Design of piezocomposites for ultrasonic transducers

1-3 piezoelectric-rud/passive-marriX composites offer advantages over the conventional pieuxzramics and piempolymers for the pulse-echo transducers used in medical ultrasonic imaging. Their benefits include high electmmednnical coupling, acwstic impedance close to that of tissue, a wide range of dielectric constants, low dielectric and mechanical losses, an adjustable sound speed, low coupling to spurious oscillations, ease of subdividing into acoustically isolated array elements. and formability into complex curved shapes. Not all benefits are achieved simultaneously. In designing a material for a specific epplication, the material engineer can choose the piezoceramic. the passive matrix, their relative proponions and the spatial scale of the composite. We delineate the trade-offs in designing piemcomposites which enhance the performance of present ultrasonic transducers as well as make new transducer designs feasible.