1-3 single-crystal composites for ultrasonic transducer arrays

16801)ABSTRACTThe development of single crystal relaxor-PT piezoelectrics is an exciting advance in ultrasoundtransducer technology. The high electromechanical coupling coefficients and variable dielectric constant couldbe used to significantly enhance bandwidth and sensitivity of array transducers. In this study 1-3 composites ofsingle crystal material were engineered and applied to an array design. Both predicted and actual performancesare reported and compared to array designs using PZT-5H based 1-3 composite material.In order to take advantage of the performance enhancement of single crystal materials a 1-3 compositeconnectivity was selected. Two techniques were used to tile together small pieces of crystal into a largercomposite plate suitable for array applications. A coupling coefficient of .81 and an acoustic impedance of 15.6Mrayls were obtained using a 58% volume fraction of single crystal. A comparable PZT composite displayed acoupling coefficient of .66 and an acoustic impedance of 1 7.0 Mrayls. A sufficiently fine spatial scale resulted inlateral resonances being well above the thickness mode resonance for both materials.One-dimensional modeling using the Redwood equivalant circuit in PSpice was used to investigatematching and backing. An optimization scheme resulted in a modeled bandwidth of 134% and a -6 dB pulselength of only one cycle using a single front matching layer and a castable backing. Eight element arrays ofsingle crystal and PZT-5H composite were constructed to verify the theoretical results.KEYWORDS: Transducers, Single Crystal, Arrays, Piezoelectric Composites