New materials for large strain sonar applications

Several new materials capable of generating large strains by the application of an electric field are being developed for applications as actuators and high-drive sonar projectors. These materials are capable of generating strains which are an order of magnitude larger than those produced by conventional lead zirconate-titanate ceramics. The first group of materials are the class of lead magnesium niobate-lead titanate (PMN-PT). These materials are electrostrictive and, therefore, are operated under dc bias fields. The largest strains are obtained when the temperature is maintained in the region of the order-disorder phase transition of the material. This, however, makes the properties of the material somewhat temperature dependent. Recent advances have developed a material with extremely low losses which can be used as a sonar projector or an actuator. Results are presented of measurements on several compositions of PMN-PT which are believed to be the best candidates for actuator and transducer applications