Finite element modeling of transduction materials with application to piezoelectric hollow sphere transducers

Spherically focused transducers were prepared from miniature thin-wall lead zirconate titanate hollow spheres (BBs). The spheres were prepared from slurries of soft PZT powders using a coaxial nozzle process, and have diameters ranging from 1 to 6 mm and wall thicknesses from 12 to 150 μm. The two main vibration modes, the radial and wall thickness modes, were observed near MHz and 30-40 MHz, respectively. Focused transducers were prepared by machining sections of the hollow spheres. The transducers were characterized in the pulse echo mode and with the help of finite element analysis (FEA). The ATILA code has been adapted to take into account a coupled solid-piezoelectric problem in the time analysis. The results obtained from experiments were confirmed by FEA