Lead free piezoelectric ceramics for medical ultrasound transducers

The potential of eliminating lead-based materials is gaining momentum in Europe, resulting in a search to replace PZT ceramics with comparable alternatives. Compositions based on the KNN and BNBK families have been reported to possess properties near PZT, and a comparison of the properties is given. Single element transducers operating at 5 MHz have been modeled and made using both compositions and PZT-5H. Bandwidths of nearly 40% were obtained for all transducers with single matching layers, and pulse-echo amplitudes were within 3 dB. Subsequent modeling of an array element shows a larger difference between PZT and the lead-free materials due to the lower clamped permittivity and k ₃₃' of those materials. Multilayer lead-free arrays could improve system efficiency though in the short term replacement could be more easily achieved in high frequency single element devices.