THE OPTIMIZATION OF EXCESS Pb CONTENT IN SOL-GEL DEPOSITED SANDWICH STRUCTURE PbTiO₃/PbZr_0.3Ti_0.7O₃/PbTiO₃ THIN FILMS

ABSTRACT

The PbTiO₃/PbZr_0.3Ti_0.7O₃/PbTiO₃ (PT/PZT/PT) and PbZr_0.3Ti_0.7O₃ (PZT) thin films were prepared by sol-gel method. In order to optimize the excess Pb content in PT layers, different excess Pb content (x = 0, 0.05, 0.10, 0.15, 0.20) were added to the PT precursor to prepare the PT/PZT/PT films, and the films were annealed at 550∼700 °C for 20 min in O₂ atmosphere. The X-ray diffraction (XRD) results show that the pure perovskite structure PT/PZT/PT films can be obtained from the proper Pb/Ti ratio precursor solution (excess Pb content x = 0.10 and 0.15 in PT layers) and annealing temperature of 600∼700 °C. The results of the P–E hysteresis loops indicate that the most proper annealing temperature is 650 °C. Well-saturated hysteresis loops with higher remnant polarization (Pr) and lower conceive field (Ec) are obtained for the film with excess Pb content x = 0.15 in PT layers. The fatigue and leakage current properties indicate that the PT/PZT/PT thin film with excess Pb content x = 0.10 has the lowest fatigue rate and less leakage current density than other films. Considering the results of XRD, ferroelectric, fatigue and leakage current properties, the optimized excess Pb content (x) in PT layers and annealing temperature should be x = 0.10∼0.15 and 650 °C, respectively.

Keywords:

• ferroelectric PT/PZT/PT thin films
• sandwich structure
• excess Pb content
• PT seed layers

ACKNOWLEDGMENTS

This work is supported by the key program of National Nature Science Foundation of China, No. 90407023.