  1-3 type, 1-3-2 type and 2-1-3 type piezoelectric composites are three proper
smart materials for the design and manufacture of ultrasonic transducers. They
have been proposed in different stages but possess similar properties. Compared
with the initial 1-3 type composite, 1-3-2 composite is of higher mechanical
stability. Compared with 1-3-2 composite, 2-1-3 composite has lower
manufacturing difficulty. In this paper, a comparative study on these three
composites in terms of receiving transducer material properties is presented.
Finite element method (FEM) has been adopted to calculate longitudinal
velocity, thickness electromechanical coupling coefficient and voltage
receiving sensitivity. It is concluded that for a large aspect ratio
$\alpha=1$, the performance of 2-1-3 composite transducer is much better than
that of 1-3 and 1-3-2 composite transducers. The thickness electromechanical
coupling coefficient of 2-1-3 composite transducer is about 5.58 times that of
1-3 composite transducer and 7.42 times that of 1-3-2 composite transducer. The
voltage receiving sensitivity at 2 kHz of 2-1-3 composite transducer is 13.1 dB
higher than that of 1-3-2 composite transducer and 12.3 dB higher than that of
1-3 composite transducer.
