Functionally graded piezoelectric ceramics for ultrasonic transducers

Functionally graded piezoelectric ceramics (FGM) plates are attractive due to their ability to broaden the frequency bandwidth of the ultrasonic transducers. A resistivity gradient La-doped Lead Zirconate Titanate/Al-doped Zinc Oxide (La-PZT/AI-ZnO) piezoelectric ceramics plate was developed using a powder metallurgical process. Grading of the piezoelectric modulus across the plate was experimentally confirmed by the electrical impedance analysis and its gradient distribution was characterized using the profile-technique. The distribution of Zn2+ ions in the PZT region was examined using EPMA, XRD and SEM/EDX, respectively. Analysis results show that the gradient distributions of structural and electrical properties inside the FGM plate are mainly caused by the diffusion and aggregation of Zn2+ ions in the PZT layer. The functionally graded piezoelectric ceramics plate presented here will be useful for broadening the frequency bandwidth of piezoelectric transducers.