Modified-lead-titanate/polymer composites for hydrophone applications

Abstract

Composite piezoelectrics made from Calcium-modified lead titanate rods embedded in a polymer matrix have been evaluated for hydrophone applications. These composites behave quite differently from the conventional 1–3 composites made with lead zirconate titanate ceramics. Specifically, in the modified lead-titanate case the magnitude of the d ₃₁ coefficient is enhanced in the composite structure, and consequently the hydrostatic d_h coefficient is suppressed. Nevertheless, these composites exhibit a large g_h coefficient and a remark able pressure stability. An analysis shows that a substantial contribution to the composite's d ₃₁ coefficient arises from internal stresses which develop along the ceramic rods and produce a piezoelectric charge through the d ₃₃ coefficient of the ceramic. This effect is particularly pronounced in the composite structure of the modified lead-titanate ceramic since the ratio d ₃₃/d ₃₁ in this ceramic is exceptionally large.