (tan delta) is lower. Both the improved piezoelectric and dielectric properties are desirable for new piezoelectric sensor applications.