Broadband ultrasound transducers using a plate with a graded piezoelectric constant formed by an internal temperature gradient

Broadband ultrasound transducers composed of a piezoelectric plate having a graded piezoelectric parameter are investigated. Grading of the piezoelectric constant e₃₃ is performed by giving an appropriate temperature gradient in the thickness direction of a fully-polarized piezoceramic plate which has a low Curie temperature. The broadband frequency characteristic of the proposed transducer is confirmed by experiments of wave generation in water by driving with a spike-shaped broadband electric pulse. The experimental results obtained for the graded plate with a matched backing clearly show the capability of launching a very short ultrasonic pulse and demonstrate the effectiveness of the piezoelectrical grading