Dielectric and Piezoelectric Properties of Pb Perovskite Relaxor type Single Crystals by AC poling

Introduction Solid solution of Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) and the other relaxor ferroelectric single crystals (SCs) have attracted great research interest over the past decades owing to their outstanding piezoelectric and electromechanical properties, and widely applicated in sensors, transducers, and actuator technology. In order to improve the performance of ultrasonic (US) medical echo probes, a higher performance piezoelectric material is required, and relaxor SCs of PMN-PT have been considered as a promising material for next generation transducers for medical echo and some of medical probes have already been commercialized with PMN-PT SCs due to relatively higher piezoelectric constant d33 > 1500 pC/N, which is nearly twice that (d33<900 pC/N) of traditional lead zirconate titanate (PZT) ceramics. In general, the growth method of PMN-PT SCs is one charge Bridgman (OC BM) method. To solve the compositional segregation, JFE Mineral Co. Japan developed new SC growth method named continuous-feeding Bridgman method (CF BM), and this method can control the melt composition during crystal growth process and improve the composition uniformity. Recently, Yamamoto and Yamashita et al., reported dynamic AC poling (ACP) can enhanced 20 to 100% of the dielectric and piezoelectric properties of SCs compared to conventional statice DC poling (DCP). After these reports, many researchers have investigated the ACP research in the world. When piezoelectric materials suffer the abrupt changes in external conditions such as temperature and biasing filed etc, gradual changes in its electrical and physical constants with time will occur, which called aging rate (AR) of materials. For medical US echo probes, the larger AR of crystals resulted in deteriorating US imaging qualities and the shorter service life of these probes. The AR of ferroelectric ceramics have been reported by many researchers. However, there is a few studies on the AR of PMN-PT based relaxor SCs. Therefore, it is necessary to systematically investigate these AR of various PMN-PT based SCs manufactured by OC BM and CF BM process and poled by ACP and DCP. The purpose of this study is to systematically investigate the different crystal growth methods, compositions, and poling methods of (PIN)-PMN-PT SCs and to compare with several type of PZT ceramics (ε33/ε0 > 2000) which have already been widely used in medical echo application.