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

In this paper, lead-free 0.965(K
_0.45
Na
_0.55
) (Nb
_0.96
Sb
_0.04
)O
₃
-0.0375Bi
_0.5
Na
_0.5
Zr
_0.85
Hf
_0.15
O
₃
(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
_t
= 0.7), high piezoelectric constant (d
₃₃
= 350 pC N
^-1
), relatively low mechanical quality factor (Q
_m
= 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(Zr
_1-x
Ti
_x
)O
₃
(PZT)-based transducers suggests that the lead-free material can serve as a promising alternative to Pb-based piezoelectric materials for ultrasonic applications.