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

In this paper, lead-free 0.965(KNa) (NbSb)O-0.0375BiNaZrHfO (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 ( k = 0.7 ), high piezoelectric constant ( d = 350 pC N), relatively low mechanical quality factor ( Q = 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(ZrTi)O (PZT)-based transducers suggests that the lead-free material can serve as a promising alternative to Pb-based piezoelectric materials for ultrasonic applications.