Ultrasonic transducers with functionally graded piezoelectric ceramics

Ultrasonic transducers used for measurement systems are required having a capability of generating a short time waveform ultrasonic pulse, i.e., a broadband frequency spectrum. In order to obtain the broadband transducer, functionally graded piezoelectric ceramics with a ceramic backing are fabricated and their ultrasonic performances are examined. Gradient of the piezoelectric parameter is realized by sintering a layer-structured ceramic green body composed of piezoelectric ceramic calcined powder layers with various compositions or composed of green sheets containing calcined powder mixed with some organic materials. It has been found that the above transducer generates an ultrasonic wave with a broader frequency spectrum compared with that of the conventional one.