Lead-free thick piezoelectric films as miniature high temperature ultrasonic transducers

Thick piezoelectric lead-free bismuth titanate films have been successfully deposited on steel substrates with different shapes by a sol-gel spray technique. The center frequencies of ultrasonic signals generated by the bismuth titanate films on steel samples ranged from 5 to 30 MHz and their bandwidth was broad. The ultrasonic signals generated and received by these ultrasonic transducers had a signal-to-noise ratio of 25 dB at 200/spl deg/C in pulse/echo mode. This transducer can be as small as 1 mm in diameter.