Sound Engineer's Pocket Book, 2nd Edition

27  Ultrasonics

Piezoelectric Transducers

Natural materials: quartz, SiO₂.

Synthetic materials include certain plastics and ceramics containing lead zirconate and titanate (PZT). The latter have to be electrically polarized by placing them in a strong electric field. For this reason they are known as ‘ferroelectrics’ by analogy with the magnetization of a ferromagnet. Four constants characterize the performance and efficiency of piezoelectric transducers:

1.  Bandwidth, Q

where f_fun = the fundamental resonant frequency, and f_a and f_b are the frequencies at which the transducer output amplitude falls to of the amplitude at f_fun.

Figure 144