Introduction

Abstract

The piezoelectric effect, discovered by the Curie brothers in 1880, is the foundation of modern diagnostic ultrasound. When an electrical voltage is applied to a small, thin crystal plate having an asymmetrical crystal lattice, the plate will respond by undergoing a change in thickness. Accordingly, an alternating voltage will excite the crystal to undergo rhythmic volume changes, which are transmitted to the environment as pressure waves. This effect is reversible, i. e., mechanical deformation of the polar crystal element, caused for example by incident sound waves, will alter the electrical charge on the crystal surface. Because of these phenomena a single crystal element can serve as both a transmitter and a receiver of ultrasound waves, in effect becoming an electromagnetic transducer.