Advantages and challenges of relaxor-PbTiO3 ferroelectric crystals for electroacoustic transducers – A review

Abstract

Relaxor-PbTiO3 (PT) based ferroelectric crystals with the perovskite structure have been investigated over the last few decades due to their ultrahigh piezoelectric coefficients (d33 > 1500 pC/N) and electromechanical coupling factors (k33 > 90%), far outperforming state-of-the-art ferroelectric polycrystalline Pb(Zr,Ti)O3 ceramics, and are at the forefront of advanced electroacoustic applications. In this review, the performance merits of relaxor-PT crystals in various electroacoustic devices are presented from a piezoelectric material viewpoint. Opportunities come from not only the ultrahigh properties, specifically coupling and piezoelectric coefficients, but through novel vibration modes and crystallographic/domain engineering. Figure of merits (FOMs) of crystals with various compositions and phases were established for various applications, including medical ultrasonic transducers, underwater transducers, acoustic sensors and tweezers. For each device application, recent developments in relaxor-PT ferroelectric crystals were surveyed and compared with state-of-the-art polycrystalline piezoelectrics, with an emphasis on their strong anisotropic features and crystallographic uniqueness, including engineered domain - property relationships. This review starts with an introduction on electroacoustic transducers and the history of piezoelectric materials. The development of the high performance relaxor-PT single crystals, with a focus on their uniqueness in transducer applications, is then discussed. In the third part, various FOMs of piezoelectric materials for a wide range of ultrasound applications, including diagnostic ultrasound, therapeutic ultrasound, underwater acoustic and passive sensors, tactile sensors and acoustic tweezers, are evaluated to provide a thorough understanding of the materials’ behavior under operational conditions. Structure-property-performance relationships are then established. Finally, the impacts and challenges of relaxor-PT crystals are summarized to guide on-going and future research in the development of relaxor-PT crystals for the next generation electroacoustic transducers.

Functional characterization of piezocrystals monitored under high power driving conditions

“…8. The temperature values recorded at depolarization were 100°C and 120°C for PMN-PT and PIN-PMNT-PT respectively, which are lower than the depolarization temperature values of 135°C and 191°C reported in literature [1]. This may be caused by a combination of high temperature and high electric field.…”

“…Relaxor-based ferroelectric single crystal piezoelectric materials ("piezocrystals") have gained huge interest in both academic research and industrial applications [1]. These materials exhibit extraordinary piezoelectric properties, making them suitable for a range of passive and active applications, including in high bandwidth and high sensitivity piezoelectric transducers [2].…”

“…As shown in Fig.1, when a 10 x 10 x 1 mm 3 PMN-PT thickness-extensional (TE) plate is driven at 110 Vpp, the temperature increases to more than 130°C, well beyond TRT = 96°C [1]. Therefore, it is essential to characterize such materials in active configurations, allowing better understanding of property variation and facilitating transducer design in finite element analysis for more demanding high power applications.…”

A Diagram of the Structure Evolution of Pb(Zn1/3Nb2/3) O3-9%PbTiO3 Relaxor Ferroelectric Crystals with Excellent Piezoelectric Properties

“…Recently, Zhang et al and Sun et al [2][3][4] These properties are expected to be applied in high-quality piezoelectric devices, such as medical ultrasonic transducers, actuators, and sonars, as replacements for conventional PZT ceramics [4][5][6][7]. In the PZN-9PT crystal system, different from the normal ferroelectric (e.g., PT) [8] with a long coherent length of order, the random distribution of B-ions (here, B represents Zn, Nb, and Ti atoms) prevents the formation of the long-range ferroelectric order [8,9].…”

A Diagram of Structure Evolution of Pb(Zn_1/3Nb_2/3)O₃-9%PbTiO₃ Relaxor Ferroelectric Crystals with Excellent Piezoelectric Properties

“…Recently, Zhang et al and Sun et al [2][3][4] demonstrated that the Pb(Zn1/3Nb2/3)0.91Ti0.09O3 (PZN-9PT) crystal exhibits an exceptionally large piezoelectric constant (d33 > 2000 pC/N) and electromechanical coupling factor in longitudinal bar mode (k33 > 92%). These properties are expected to be applied in high-quality piezoelectric devices, such as medical ultrasonic transducers, actuators, and sonars, as replacements for conventional PZT ceramics [4][5][6][7].…”