| || Polymeric Piezoelectric Transducers for Hydrophone Applications
Author : Kharat, D. K.;Mitra, Sandhya ;Akhtar, Sania ;Kumar, Vijai
Source : Defence Science Journal ; Vol:57(1) ; 2007 ; pp 7-22
Subject : 66 Chemical Technology
Keywords : Piezoelectric materials;Polymeric materials;PVDF;Hydrophones;Acoustic signal;Pressure- release system;Ceramics;Voided PVDF;Sonar;Piezoelectric polymers;Transducers
Abstract : Conventional ceramic piezoelectric materials have been used in hydrophones for sonar applications since 1940's. In the last few years since the discovery of polymeric piezoelectric hydrophones, the technology has matured, applications have emerged in extraordinary number of cases such as underwater navigation, biomedical applications, biomimetics, etc. Hydrophones are used underwater at high hydrostatic pressures. In the presence of hydrostatic pressures, the anisotropic piezoelectric response of ceramic materials is such that it has poor hydrophone performance characteristics whereas polymeric piezoelectric materials show enough hydrostatic piezoelectric coefficients. Moreover, piezoelectric polymers have low acoustic impedance, which is only 2-6 time that of water, whereas in piezoelectric ceramics, it is typically 11-time greater than that of water. A close impedance match permits efficient transduction of acoustic signals in water and tissues. Newly developed hydrostatic-mode polyvinylidene flouride (PVDF) hydrophones use a pressure-release system to achieve improved sensitivity. Recently, voided PVDF materials have been used for making hydrophones having higher sensitivity and figure of merit than unvoided PVDF materials.