Lead-free KNLNT piezoelectric ceramics for high-frequency ultrasonic transducer application

Abstract

This paper presents the latest development of a lead-free piezoelectric ceramic and its application to transducers suitable for high-frequency ultrasonic imaging. A lead-free piezoelectric ceramic with formula of (K 0.5Na 0.5) 0.97Li 0.03(Nb 0.9 Ta 0.1)O 3 (abbreviated as KNLNT-0.03/0.10) was fabricated and characterized. The material was found to have a clamped dielectric constant ε 33 S/ ε 0 = 890, piezoelectric coefficient d 33 = 245 pC/N, electromechanical coupling factor k t = 0.42 and Curie temperature T c > 300 °C. High-frequency (40 MHz) ultrasound transducers were successfully fabricated with the lead-free material. A representative lead-free transducer had a bandwidth of 45%, two-way insertion loss of -18 dB. This performance is comparable to reported performances of popular lead-based transducers. The comparison results suggest that the lead-free piezoelectric material may serve as an alternative to lead-based piezoelectric materials for high-frequency ultrasonic transducer applications.