High frequency 1-3 composite transducers fabricated from alkoxide-derived PZT fibers

Research in obtaining higher frequency 1-3 composite transducers for ultrasonic imaging applications has prompted the need for finer scale composite structures. Fine scale fibers of lanthanum doped lead zirconate titanate (PLZT) were derived from a continuous alkoxide based sol-gel spinning process for incorporation into 1-3 type composites. Single fiber filaments, ranging from 10 to 60 μm in diameter, were fabricated. Microstructural and electrical characteristics of these fibers were determined under different pyrolysis and sintering conditions to obtain high quality dense fibers with dielectric constants up to 1100. Fibers were then incorporated into 1-3 composites using an epoxy matrix with volume fractions ranging from 10 to 40%. Resonance frequencies between 15 and 40 MHz could be obtained with thickness coupling coefficients up to 70%. Transducers were fabricated using these composites and evaluated for their pulse/echo characteristics. These transducers, without optimization, had center frequencies of 40 MHz with a bandwidth of 54% and a round-trip insertion loss of 47 dB