Characterization of PZT hollow-sphere transducers

Millimeter size, hollow spheres of lead zirconate titanate have been fabricated by blowing gas through a fine-grained slurry of PZT-5. Techniques were developed for the classification of defects in green and sintered spheres. The spheres were poled radially between inner and outer electrodes. The dielectric and piezoelectric properties were characterized for poled spheres. The two principal resonances were a breathing mode near 700 KHz and a wall thickness mode near 10 MHz. Hydrostatic d_h coefficients ~1000 pC/N were measured. Pulse-echo measurements were also performed to characterize transducer performance. Potential applications for these miniature omnidirectional transducers include biomedical imaging, flow noise sensors and hydrophones