@article{yamashita_sun_xiang_maiwa_lee_kim_jiang_2023, title={Enhanced electrical properties by AC poling of relaxor-Pb(Zr,Ti)O-3 single crystals manufactured by the solid state crystal growth method}, volume={62}, ISSN={["1347-4065"]}, DOI={10.35848/1347-4065/ace537}, abstractNote={Abstract}, number={SM}, journal={JAPANESE JOURNAL OF APPLIED PHYSICS}, author={Yamashita, Yohachi John and Sun, Haiyang and Xiang, Yu and Maiwa, Hiroshi and Lee, Ho-Yong and Kim, Hwang-Pill and Jiang, Xiaoning}, year={2023}, month={Nov} }
 @article{xiang_sun_yamashita_karaki_maiwa_2023, title={Macro- and microstructure of lead perovskite ternary piezoelectric single crystals after direct current and alternating current poling}, volume={131}, ISSN={["1348-6535"]}, DOI={10.2109/jcersj2.22169}, abstractNote={Piezoelectric single crystal (SC) plates of ternary system 0.24Pb(In1/2Nb1/2)O3-0.46Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 manufactured by the continuous-feeding Bridgman method with excellent uniformity were subjected to direct current poling (DCP) and alternating current poling (ACP) processes. And the relationship between their piezoelectric properties and microstructures was investigated using a scanning electron microscope. The dielectric constant (ε33T/ε0) and piezoelectric constant (d33) of the DCP SC were 5500 and 1800 pC/N, respectively, while the microstructure was a uniform random domain structure. Under optimum ACP conditions, the SC had ε33T/ε0 of 7500 and d33 of 2300 pC/N. Four types of 109° domains with stripes ranging from 1 to 3 µm were observed. The under-poled SC had ε33T/ε0 of 1700–6000 and, d33 of 600–2000 pC/N, and a large abnormal microstructure of approximately 25 × 150 µm2 was observed along with 109° stripe-like fine domains. Also, in all SC samples, unclear microstructure layers of approximately 20 µm were observed in the area directly below the top and bottom electrodes. These results indicate that the microstructure of piezoelectric SC is non-uniform between small areas (less than 20 µm2 in a plate), and that precision is essential when discussing the correlation between piezoelectric properties and the microstructure of SCs.}, number={7}, journal={JOURNAL OF THE CERAMIC SOCIETY OF JAPAN}, author={Xiang, Yu and Sun, Yiqin and Yamashita, Yohachi and Karaki, Tomoaki and Maiwa, Hiroshi}, year={2023}, month={Jul}, pages={263–269} }
 @article{xiang_sun_yamashita_karaki_maiwa_2023, title={Microstructure observation of Pb(Mg<sub>1/3</sub>Nb<sub>2/3</sub>)O<sub>3</sub>-PbTiO<sub>3</sub> single crystals by scanning electron microscopy}, volume={62}, ISSN={["1347-4065"]}, DOI={10.35848/1347-4065/acf476}, abstractNote={Abstract}, number={SM}, journal={JAPANESE JOURNAL OF APPLIED PHYSICS}, author={Xiang, Yu and Sun, Yiqin and Yamashita, Yohachi and Karaki, Tomoaki and Maiwa, Hiroshi}, year={2023}, month={Nov} }
 @article{kim_wan_lee_yamashita_jo_jiang_2023, title={Thermal stability studies of alternating current poled Pb(Mg1/3Nb2/3)O-3-PbTiO3 single crystals grown by solid-state crystal growth}, volume={11}, ISSN={["2166-3831"]}, DOI={10.1080/21663831.2022.2161841}, abstractNote={Thermal stabilities of relaxor-PbTiO3 single crystals are of great importance due to their limited operational temperatures in devices. Herein, to elucidate how poling conditions influence thermal stabilities, we investigated direct current (DC) and alternating current (AC) poled Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 (PMN-29PT) crystals grown by solid-state crystal growth, which guarantees more compositional uniformity. Our experiments show that the dielectric permittivity of the DC and AC poled crystals are 3560 and 4970, respectively, after annealing at 99.6°C, implying AC-poling prevails in enhancing thermal stabilities of relaxor-PbTiO3 single crystals. The mechanism behind the dissimilar thermal stabilities can be attributed to different domain configurations. GRAPHICAL ABSTRACT IMPACT STATEMENT Alternating-current poling is of useful for not only enhancing piezoelectric and dielectric properties but also improving the thermal stabilities of relaxor-PbTiO3 single crystals.}, number={5}, journal={MATERIALS RESEARCH LETTERS}, author={Kim, Hwang-Pill and Wan, Haotian and Lee, Ho-Yong and Yamashita, Yohachi and Jo, Wook and Jiang, Xiaoning}, year={2023}, month={May}, pages={383–390} }
 @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(Mg1/3Nb2/3)O3-0.26PbTiO3 (PMN-0.26PT) single crystals. Our experimental results showed that the property enhancement from the ACP was remarkable only when the poling cycle number (NL) 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 NL 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} }
 @misc{yamashita_karaki_lee_wan_kim_jiang_2022, title={A Review of Lead Perovskite Piezoelectric Single Crystals and Their Medical Transducers Application}, volume={69}, ISSN={["1525-8955"]}, DOI={10.1109/TUFFC.2022.3160526}, abstractNote={Piezoelectric materials have been developed since early 1900s and many research had been conducted on the composition and process to obtain higher piezoelectric constants (<inline-formula> <tex-math notation="LaTeX">${d}_{33}$ </tex-math></inline-formula>). Within composition research, lead perovskite relaxor piezoelectric single crystals (SCs) of Pb(Mg1/3Nb2/3)O3–lead titanate PbTiO3 type have been actively studied since 1990s because of their outstanding <inline-formula> <tex-math notation="LaTeX">${d}_{33} >1500$ </tex-math></inline-formula> pC/N compared with those of the conventional Pb(Zr,Ti)O3 ceramics. A major driving force of these SC research has been promoted by mass production of ultrasound transducers and array probes for medical diagnostic systems since early 2000s. However, higher <inline-formula> <tex-math notation="LaTeX">${d}_{33}$ </tex-math></inline-formula> material and process research for these ultrasound devices are almost saturated. In this review article, we present a brief overview of the history, current situation, and future perspective of piezoelectric SCs. The authors believe that the main research in the next century is high <inline-formula> <tex-math notation="LaTeX">${d}_{33}$ </tex-math></inline-formula> SCs with a high composition uniformity and low-energy SC growth methods, such as solid-state SC growth, low-loss SC transducer manufacturing technique, and improved poling process. This is a big technical challenge for all the scientists; however, the relatively large market of medical ultrasound has been expanded year by year, and we hope that the community is motivated to solve such technical problems in the near future.}, number={11}, journal={IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL}, author={Yamashita, Yohachi and Karaki, Tomoaki and Lee, Ho-Yong and Wan, Haotian and Kim, Hwang-Pill and Jiang, Xiaoning}, year={2022}, month={Nov}, pages={3048–3056} }
 @article{wang_yamashita_luo_sun_karaki_fujii_2022, title={Aging rate of dielectric permittivity and loss for PMN-PT based single crystals manufactured by continuous-feeding Bridgman with alternating current poling}, volume={130}, ISSN={["1348-6535"]}, DOI={10.2109/jcersj2.22045}, abstractNote={Aging rate (AR) of dielectric permittivity ( ¾ 33T / ¾ 0 ) of ternary Pb(In 1 / 2 Nb 1 / 2 )O 3 ­ Pb(Mg 1 / 3 Nb 2 / 3 )O 3 ­ x PbTiO 3 (PIN ­ PMN ­ x PT, x = 26 and 30 mol % ) and binary Pb(Mg 1 / 3 Nb 2 / 3 )O 3 ­ x PbTiO 3 (PMN ­ x PT, x = 30 mol % ) single crystals (SCs) grown by the continuous-feeding Bridgman method (CF-BM) were investigated. The AR of dielectric permittivity was 0.6 ­ 2.0 %/ decade, whereas that of dielectric loss of the SCs was 1 ­ 8 %/ decade. Even though the SC growth methods were di ff erent, the AR of CF-BM PMN ­ 30PT SCs were similar with that of conventional one-charge Bridgman method (OC-BM) SCs. In this work, the AR of the SCs possessing high ¾ 33T / ¾ 0 more than 8000 by alternating current poling (ACP) was 4 to 7 times larger than that of PZT ceramics. It is noted that SCs with higher ¾ 33T / ¾ 0 tend to exhibit higher AR. Given that the SCs were in an unstable state within 10 h after poling, the AR presented in this paper was calculated from 10 to 100 h after poling. We hope this work provides a new insight for evaluating the properties of the SCs and addresses the fact that SCs for piezoelectric devices should be properly selected by considering whether their AR could let them work normally during their entire lifetime.}, number={9}, journal={JOURNAL OF THE CERAMIC SOCIETY OF JAPAN}, author={Wang, Zhuangkai and Yamashita, Yohachi and Luo, Cong and Sun, Yiqin and Karaki, Tomoaki and Fujii, Tadashi}, year={2022}, month={Sep}, pages={794–801} }
 @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> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> W0.10–0.25 mm <inline-formula> <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> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> W24 mm <inline-formula> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> T0.48 mm) exhibited ultrahigh dielectric permittivity (<inline-formula> <tex-math notation="LaTeX">$\varepsilon ^{T}_{33}/\varepsilon _{0}$ </tex-math></inline-formula>) and piezoelectric coefficient (<inline-formula> <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> <tex-math notation="LaTeX">$\varepsilon ^{T}_{33}/\varepsilon _{0}$ </tex-math></inline-formula> values decreased from the SC plate <inline-formula> <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> <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> <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> <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{sun_ota_kim_fujii_yamashita_karaki_jiang_wang_2022, title={Enhanced piezoelectric and dielectric properties of AC poled sliver-mode Pb(In1/2Nb1/2)O-3-Pb(Mg1/3Nb2/3)O-3-PbTiO3 single crystals for ultrasonic abdomen probes}, volume={61}, ISSN={["1347-4065"]}, DOI={10.35848/1347-4065/ac8142}, abstractNote={Abstract}, number={SN}, journal={JAPANESE JOURNAL OF APPLIED PHYSICS}, author={Sun, Yiqin and Ota, Yuhei and Kim, Hwang-Pill and Fujii, Tadashi and Yamashita, Yohachi and Karaki, Tomoaki and Jiang, Xiaoning and Wang, Zhuangkai}, year={2022}, month={Nov} }
 @article{luo_karaki_wang_sun_yamashita_xu_2022, title={High piezoelectricity after field cooling AC poling in temperature stable ternary single crystals manufactured by continuous-feeding Bridgman method}, volume={11}, ISSN={["2227-8508"]}, DOI={10.1007/s40145-021-0490-1}, abstractNote={Abstract}, number={1}, journal={JOURNAL OF ADVANCED CERAMICS}, author={Luo, Cong and Karaki, Tomoaki and Wang, Zhuangkai and Sun, Yiqin and Yamashita, Yohachi and Xu, Jiayue}, year={2022}, month={Jan}, pages={57–65} }
 @article{wang_yamashita_sun_fujii_karaki_2022, title={Improvement of piezoelectric properties of relaxor type 0.695Pb(Mg1/3Nb2/3)O-3-0.305 PbTiO3 single crystal plate and silver vibrator by alternating current poling}, volume={61}, ISSN={["1347-4065"]}, DOI={10.35848/1347-4065/ac7c52}, abstractNote={Abstract}, number={SN}, journal={JAPANESE JOURNAL OF APPLIED PHYSICS}, author={Wang, Zhuangkai and Yamashita, Yohachi and Sun, Yiqin and Fujii, Tadashi and Karaki, Tomoaki}, year={2022}, month={Nov} }
 @misc{sun_karaki_yamashita_2022, title={Recent progress on AC poling of relaxor-PbTiO3 ferroelectric single crystals: a review}, volume={61}, ISSN={["1347-4065"]}, DOI={10.35848/1347-4065/ac3a90}, abstractNote={Abstract}, number={SB}, journal={JAPANESE JOURNAL OF APPLIED PHYSICS}, author={Sun, Yiqin and Karaki, Tomoaki and Yamashita, Yohachi}, year={2022}, month={Feb} }
 @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(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (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-PbTiO3 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{sun_karaki_fujii_yamashita_2022, title={Spurious-mode vibrations caused by alternating current poling and their solution process for Pb(Mg1/3Nb2/3)O-3-PbTiO3 single crystals}, volume={8}, ISSN={["2352-8478"]}, DOI={10.1016/j.jmat.2021.05.002}, abstractNote={The effects of alternating current poling (ACP) at 80 °C on electrical properties of [001]-oriented 0.72 Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 (PMN-28PT) single crystals (SCs) have been investigated. The square-wave ACP SCs poled at high voltage (HV, 5 kVrms/cm) occasionally showed large fluctuations and low opposite values of piezoelectric coefficient (d33 = ± 1370 pC/N) in one plate. This revealed spurious-mode vibrations (SMV) of impedance spectrum. However, after depolarizing and repolarizing the sample with a sine-wave ACP at low voltage (LV, 3.5 kVrms/cm), the d33 enhanced to be 1720 pC/N (+26%) and did not exhibit large fluctuation or opposite values in one plate any more. The impedance spectrum became clean and the abnormal SMV disappeared. We proposed four possible mechanisms of the SMV, and speculate that the main cause maybe by macro-scale sub-domain structure and/or phase change in the main domain structure and/or phase in the SC plate due to the specific poling conditions not eternal mechanical damage of PMN-PT SCs. This study will be useful to realize a high d33 and improve other properties of PMN-PT ACP SC ultrasonic transducers without any SMV for high-frequency medical imaging equipment.}, number={1}, journal={JOURNAL OF MATERIOMICS}, author={Sun, Yiqin and Karaki, Tomoaki and Fujii, Tadashi and Yamashita, Yohachi John}, year={2022}, month={Jan}, pages={96–103} }
 @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{sun_karaki_wang_fujii_yamashita_2021, title={Dielectric, piezoelectric, and spurious mode vibration properties by four types of waveforms AC poling for Pb(Mg1/3Nb2/3)O-3-PbTiO3 single crystals}, volume={60}, ISSN={["1347-4065"]}, DOI={10.35848/1347-4065/ac127b}, abstractNote={Four types of waveforms of AC poling (ACP) and DC poling (DCP) were applied on [001]-oriented 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 (PMN-28PT) ferroelectric single crystals (SCs) at 80 °C. High voltage (5 kV cm−1) ACP of all four waveforms and DCP SCs tend to show low piezoelectric coefficient (d 33) less than 1660 pC/N and large spurious-mode vibration (SMV) at the thickness mode vibration (TMV) on impedance spectrum. The highest d 33 of 1830 pC/N was obtained by a triangle wave of 3 kV cm−1 SCs with tiny SMV. By contrast, low voltage (1.5 kV cm−1) ACP SCs with sine and triangle waveforms showed high d 33 of 1750 pC/N and 1670 pC/N without any SMV. We consider that the SMV is more easily caused by the over-poling of PMN-28PT SC. This information will help realize high piezoelectric properties and high production yield for ACP PMN-PT SC transducers for high-resolution medical ultrasound imaging equipment.}, number={SF}, journal={JAPANESE JOURNAL OF APPLIED PHYSICS}, author={Sun, Yiqin and Karaki, Tomoaki and Wang, Zhuangkai and Fujii, Tadashi and Yamashita, Yohachi}, year={2021}, month={Nov} }
 @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{luo_karaki_yamashita_xu_2021, title={High temperature and low voltage AC poling for 0.24Pb(In1/2Nb1/2)O-3- 0.46Pb(Mg1/3Nb2/3)O-3-0.30PbTiO(3) piezoelectric single crystals manufactured by continuous-feeding Bridgman method}, volume={7}, ISSN={["2352-8478"]}, DOI={10.1016/j.jmat.2020.11.003}, abstractNote={Alternating current poling (ACP) in air by changing poling temperature (70–130 °C) and voltages (2–6 kVrms/cm) on pseudo-ternary 0.24 Pb(In1/2Nb1/2)O3-0.46 Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 (PIMN-0.30PT) single crystals (SCs) manufactured by continuous-feeding Bridgman (CF BM) method was investigated. Free dielectric permittivity (εT33/ε0) and piezoelectric constant (d33) were improved to be 7000 and 2340 pC/N, which were 29% higher than those of direct current poling (DCP) at 90 °C with 4 kV/cm (εT33/ε0 = 5440, d33 = 1810 pC/N). However, phase change temperature (Tpc) decreased from 94 °C to 78 °C as opposite results reported by other groups. We demonstrated that the high temperature (HT) ACP improved piezoelectric performance of CF BM SCs, however, the Tpc were different from other crystal growth method. The well-designed ACP process was a promising method for mass production not only to enhance the electrical properties for the pseudo-ternary SCs but also reduce the risk of breakdown and realizes organic solvent-free poling process.}, number={3}, journal={JOURNAL OF MATERIOMICS}, author={Luo, Cong and Karaki, Tomoaki and Yamashita, Yohachi and Xu, Jiayue}, year={2021}, month={May}, pages={621–628} }
 @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-PbTiO3 Single crystals including Pb(Mg1/3Nb2/3)O3-xPbTiO3 (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{sun_karaki_fujii_yamashita_2019, title={Alternate current poling and direct current poling for Pb(Mg1/3Nb2/3)O-3-PbTiO3 single crystals}, volume={58}, ISSN={["1347-4065"]}, DOI={10.7567/1347-4065/ab389c}, abstractNote={We have investigated the effects of alternate current poling (ACP) for four different plates of [100]-oriented (100 – x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN–xPT, x = 28, 29, 30, 31) single crystals (SCs) obtained from one ingot. A record high piezoelectric coefficient d33 of 3000 pC N–1 for PMN–30PT SCs, and a high free dielectric permittivity of 8900 for PMN–28PT SCs by ACP, 27% higher than those of conventional direct current poling (DCP), were confirmed. X-ray analysis revealed a higher (004) peak intensity and angle of ACP SCs compared to those of DCP. We assume that ACP creates a monoclinic multiphase (MB and MC) and eliminates some portion of the tetragonal phase in SCs. In addition, (004) peak shifts were different between the different PT composition SC samples. This work demonstrates an ACP process with excellent cost performance can offer promising prospects and practical value for PMN–xPT SC piezoelectric transducers.}, journal={JAPANESE JOURNAL OF APPLIED PHYSICS}, author={Sun, Yiqin and Karaki, Tomoaki and Fujii, Tadashi and Yamashita, Yohachi}, year={2019}, month={Nov} }
 @article{he_karaki_yang_yamashita_sun_long_2019, title={Dielectric and piezoelectric properties of Pb[(Mg1/3Nb2/3)(0.52)(Yb1/2Nb1/2)(0.15)Ti-0.33]O-3 single-crystal rectangular plate and beam mode transducers poled by alternate current poling}, volume={58}, ISSN={["1347-4065"]}, DOI={10.7567/1347-4065/ab37b7}, abstractNote={The dielectric, piezoelectric and physical properties of the [001]-oriented rectangular plate and beam mode of Pb[(Mg1/3Nb2/3)0.52(Yb1/2Nb1/2)0.15Ti0.33]O3 (PMN-PYbN-PT) ternary single crystals (SC) poled by alternate current poling (ACP) were investigated. The dielectric permittivity ε 33 T / ε 0 and average piezoelectric coefficient d33 were 6800 and 2490 pC/N, respectively, for the rectangular plate sample after ACP, which were 31% and 41% larger than those of the same sample after conventional direct current poling. The highest value of d33 reached 2750 pC N−1. The dielectric loss was reduced by 31%; nevertheless, the d33 improved after ACP. The beam mode electromechanical coupling factor ( k 33 ′ ) was 91% by using ACP, showing the highest value among all relaxor-PT SC systems reported so far. The regular periodic stripe domains were observed in ACP samples, showing high domain wall density and uniform domain size. This work demonstrates that the high performance after ACP is an effective method of improving the relaxor-PT SC transducers.}, journal={JAPANESE JOURNAL OF APPLIED PHYSICS}, author={He, Chao and Karaki, Tomoaki and Yang, Xiaoming and Yamashita, Yohachi and Sun, Yiqin and Long, Xifa}, 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}, 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 (εT33/ε0) 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, εT33/ε0, 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}, abstractNote={First Page}, 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 (εT33/ε0 ∼ 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 εT33/ε0, respectively. Meanwhile, d33 and εT33/ε0 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} }
 @article{chang_chung_luo_kim_yamashita_jones_jiang_2018, title={Dielectric and piezoelectric properties of 0.7 Pb(Mg1/3Nb2/3)O-3-0.3 PbTiO3 single crystal poled using alternating current}, volume={6}, ISSN={["2166-3831"]}, DOI={10.1080/21663831.2018.1498812}, abstractNote={ABSTRACT In this paper, 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-30%PT) single crystal samples were poled using an alternating current (electric field) poling (ACP) method. Compared to the traditional poling method, the piezoelectric coefficient, free and clamped dielectric constants were improved more than 21%. X-ray diffraction result suggests the existence of monoclinic phase (MA) in ACP samples and piezoresponse force microscopy (PFM) result further depicts the finer engineered domain structures. The ACP sample also showed the unique phase transition sequences during the depoling process. Our work could provide a novel domain engineered method to enhance piezoelectric properties of PMN-PT single crystal. GRAPHICAL ABSTRACT IMPACT STATEMENT Piezoelectric and dielectric properties of relaxor-PT single crystals can be significantly enhanced by employing the new alternating current poling method, attributing to the unique heterogenous domain structure containing unprecedented domain wall density.}, number={10}, journal={MATERIALS RESEARCH LETTERS}, author={Chang, Wei-Yi and Chung, Ching-Chang and Luo, Chengtao and Kim, Taeyang and Yamashita, Yohachi and Jones, Jacob L. and Jiang, Xiaoning}, year={2018}, pages={537–544} }