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Review: commercialization of piezoelectric single crystals for medical imaging applications

Lead-based piezoelectric single crystals such as Pb(Zn1/3Nb2/3O3-PbTiO3 (PZN-PT) and Pb(Mg1/3Nb2/3O3- PbTiO3 (PMN-PT) have been extensively studied in the past several years due to their large piezoelectric properties. The high d33 (2200pC/N) and k33 (93%) values make them attractive for electromechanical applications, such as actuator, hydrophone, accelerometer, sonar-type transducers, and medical ultrasonic devices. This paper will briefly review recent progress in single crystal materials and device developments with a focus on medical imaging applications. Theoretical ultrasound transducer models indicate a dramatic bandwidth improvement when using PMN-PT or PZN-PT crystals to replace PZT ceramics. Prototypes showed that one single crystal transducer could cover frequency range of two traditional PZT ceramic transducers. Ultrasonic images demonstrate the advantage of single crystal based designs. The extended transducer bandwidth and sensitivity offers significant performance advantages, particularly in penetration and imaging resolution. Philips released the first commercial single crystal transducers to the customers in November 2004, and received excellent market acceptance. For broader applications, the concerns and limitations of using single crystal materials in electromechanical devices are also discussed in this article.