The growth， properties and applications of pmnt， a new piezocrystal

A feasible method to grow highquality large PMNT single crystals by the modified Bridgman technique has been set up on the basis of studies of the phase structure, phase stability and phase diagram of the PMNPT binary system at high temperature. Single crystals have been grown with a boule size of 40×70mm and plate size of 20×20×1mm3. The dielectric constant ε is ～5000, loss tan δ<09%, piezoelectric constant d33>1500pC/N,and coupling k33～94%. The crystals have great piezoelectric activity and unstable properties at a composition near the MPB where the crystal structure is very complex, so growth should take place far from the MPB. The single crystals have been successfully used in transducers for scanning electron acoustic microscopes, with clear improvement in the resolution of the electron acoustic images. These results indicate that PMNT single crystals are promising for applications in medical ultrasonic imaging, sonar transducers and high strain actuators.