Piezoelectric materials is a class of Smart Materials due to their ability to perform both sensing and actuating functions.  Sensors and mechatronic devices based on piezoelectric materials have been developed in the Centre for Smart Materials of The Hong Kong Polytechnic University for applications in various engineering disciplines. Devices that have been developed in the Centre include micro-machined Si-based acoustic sensors and piezoceramic fibre/epoxy 1-3 composite impact force sensors for industrial process control, smart transducers for ultrasonic wirebonding, high-frequency transducers for medical ultrasound, actuators for active vibration control and piezoelectric transformers.

Recently lead-free piezoelectric ceramics have attracted considerable attention because of environmental protection reasons. The WEEE (The Recycling and Recovery Directive or the Waste Electronic Electrical Equipment) and RoHS (Restriction of Hazardous Substances) have strongly discouraged the use of lead in many commercial applications and materials (e.g. in solder, glass and pottery glaze). Intensive searches have been conducted by many researchers to find suitable lead-free piezoelectric ceramics to replace the commonly used lead-zirconate-titanate (PZT) ceramics. The effort of our group in fabricating piezoelectric devices including high-frequency transducers, accelerometers and cymbal actuators based on BNT-0.05BKT-0.05BT lead-free ceramics will be described.