New electrostrictive ceramics for sonar projector applications.

Abstract

Relaxor ferroelectric ceramics, in particular lead magnesium niobate–lead titanate (Pb3MgNb2O9–PbTiO3) compositions, have potential for hydroacoustic transducer applications. In an unbiased state, the strain-versus-electric field relationship is nonlinear (largely quadratic) with respect to the electric polarization. By applying a large dc bias voltage simultaneously with a small ac signal, acoustic signals whose amplitudes are linear with respect to the ac signal are produced. The strains produced are of similar magnitude to those of lead zirconate–titanate ceramics. Several specific compositions have been examined in order to optimize the material by reducing the dielectric and electromechanical hysteresis, the temperature dependence of dielectric properties, and the dielectric aging and the results are discussed. The possibility of being able to switch the polarization of the material off with the biasing field makes the further development of these materials intriguing. [This work supported by ONR.]