Radially Sandwiched Composite Transducers Composed of the Radially Polarized Piezoelectric Ceramic Circular Ring and Metal Rings

A new type of radially sandwiched composite piezoelectric transducers is developed and its radial vibration is studied. The transducer is composed of two metal rings and a radially polarized piezoelectric ring which is sandwiched between the inner and outer metal rings. The electromechanical equivalent circuits of the piezoelectric and metal rings in radial vibration are introduced. Based on the mechanical boundary conditions, a three-port electromechanical equivalent circuit for the radially sandwiched composite transducer is obtained and the frequency equation is given. The dependence of the resonance/anti-resonance frequency and the effective electromechanical coupling coefficient on the geometrical dimensions of the composite transducer is theoretically obtained. The radial vibration of the transducer is simulated by using finite element method. The resonance and anti-resonance frequencies of the composite transducers are measured. It is shown that the analytical, numerical and experimental resonance and anti-resonance frequencies are in good agreement with each other. This type of transducers can be used as two-dimensional emitter and receiver in ultrasonic and underwater sound applications.