Piezoceramics for high frequency (50 to 100 MHz) single element imaging transducers

The properties of transducer materials operating at high frequencies determine the level of performance which is achievable. Selection of the appropriate material can be made based on the transducer size and frequency. The properties of a number of piezoceramic materials have been experimentally determined by measuring the electrical impedance of air-loaded resonators whose thickness corresponds to resonance frequencies from 10 to 100 MHz. Materials measured include commercially available high dielectric lead zirconate titanate (PZT) and lower dielectric modified lead titanate (PT) ceramics, as well as materials which have been designed or modified to result in improved properties at high frequencies. Conclusions regarding the influence of the microstructure and composition on the frequency dependence of the properties are made based on the calculations and microstructural analysis of each material. Issues which affect transducer performance are discussed in relation to the measured properties. For larger area transducers the use of a lower dielectric constant material results in better electrical matching between the transducer and standard 50 Omega electronics. KLM model simulations show improved performance for transducers which are electrically matched.