Application of Bonded Multilayer Technology to Relaxor-Based Single Crystals for Imaging Transducer Applications

摘要

The objective of this program was to evaluate the performance of single crystal materials processed in the form of multilayer crystals and crystal-composites. These multilayers have been fabricated using a process originally developed for polycrystalline ceramic. All of the multilayers were found to function with the expected four- and nine-fold increase in the effective dielectric constant. The coupling was found to vary considerably between different multilayer sizes and between different array element samples diced from the same multilayers. SEM analysis of the multilayers and of bulk material found evidence of crystal defects which likely contributed to some degradation in performance. The crystal- and crystal-composite multilayers were found to be considerably better than similar multilayers fabricated with ceramic materials. The KLM model has been used to predict the performance of array elements. Using the measured properties for 2-layer crystals and 3-layer crystal-composites, very wide bandwidth (> 120%) and very good insertion loss (- 18 dB) have been modeled. Because of the lower coupling measured for the crystal-composites, they did not show better bandwidth or sensitivity than the multilayer crystal. Improvements in crystal quality and a corresponding decrease in processing damage should improve the performance of multilayer crystal- composites, resulting in even better array performance.