Current Status and Future Prospects of Piezoelectric Single Crystals and
Their Composites: “Lead-based” and “Lead-free”

Crystallographically engineered Relaxor-PT single crystals, specifically PMN-PT and PZN-PT, offer much higher piezoelectric and electromechanical coupling coefficients (d33>1,500 pC/N, k33>0.9), when compared to PZT ceramics. Therefore, the high performance piezoelectric single crystals have been expected to replace polycrystalline PZT ceramics in many application fields such as ultrasound transducers (medical and NDA), SONAR transducer, piezoelectric actuators, piezoelectric sensors, ultrasonic motors, piezoelectric composites and piezoelectric energy harvesting, etc.
Recently the solid-state single crystal growth (SSCG) technique for fabricating the high performance “lead(Pb)-based” piezoelectric single crystals such as PMN-PT and PMN-PZT has been successfully developed. Compared to conventional single crystal growth methods such as flux and Bridgman methods, the SSCG process is very cost-effective and suitable to mass production because a complicated melting process is not involved in the SSCG process. And the SSCG method was successfully applied to growth of high performance “lead(Pb)-free” piezoelectric single crystals (d33>1,500 pC/N, k33>0.9).
In this presentation the recent progress on development and application of “lead-based” and “lead-free” piezoelectric single crystals [wafers, wedges, rings, 1-3 and 2-2 composites, and SFC (single crystal fiber composite)] will be introduced, as shown in Fig. 1.
Fig. 1. PMN-PT/PMN-PZT single crystals: wafer, wedge, 1-3 composite ring, and SFC