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With the great success on verifying its effectiveness on relaxor-PbTiO3 (PT) single crystals (SCs), alternating current poling (ACP) has been taking a center as a new domain engineering method in the last few years. Compared with the conventional direct current poling (DCP), ACP enables enhanced piezoelectric and dielectric properties. In this article, research progress in ACP and perspectives are introduced. Initially, optimized conditions of ACP for relaxor-PT SCs and unsolved issues on polycrystalline ceramics and spurious modes are reviewed. Second, the ferroelectric domain size dependence of piezoelectricity associated with ACP is discussed. We hypothesize that a tradeoff between domain and domain wall contributions exists for high piezoelectricity, suggesting an optimum 109° domain wall size, which is presumably dependent on compositions, crystallographic symmetries, and domain configurations. Finally, crystals synthesized by a solid-state crystal growth (SSCG) method are briefly introduced due to their unprecedented piezoelectricity obtained by ACP (${d}_{33} \sim 5500$ pC/N). We hope that this work helps to grasp the current status of ACP and to guide future tasks to be studied. [ABSTRACT FROM AUTHOR]

(1- x)Pb(Mg 1/3 Nb 2/3)O 3 - x PbTiO 3 (PMN-PT) single crystals, especially with compositions near its morphotropic phase boundary (MPB), have been employed for a broad range of applications such as ultrasound transducers, sensors, and actuators. To further enhance the properties of PMN-PT, electrode patterning, as a method of domain engineering, was proved to be an effective approach. In our previous report, a 200 nm grating pattern electrode (Ti/Au–MnO x) (nano-electrode) was prepared on one surface of PMN-PT crystal, exhibiting 30% d 33 enhancement. In this work, the multi-layered domain morphology and the domain engineering from nano-electrode were characterized using piezoresponse force microscopy (PFM). A hypothetical domain engineering model for nano-electrodes is established to explain the experimental results as well as the property enhancement from the nano-electrode. The electrode patterning proves that the nano-scale modification can tune the macro-scale piezoelectric properties of the bulk material. Image, graphical abstract Nano-patterned composite electrode (Nano-electrode) , as a method of domain engineering, exhibits 30% d 33 enhancement on (1- x)Pb(Mg 1/3 Nb 2/3)O 3 - x PbTiO 3 (PMN-PT) single crystal. In this work, the mechanism of the property enhancement is studied through the multi-layered domain morphology by piezoresponse force microscopy (PFM). A hypothetical domain engineering model for nano-electrodes is established in the end. [ABSTRACT FROM AUTHOR]

Sliver-mode 0.73Pb(Mg 1/3 Nb 2/3)O 3 -0.27PbTiO 3 single crystals were poled by the alternating current electric field (ACP) along the [001] direction for low-frequency transducer applications. Under ACP with optimized conditions (2.89 kV rms , 0.1 Hz, 10 cycles), the free dielectric constant (ε T 33 / ε 0) was enhanced from 5300 to 7220 and piezoelectric coefficient (d 33) was improved from 1410 to 1920 pC/N, both are about 36% higher than those under traditional direct current poling. The piezoresponse force microscopy observation and phase-field simulation show the similar domain morphologies evolution. During the ACP process, the domain morphology first changes from '4R' to '2R' configuration, and then the length of the 109° domain wall keeps increasing, which leads to a longer range of ordering and a stable lamellar domain structure in the end. The correlation between the domain morphology and the coercive field is also found in both the experiment and simulation. These findings on the effect and mechanism of ACP will help develop advanced low-frequency single crystal transducer arrays. Evolution of domain structures of rhombohedral PMN-PT during ACP process was studied through the domain morphology tracking, which developed from '4R' to '2R' configuration. The results also show a good correlation between coercive field and domain structure, attributing to a new domain engineering model. [Display omitted] [ABSTRACT FROM AUTHOR]