Transducers Using Forced Transitions Between Ferroelectric and Antiferroelectric States

Abstract : The use of resonant piezoelectric composite structures for acoustic radiation into fluid media is well established. At low frequencies, desirable for long distance acoustic transmission, resonant structures are extremely large and expensive. Frequency lowering can be accomplished by a variety of means involving use of bending structures or mass-loading, but the resulting transducers are vulnerable to pressure effects due to deep submersion. A possible alternative to present transducer structures is the use of the electric field-forced transition from antiferroelectric to ferroelectric. A number of Pb(Zr, Sn, Ti)O3 compositions have been developed which experience these transitions at relatively low electric field(7-15 kV/cm) and typically generate volume strains near 0.1%. There is therefore not necessarily a requirement for acoustic shielding, and since the developed strain is independent of frequency, resonant structures are not needed. Construction is therefore simplified and the size and weight of low frequency transducers may be reduced. Operating characteristics of the antiferroelectric transducer are discussed in detail, but no large low frequency transducer arrays have yet been built.