KNNS-BNZH Lead-Free 1-3 Piezoelectric Composite for Ultrasonic and Photoacoustic Imaging.

In this paper, lead-free 0.965(K0.45Na0.55) (Nb0.96Sb0.04)O3-0.0375Bi0.5Na0.5Zr0.85Hf0.15O3 (KNNS-BNZH)/epoxy 1-3 composite was designed and fabricated with the dice-and-fill method. The composite material exhibited a high thickness electromechanical coupling coefficient ( kt = 0.7 ), high piezoelectric constant ( d33 = 350 pC N-1), relatively low mechanical quality factor ( Qm = 5 ), and relatively low acoustic impedance. An ultrasonic transducer with a center frequency of 5 MHz was produced based on the 1-3 KNNS-BNZH/epoxy composite, showing a broad bandwidth of 80% (-6 dB) and two-way insertion loss of -30 dB. Ultrasonic and photoacoustic images were further demonstrated. The outstanding performance of the 1-3 KNNS-BNZH/epoxy composite transducer competitive to Pb(Zr1-xTix)O3 (PZT)-based transducers suggests that the lead-free material can serve as a promising alternative to Pb-based piezoelectric materials for ultrasonic applications.