7. Conclusions and Future Perspectives

In this monograph, we described detailed information regarding characteristics of high-frequency piezoelectric composites and the associated transducers and arrays. For high frequency ultrasound applications, piezoelectric composite exhibits its advantages arising from well-known properties such as higher electromechcanical coupling factor (k_t >∼0.65), lower acoustic impedance (<∼19 MRayl), lower mechanical quality factor (<50), and better flexibility than ceramic and crystal counterparts (elastic stiffness <40 GPa).