Lead-Free Ceramics in Prestressed Ultrasonic Transducers

Todays ultrasonic transducers find broad application in diverse technology branches and most often cannot be replaced by other actuators. They are typically based on lead containing piezoelectric ceramics, which should be replaced for environmental and health issues by lead-free alternatives. Multiple material alternatives are already known, but there is a lack of information about their technological readiness level. Within this study a small series of prestressed longitudinally vibrating transducers was set up with a standard PZT material and two lead-free variants. The process for building the transducers beginning from the characterization of individual ring ceramics, over burn-in results, free vibration characterization by admittance and vibration measurements, and operation under load are documented. The main result is that the two investigated lead-free materials are ready to use within ultrasonic bolted Langevin transducers (BLT) for medium power range. Since they need higher voltage to achieve the same power level, driving electronics or mechanical setup have to be altered specifically for each material for optimum system setup. Lower self heating of the lead-free material might be attractive for heat sensitive processes.