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이병완,고재현,Xiaobing Li,Haosu Luo 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.9
The elastic properties of lead-free (Na1/2Bi1/2)TiO3-BaTiO3 single crystals near the morphotropic phase boundary were investigated by using Brillouin spectroscopy at room temperature. The measured longitudinal elastic constants of unpoled single crystals with a BaTiO3 content of 5% exhibited large changes depending on the scattering geometry, indicating that a substantial acoustic dispersion effect exists in this system. This was attributed to the relaxor nature due to inherent disorder in the A-site of the perovskite structure.
납이 포함되지 않은 압전 특성의 (Na 1/2 Bi 1/2 TiO 3 ) (1-x) -(BaTiO 3 ) x 상전이 거동 연구
이병완(Byoungwan Lee),Haosu Luo,김정규(, Jung Kyu Kim) 한국세라믹학회 2020 세라미스트 Vol.23 No.1
In this study, the phase transition behaviors of lead-free (Na 1/2 Bi 1/2 TiO 3 ) (1-x) -(BaTiO 3 ) x (NBT-BT) are investigated by using Brillouin spectroscopy. The elastic properties, sound velocity and absorption coefficient of NBT-BT are characterized as a function of temperature along different crystallographic axes. The temperature dependences of the elastic constants of NBT-BT near the morphotropic phase boundary are determined for the first time. The unpoled NBT-BT single crystals exhibits the typical relaxor behaviors, presenting broad acoustic and dielectric anomalies. The application of electric field induced discontinuous changes in the elastic properties at ~110℃, which indicates field-induced phase transition occurred. The electric field also changes the dielectric constant from more relaxor-like to ferroelectric-like dielectric behavior.
오수한,고재현,Li Xiaobing,Luo Haosu 한국물리학회 2020 Current Applied Physics Vol.20 No.7
Acoustic anomalies of relaxor ferroelectric Na1/2Bi1/2TiO3 single crystals were investigated over a wide temperature range from −196 °C to 900 °C by using Brillouin spectroscopy. The longitudinal sound velocity, the acoustic absorption coefficient and the elastic constant C11 were determined for the acoustic phonon mode propagating in the [100] direction. Two acoustic anomalies, weaker ones at the cubic-tetragonal phase transition temperature of ~540 °C and more pronounced ones at temperatures near 315 °C near the dielectric maximum temperature, were investigated and discussed in relation with the relevant order parameters coupled to the acoustic waves. The relaxation dynamics in the cubic phase were studied based on the flattening of the mode frequency and the half width, which was observed for the first time, and a modified Arrhenius law.
오수한,이병완,장문규,고재현,Xiaobing Li,Haosu Luo 한국물리학회 2019 Current Applied Physics Vol.19 No.11
The acoustic and vibrational properties of Mn-doped (Na1/2Bi1/2)TiO3-xBaTiO3 with x=0.05 were investigated by using Brillouin and Raman spectroscopies and compared with those of undoped crystals. The mode frequency and the half width of the Brillouin doublet of the longitudinal acoustic mode showed more drastic changes near the dielectric maximum temperature compared to the broad and diffused changes of the undoped crystals, which indicates that Mn-doping induces polar domains larger than the typical polar nanoregions formed in undoped counterpart. The acoustic anomalies were most pronounced along the<100>direction suggesting that the polarization fluctuations are anisotropic and largest along this direction. Temperature dependence of Raman spectra showed that there are two characteristics temperatures where mode splitting occurs due to local symmetry changes. The high-temperature anomaly was associated with the changes in the acoustic properties, while the low-temperature mode splitting was related to the dielectric anomaly near depolarization temperature.
Deng Tingyu,Fang Bijun,Zhu Rongfeng,Chen Jianwei,Luo Haosu 한국물리학회 2021 Current Applied Physics Vol.21 No.-
Due to the good dielectric, piezoelectric and ferroelectric properties, the pseudo-ternary ferroelectric single crystals Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) have been widely concerned and studied. In this study we found that the dynamic hysteresis loop area <A> with electric field E0 and frequency f0 of the 0.16 Pb(In1/2Nb1/2)O3-0.62 Pb(Mg1/3Nb2/3)O3-0.22PbTiO3 (0.16PIN-0.62PMN-0.22 PT) single crystals satisfies the relational equation <A> ∝ E0β f0α . In the <A> ∝ E0β relationship, both linear stages are found correlated with the low electric field in the first stage E0<Ec and the high electric field in the third stage E0 > 3Ec. The hysteresis loop area <A> with frequency f0 relationship satisfies the equation <A> ∝ f0α with roughly linear trend and the hysteresis loop area <A> decreases with increasing frequency f0. Such electric field dependent dynamic hysteresis scaling can be observed by polarized light microscopy.
Renbing Sun,Bijun Fang,Limin Zhou,Qinhui Zhang,Xiangyong Zhao,Haosu Luo 한국물리학회 2011 Current Applied Physics Vol.11 No.1
(1-x)(Ni_0.8Zn_0.1Cu_0.1)Fe_2O_4/x0.58Pb(Ni_1/3Nb_2/3)O_3-0.02Pb(Zn_1/3Nb_2/3)O_3-0.05Pb(Ni_1/2W_1/2)O_3-0.35PbTiO_3((1-x)NZCF/xPNZNWT) magnetoelectric composites were prepared by conventional solidestate reaction method via low-temperature sintering technique. The low-temperature sintering technique can prepare dense composites, where the ferrite and piezoelectric phases coexist in the synthesized particulate composites, and no apparent mutual solubility takes place between the two phases. The (1-x)NZCF/xPNZNWT ceramic composites exhibit excellent integrated electrical properties, where diffused dielectric response peaks, typical P-E hysteresis loops and excellent piezoelectric property can be obtained. The (1-x)NZCF/xPNZNWT composites prepared by the low-temperature sintering process can be electrically and magnetically poled to exhibit apparent magnetoelectric effect, indicating that such technique is convenient to develop excellent particulate magnetoelectric materials in the future.
Wanwan Ji,Shuai Feng,Bijun Fang,Xiangyong Zhao,Shuai Zhang,Jianning Ding,Haosu Luo 한국물리학회 2018 Current Applied Physics Vol.18 No.3
High Curie temperature (TC) xBi(Ni1/2Ti1/2)O3-(1-x)Pb(Zr1/2Ti1/2)O3 (xBNT-(1-x)PZT, BNT-PZT) piezoelectric ceramics were prepared by the conventional ceramic processing. The composition-induced morphotropic phase boundary (MPB) and its influences on structure and electrical performance were investigated. The synthesized BNT-PZT ceramics exhibit rather pure perovskite structure, and densified microstructure morphology with uniform elementals distribution in both grains and grain boundaries. With increasing the content of Bi(Ni1/2Ti1/2)O3 (BNT), crystal structure of the BNT-PZT ceramics transform from tetragonal phase to rhombohedral phase, and dielectric response peaks change from narrow shape to very broad shape but all presenting dielectric frequency dispersion. The diffused and relaxation dielectric behavior can be fitted well by the quadratic law, and the Vogel-Fulcher law fitting provides additional information on the relaxation characteristic. The MPB effects are confirmed further by ferroelectric and piezoelectric properties measurements. High-TC combined with excellent piezoelectric performance can be realized in the BNT-PZT system, which presents promising applications in geothermal exploration, aerospace and related elevated temperatures fields.
Rongfeng Zhu,Qihui Zhang,Bijun Fang,Jianning Ding,Xiangyong Zhao,Haosu Luo 한국물리학회 2016 Current Applied Physics Vol.16 No.12
In situ temperature dependent ferroelectric domains dynamic evolution of the (001)pc oriented 0.91Pb(Zn1/3Nb2/3)O3-0.09PbTiO3 (PZNT91/9) single crystals was observed by polarized light microscopy (PLM) and real time synchrotron-radiation (SR) X-ray white-beam topography. Intricate domain structures including monoclinic phase are distinguished by PLM at room temperature, and irreversible domain configuration dynamic evolution upon thermal cycling is observed by both methods. Such irreversible domain evolution combined with coexistence of multi-phases and polarization rotation may be related to the extraordinary piezoelectric performance in the ferroelectric single crystals with the morphotropic phase boundary (MPB) compositions.
Hang Hai,Jiang Xianyao,Lin Di,Wang Feifei,Wang Xian,Luo Haosu 한국물리학회 2023 Current Applied Physics Vol.47 No.-
Pb(Mg1/3Nb2/3)O3-xPbTiO3 single crystal/epoxy 1–3 piezoelectric composite was designed to decrease acoustic impedance and to improve the electromechanical property, which was vital to the ultrasound transducers. The piezo-/dielectric properties of the PMNT/epoxy 1–3 composites prepared by the different poling methods were measured. It was found that piezoelectric coefficient d33, dielectric constant εT33/ε0, and electromechanical factor kt of composites exhibited the significant increases of 16.41%, 6.89%, and 1.97% under optimized alternating current polarization (ACP), compared with those of the samples using direct current polarization (DCP). The domain patterns suggested that the remarkable regular striped domain and high domain wall density of the ACP sample could result in performance enhancements. The ACP composite-based transducer’s bandwidth (BW) and relative sensitivity (RS) were improved by 6.27% and 1.93 dB. These results indicated that the ACP effectively enhances the piezoelectric composite’s performances, and BW and RS of the transducer based on ACP piezoelectric materials are improved simultaneously.