Lead-free versus PZT: Acoustic characterization of ultrasonic immersion transducers fabricated with lead-free NBT-BT piezoceramic

An evaluation of the performance of a recently developed formulation of (lead-free) Sodium-Bismuth titanate - Barium Titanate (NBT-BT) piezoceramic is presented through the construction and testing of several immersion transducers based around a new material formulation "Pz12" from CTS Ferroperm (Kvistgaard, Denmark). Results are intended to yield insight into the applicability of this lead-free material for use within industrial, NDT, medical or underwater sectors through the reporting of experimentally realised performance characteristics. Results of several performance tests are reported including: pulse-echo amplitude, electrical insertion loss, transducer efficiency, power output and transmitting voltage response (TVR). Benchmarking is provided against comparable lead zirconate-titanate (PZT) based transducers using an industry standard Navy Type 1 (Pz26, CTS Ferroperm). Performance of the Pz12 transducers was found to exceed expectations, although was lower than that of the comparable Pz26 transducers. Pulse-echo amplitudes indicated a -4.3 dB relative amplitude between lead and lead-free variants with electrical insertion loss and transmitting voltage response both showing an average -3.1 dB between the Pz12 and Pz26. Electroacoustic conversion efficiencies of up to 52% are reported for the Pz12 transducers compared with a 62% maximum efficiency for the Pz26 variant. Temperature stability is also investigated in the 10-70 C range.