Functional grading of a piezoelectric 1-3 composite for ultrasound transducers with enhanced axial and lateral resolution

A new approach for increasing the resolution capability of an ultrasound transducer in both axial and lateral directions is presented. A functionally-graded piezoelectric composite of 1-3 connectivity is newly devised and applied to a weighted conical transducer. In this piezocomposite material, the electric field for the wave excitation is effectively graded in the thickness direction, and this makes it possible to launch an almost single-pulse ultrasound wave. Because of the flexibility, this composite material can be formed easily into a conical shape and lends itself to enhance the time resolution of a conical transducer that possesses good lateral resolution over a large depth. The experimental results obtained for the fabricated transducer show the capability of launching a short ultrasonic pulse and creating a focal field over a large depth