Development of novel 1-3 piezocomposites for low-crosstalk high frequency ultrasound array transducers

The goal of this research was to develop a novel diced 1-3 piezocomposite geometry to reduce pulse-echo ring down and acoustic cross-talk between high-frequency ultrasonic array elements. PZT-5H based 1-3 composites (10 and 15 MHz) of different pillar geometries (square (SQ), 45° triangle (TR), and pseudo-random (PR)) were fabricated and then made into single element ultrasound transducers. The measured pulse-echo waveforms and their envelopes indicate that the PR composites had the shortest -20 dB pulse length and highest sensitivity among the composites evaluated. Using these composites, 15 MHz array sub-apertures (0.95 lambda pitch) were fabricated to assess the acoustic cross-talk between array elements. The combined electrical and acoustical cross-talk between the nearest array elements of the PR array sub-apertures (-31.8 dB 15 MHz) was 6.5 dB and 2.2 dB lower than that of the SQ and the TR array sub-apertures, respectively. To further reduce inter-element cross-talk of kerfless annular array transducers, utilizing the piezocomposites with the PR pillar geometry, we fabricated high-frequency annular arrays. Each annular array was designed to have six equal-area elements and a center frequency of 40 MHz. The average center frequency estimated from the measured pulse-echo responses of array elements was 38.7 MHz and the -6 dB bandwidth was 51%. The average insertion loss recorded was 23.1 dB, and the maximum combined crosstalk between the adjacent elements was less than -31 dB. These results demonstrate that the 1-3 piezocomposite with the pseudo-random pillars may be a better choice for fabricating enhanced high frequency linear array ultrasound transducers; especially when mechanical dicing is used.