@article{wan_luo_kim_chung_chang_yamashita_jiang_2022, title={<p>The overpoling effect of alternating current poling on rhombohedral Pb(Mg1/3Nb2/3)O-3-PbTiO3 single crystals</p>}, volume={120}, ISSN={["1077-3118"]}, DOI={10.1063/5.0086057}, abstractNote={The overpoling effect of alternating current poling (ACP) was studied on [001]-orientated rhombohedral Pb(Mg 1/3 Nb 2/3 )O 3 -0.26PbTiO 3 (PMN-0.26PT) single crystals. Our experimental results showed that the property enhancement from the ACP was remarkable only when the poling cycle number ( N L ) was kept low. When ACP was continued after the saturation, dielectric and piezoelectric properties gradually dropped down to traditional direct current poled levels or even lower. Such a decrease in material properties caused by the large N L during ACP was defined as the “overpoling effect of ACP” in this study. The following lattice symmetry and domain structure characterization studies were performed through x-ray diffraction (XRD) and piezoelectric force microscopy (PFM) to find the origin of the overpoling effect. The XRD measurements combined with temperature dependence of dielectric properties demonstrated that the field-induced phase transition continued when the samples became overpoled. Further PFM measurements illustrated that the domain density of the overpoled ACP sample was significantly lower than that of the normal one, while the “2R” domain configuration was maintained through the ACP process. In addition, the hysteresis loop characterization indicated large decreases in the coercive fields. The discovered overpoling effect of ACP could help us understand the mechanisms of ACP and optimize the ACP process.}, number={19}, journal={APPLIED PHYSICS LETTERS}, author={Wan, Haotian and Luo, Chengtao and Kim, Hwang-Pill and Chung, Ching-Chang and Chang, Wei-Yi and Yamashita, Yohachi and Jiang, Xiaoning}, year={2022}, month={May} }
 @article{sun_ota_fujii_yamashita_kim_wan_jiang_karaki_2022, title={Enhanced Properties of 3-MHz Sliver-Mode Vibrators for Cardiac Probes With Alternating Current Poling for Pb(Mg1/3Nb2/3)O-3-PbTiO3 Single Crystals}, volume={69}, ISSN={["1525-8955"]}, DOI={10.1109/TUFFC.2022.3199741}, abstractNote={We investigated the effects of alternating current poling (ACP) on the piezoelectric and dielectric properties of 3-MHz sliver mode (L13 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> W0.10–0.25 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> T0.48 mm) vibrators fashioned from Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 (PMN-0.30PT) single crystal (SC) plate manufactured using the continuous-feeding Bridgman (CF-BM) method for cardiac probes. The ACP SC plate (L13 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> W24 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> T0.48 mm) exhibited ultrahigh dielectric permittivity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon ^{T}_{33}/\varepsilon _{0}$ </tex-math></inline-formula> ) and piezoelectric coefficient ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${d}_{33}$ </tex-math></inline-formula> ) of 9690 and 2920 pC/N, respectively. After array dicing, the SC slivers with widths of 0.10, 0.15, 0.20, and 0.25 mm were obtained, and their average <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon ^{T}_{33}/\varepsilon _{0}$ </tex-math></inline-formula> values decreased from the SC plate <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon ^{T}_{33}/\varepsilon _{0}$ </tex-math></inline-formula> by 45% (5330), 29% (6880), 19% (7840), and 15% (8240), respectively, possibly because of heat and mechanical damage during the dicing. A combination of the ACP and a postdicing direct current poling (ACP-DCP) recovered their <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon ^{T}_{33}/\varepsilon _{0}$ </tex-math></inline-formula> values to 6050, 7080, 8140, and 8540, respectively. The sliver mode electromechanical coupling factors ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}'_{33}$ </tex-math></inline-formula> ) were confirmed to exceed 93% after the ACP-DCP process, which were more than 4% higher than those of DCP-DCP SC slivers. The measured impedance spectra indicated that the SC slivers with 0.10–0.20 mm in width showed no spurious mode vibration near the fundamental <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}'_{33}$ </tex-math></inline-formula> mode. We conclude that the ACP-DCP SC slivers maintained more enhanced piezoelectric and dielectric properties than the DCP-DCP samples. These results will have important implications for the commercial application of ACP technology to medical imaging ultrasound probes.}, number={11}, journal={IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL}, author={Sun, Yiqin and Ota, Yuhei and Fujii, Tadashi and Yamashita, Yohachi and Kim, Hwang-Pill and Wan, Haotian and Jiang, Xiaoning and Karaki, Tomoaki}, year={2022}, month={Nov}, pages={3087–3094} }
 @article{kim_wan_lu_yamashita_jiang_2022, title={Scaling effects in the alternating-current poling of thin PIN-PMN-PT single crystals}, volume={120}, ISSN={["1077-3118"]}, DOI={10.1063/5.0084994}, abstractNote={AC-poling of Pb(In 1/2 Nb 1/2 )O 3 -Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 (PIN-PMN-PT) single crystals with a thickness of 0.06–0.16 mm was studied in this paper. Compared with DC-poled samples, enhancements in piezoelectric and dielectric properties can be obtained when the thickness is above 0.1 mm. However, inconsistency in poling effects was found in the crystals with thickness below 0.1 mm. To elucidate why such scaling effect arises, surface roughness was measured by an atomic force microscopy to correlate surface morphology and poling effects. It was found that non-uniform surface roughness led to inconsistent and decreased properties. Furthermore, temperature-dependent dielectric permittivity spectra were measured to explore how crystal thickness affects the thermal stability of ferroelectric phases. It is noted that complex changes in crystallographic symmetries emanate by decreasing thickness. Such phenomena can be attributed to more influential effects of surface morphology when thickness is reduced. We hope this work suggests a clue for solving the scaling effects of AC-poling on relaxor-PbTiO 3 single crystals.}, number={14}, journal={APPLIED PHYSICS LETTERS}, author={Kim, Hwang-Pill and Wan, Haotian and Lu, Xuanming and Yamashita, Yohachi and Jiang, Xiaoning}, year={2022}, month={Apr} }
 @article{wan_luo_liu_chang_yamashita_jiang_2021, title={Alternating current poling on sliver-mode rhombohedral Pb(Mg1/3Nb2/3)O-3-PbTiO3 single crystals}, volume={208}, ISSN={["1873-2453"]}, DOI={10.1016/j.actamat.2021.116759}, abstractNote={Sliver-mode 0.73Pb(Mg1/3Nb2/3)O3-0.27PbTiO3 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 kVrms, 0.1 Hz, 10 cycles), the free dielectric constant (εT33/ε0) was enhanced from 5300 to 7220 and piezoelectric coefficient (d33) 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.}, journal={ACTA MATERIALIA}, author={Wan, Haotian and Luo, Chengtao and Liu, Chang and Chang, Wei-Yi and Yamashita, Yohachi and Jiang, Xiaoning}, year={2021}, month={Apr} }
 @article{wan_luo_chung_yamashita_jiang_2021, title={Enhanced dielectric and piezoelectric properties of manganese-doped Pb(In1/2Nb1/2)O-3-Pb(Mg1/3Nb2/3)O-3-PbTiO3 single crystals by alternating current poling}, volume={118}, ISSN={["1077-3118"]}, DOI={10.1063/5.0038207}, abstractNote={Alternating current poling (ACP) was performed on Gen III relaxor-PT Mn-doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (Mn: PIN-PMN-PT) single crystals with the poling direction of [001]. Experimental results proved that ACP could bring property enhancement to both k31 and k33 mode crystals. Compared to those from traditional direct current poling (DCP), ACP with the optimized conditions (20 kV/cm, 0.1 Hz, and 20 cycles) enhanced the dielectric and piezoelectric properties of k31-mode mode crystals by more than 30%, where the enhanced free dielectric constant and piezoelectric coefficient d33 reached 5300 and 1750 pC/N, respectively. Furthermore, replacing DCP with ACP could increase the advantages of Gen III relaxor-PT. The coupling factors k31 and k33 were enhanced to 0.472 and 0.915, the mechanical quality factor Qm was enhanced by 17%, and the depoling temperature was raised by 17 °C to 123 °C. In the following mechanism study, in situ x-ray diffraction (XRD) combined with the temperature-dependent dielectric constant measurement proved the introduction of the monoclinic phases after ACP, while piezoresponse force microscopy (PFM) observation showed “2R”-like “2M” domain morphologies in ACP single crystals. Both these intrinsic and extrinsic factors are believed to be the keys to the mechanisms of property enhancement behind ACP. This study proved that ACP is an effective property enhancement method suitable for Gen III relaxor-PT single crystals and will promote its applications in high-temperature and high-power devices.}, number={10}, journal={APPLIED PHYSICS LETTERS}, author={Wan, Haotian and Luo, Chengtao and Chung, Ching-Chang and Yamashita, Yohachi and Jiang, Xiaoning}, year={2021}, month={Mar} }
 @article{wan_yamashita_jiang_2021, title={Observation of the Domain Morphology of Pb(Mg1/3Nb2/3)O-3-xPbTiO(3) Single Crystals}, ISSN={["2378-377X"]}, DOI={10.1109/NMDC50713.2021.9677513}, abstractNote={Relaxor-PbTiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Single crystals including Pb(Mg <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/3</inf> Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2/3</inf> )O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> -xPbTiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> (PMN-xPT) have been widely used and extensively studied in the last two decades due to their ultrahigh piezoelectric properties for acoustic devices. However, the piezoelectric properties of PMN-xPT single crystals are highly dependent on the PT contents. In this work, the domain morphologies of PMN-xPT with different PT compositions (x = 0.26 and 0.28, rhombohedral phase) after direct current poling (DCP) were observed by piezoresponse force microscopy (PFM). The domain morphologies and the domain wall densities were compared to study the influences of the PT compositions on the piezoelectric properties of PMN-xPT. The PFM images showed that after DCP, PMN-xPT single crystals of two different compositions all had the domain morphologies with ‘4R’ configuration in which both 109° and 71° domain walls could be clearly identified. Compared with PMN-0.26PT, PMN-0.28PT single crystals had similar 109° domain wall densities (Domain width: 1012 nm vs 1025 nm) but higher 71° domain wall densities (Domain width: 426 nm vs 645 nm). The higher piezoelectric properties of PMN-xPT single crystals were found to correlate with the higher 71° domain wall densities.}, journal={2021 IEEE 16TH NANOTECHNOLOGY MATERIALS AND DEVICES CONFERENCE (NMDC 2021)}, author={Wan, Haotian and Yamashita, Yohachi and Jiang, Xiaoning}, year={2021} }
 @article{luo_wan_chang_yamashita_paterson_jones_jiang_2019, title={Effect of low-frequency alternating current poling on 5-mm-thick 0.7Pb(Mg1/3Nb2/3)O-3-0.3PbTiO(3) single crystals}, volume={115}, ISSN={["1077-3118"]}, DOI={10.1063/1.5127292}, abstractNote={Alternating current (electric field) poling (ACP) was applied on [001]-oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-0.3PT) single crystal samples with dimensions of 5 × 1.25 × 1.25 mm3 (with electrodes on the 1.25 × 1.25 mm2 surfaces), and the influence of ACP frequency (fACP) was studied. Compared to those from traditional direct (electric field) poling samples, the piezoelectric coefficient (d33) and free dielectric constant (eT33/e0) of ACP samples could gain up to a 67% increase to 3200 pC/N and 10 500, respectively. The influence of fACP was studied on two main aspects: saturated properties and dynamic saturation process. In general, ACP samples with lower fACP had higher saturated d33, eT33/e0, and coupling factor k33, as well as lower dielectric loss and faster saturation speed. The ACP dynamics during the saturation process were studied by measuring the polarization-vs-electric field hysteresis loops (P-E loops). The P-E loops illustrated that the coercive field of ACP samples could be further tuned from 1.84 kV/cm to 3.03 kV/cm by changing fACP (0.1–10 Hz). This work demonstrated the enormous potential of ACP optimization in relaxor-PT single crystal-based low-frequency transducer applications.}, number={19}, journal={APPLIED PHYSICS LETTERS}, author={Luo, Chengtao and Wan, Haotian and Chang, Wei-Yi and Yamashita, Yohachi and Paterson, Alisa R. and Jones, Jacob and Jiang, Xiaoning}, year={2019}, month={Nov} }
 @article{luo_wan_chang_yamashita_paterson_jones_jiang_2019, title={Effect of low-frequency alternating current poling on 5-mm-thick 0.7Pb(Mg1/3Nb2/3)O-3-0.3PbTiO(3) single crystals (vol 115, 192904, 2019)}, volume={115}, ISSN={["1077-3118"]}, DOI={10.1063/1.5139662}, number={26}, journal={APPLIED PHYSICS LETTERS}, author={Luo, Chengtao and Wan, Haotian and Chang, Wei-Yi and Yamashita, Yohachi and Paterson, Alisa R. and Jones, Jacob and Jiang, Xiaoning}, year={2019}, month={Dec} }
 @article{wan_luo_chang_yamashita_jiang_2019, title={Effect of poling temperature on piezoelectric and dielectric properties of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 single crystals under alternating current poling}, volume={114}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.5094362}, DOI={10.1063/1.5094362}, abstractNote={In this work, the piezoelectric and dielectric properties of [001]-oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 single crystals under alternating current poling (ACP) at different temperatures were studied. The piezoelectric coefficients (d33 ∼ 1930 pC/N, d31 ∼ −850 pC/N) and free dielectric permittivity (eT33/e0 ∼ 7570) reached their highest values when the poling temperature (Tpoling) was 70 °C. Compared with traditional direct current electric field poling at 20 °C, 70 °C-ACP samples showed an enhancement of 40%, 35%, and 49% for d33, d31, and eT33/e0, respectively. Meanwhile, d33 and eT33/e0 were enhanced by about 9% when Tpoling increased from 20 °C to 70 °C under ACP, while d31 remained the same value and the dielectric loss was lowered from 0.29% to 0.22%. Moreover, ACP samples with different Tpoling have similar electromechanical coupling factors (k31 ∼ 0.44, kt ∼ 0.60). A discussion of the mechanism for the ACP enhancement was based on the domain observation using piezoresponse force microscopy, and the results showed that the domain densities of ACP samples with different Tpoling were positively correlated with their piezoelectric properties. This work demonstrated the enormous potential of ACP optimization for relaxor-PT single crystal applications.}, number={17}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Wan, Haotian and Luo, Chengtao and Chang, Wei-Yi and Yamashita, Yohachi and Jiang, Xiaoning}, year={2019}, month={Apr}, pages={172901} }