Preparation and simulation of lead free NBBT/epoxy 1–3 piezoelectric composites for high frequency medical ultrasound

This paper presents the modeling and fabrication of the (1-x)Na0.5Bi0.5TiO3-xBaTiO3 single crystal/epoxy 1–3 piezoelectric composite (NBBT 1–3 composite) with large electromechanical coupling factor (kt) for high frequency ultrasonic transducers. The NBBT 1–3 composite has been modeled by performing the finite element method using the COMSOL Multiphysics software. The parameters related to NBBT crystal are refined in the modeling process and the simulation results agree well with that of the experiment. The composite has been fabricated by the dice-and-fill method with a pitch of 12 μm. The measured resonance frequency, antiresonance frequency and electromechanical coupling factor (kt) with the values of 31.88 MHz, 43.16 MHz and 71.06% are obtained, respectively. The excellent performance of NBBT/epoxy 1–3 piezoelectric composite is comparable to that of lead-based Pb(Mg1/3Nb2/3)O3–PbTiO3/epoxy 1–3 piezoelectric composites. The excellent performance and the lead-free advantages make the NBBT/epoxy 1–3 piezoelectric composites quite attractive in high frequency medical ultrasound applications especially within the human body like intravascular ultrasound imaging (IVUS).