@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} }
 @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{xiao_luo_huangfu_guo_2020, title={Boosting the Photocatalytic Ability of Bandgap Engineered (Na0.5Bi0.5)TiO3-BaTiO3 by N-Ni Codoping}, volume={124}, ISSN={["1932-7455"]}, DOI={10.1021/acs.jpcc.0c02542}, abstractNote={Bandgap engineered ferroelectrics have raised the utmost interest in achieving visible/near-infrared light utilization. The gap states in ferroelectrics can not only realize the absorption of visible/near-infrared light but also keep their excellent piezoelectricity. However, the impurity energy levels provide limited photogenerated carrier, and the doping ions may act as trapping sites, which make it difficult to convert enough sunlight to chemical or electrical energy. In this work, we report a novel strategy to achieve the cooperative interaction of codopants and significantly enhance the photocatalytic activity of the host ferroelectrics. The (N3–, Ni2+)-codoped (Na0.5Bi0.5)TiO3–BaTiO3 composition was taken as the concrete example, which has a lower bandgap of 2.06 eV without gap state. Largely enhanced photocatalytic activity including organic pollutant degradation and photocatalytic oxidative desulfurization were realized, in which the photodegradation efficiency of RhB was increased by 250% and dibenzothiophene could be degraded to lower than 10 ppm within 150 min. Moreover, a long-standing confusion about the appearance/disappearance of bandgap state in transition-metal-doped ferroelectrics has been properly clarified based on theoretical calculation result. Our work could provide a new insight for advancing the bandgap engineering and improving the energy conversion efficiency.}, number={22}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Xiao, Hongyuan and Luo, Chengtao and Huangfu, Geng and Guo, Yiping}, year={2020}, month={Jun}, pages={11810–11818} }
 @article{luo_chang_gao_chang_li_viehland_tian_jiang_2020, title={Multi-layered domain morphology in relaxor single crystals with nano-patterned composite electrode}, volume={182}, ISSN={["1873-2453"]}, DOI={10.1016/j.actamat.2019.10.017}, abstractNote={(1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (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–MnOx) (nano-electrode) was prepared on one surface of PMN-PT crystal, exhibiting 30% d33 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.}, journal={ACTA MATERIALIA}, author={Luo, Chengtao and Chang, Wei-Yi and Gao, Min and Chang, Chih-Hao and Li, Jiefang and Viehland, Dwight and Tian, Jian and Jiang, Xiaoning}, year={2020}, month={Jan}, pages={10–17} }
 @article{gao_luo_chang_leung_tian_li_jiang_viehland_2019, title={Apparent phase stability and domain distribution of PMN-30PT single crystals with nanograted Au/MnOx electrodes}, volume={169}, ISSN={["1873-2453"]}, DOI={10.1016/j.actamat.2019.02.039}, abstractNote={X-ray diffraction (XRD) reciprocal space mapping (RSM) was used to investigate how nanograted electrodes affect the nanodomain distribution and average crystal structure in near-surface regions of poled Pb(Mg1/3Nb2/3)O3-30%PbTiO3 (PMN-30PT) single crystals. The RSM scans revealed a transverse broadening along the (H00) direction, which was quite different from that of either the rhombohedral (R) or monoclinic A (MA) phase. This broadening provides evidence of a non-uniform distribution of tilt angles between neighboring nanodomains, induced by a gradient in the applied electric field (E). Investigations of the front and back surfaces of the crystals revealed significant differences in the RSM scans. Gradients in the domain distribution and apparent symmetry may extend throughout the crystal thickness. The data evidence changes in the nanodomain distribution that results in adaptations of the average symmetry.}, journal={ACTA MATERIALIA}, author={Gao, Min and Luo, Chengtao and Chang, Wei-Yi and Leung, Chung Ming and Tian, Jian and Li, Jiefang and Jiang, Xiaoning and Viehland, D.}, year={2019}, month={May}, pages={28–35} }
 @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={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.}, 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} }