CHARACTERIZATION OF LEAD ZIRCONATE TITANATE CERAMICS FOR USE IN MINIATURE HIGH-FREQUENCY (20-80 MHZ) TRANSDUCERS

The development of new endoscopic applications of ultrasound imaging is critically dependent on the availability of efficient broadband transducers with areas of 2 mm2 or less. The material properties of PZT ceramics for operation in the thickness mode at frequencies as high as 80 MHz are reported. Each of the ceramics tested showed a reduction in k(t) with increasing frequency. In a fine grained PZT, values of k(t) as high as 0.44 were measured at 80 MHz. The effects of grain size were also evident in the measurement of frequency dependent mechanical losses. Experimental and theoretical analysis of 1 mm2 45-MHz PZT transducer verified the validity of the properties measurements and demonstrated excellent insertion loss and bandwidth characteristics. The minimum insertion loss of -17.5 dB is in good agreement with theory and is a marked improvement over the performance of polymer devices. Details on the fabrication and testing of high frequency ceramic transducers are described.