An optimization of 1.3.1 PZT-polymer composite for deep underwater hydrophone application

Hydrophones stable up to a 10 MPa or 15 MPa hydrostatic pressure and with a g_hd_h figure of merit equal to 28×10^-12 Pa^-1 or 16×10^-12 Pa^-1, respectively, are proposed. These hydrophones are based on the 1.3.1 piezocomposite. For this kind of connectivity, there is no lateral contact between the polymer matrix and the PZT (lead zirconate titanate) rods. The PZT rods are inserted in holes made in the polymer matrix and are held between two metallic armature plates. The hydrophone sensitivity and figure-of-merit variations versus the hydrostatic pressure are related to the dependence of the PZT piezoelectric coefficients on the uniaxial stress applied along the polarization direction. An optimization approach is proposed based on a complete characterization of the PZT under uniaxial stress and a finite-element model of the piezocomposite. The optimization showed that the Navy III type PZT was most suitable for 1.3.1 piezocomposite hydrophones. Figures of merit up to 30×10^-12 Pa^-1 could be reached while keeping a good pressure stability up to 15 MPa