• Title/Summary/Keyword: ferroelectricity

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Electrical Properties and Phase Transition Behavior of Lead-Free BaTiO3-Modified Bi1/2Na1/2TiO3-SrTiO3 Piezoelectric Ceramics (BaTiO3 첨가에 따른 Bi1/2Na1/2TiO3-SrTiO3 무연 압전 세라믹스의 전기적 특성 및 상전이 거동 연구)

  • Kang, Yubin;Park, Jae Young;Devita, Mukhllishah Aisyah;Duong, Trang An;Ahn, Chang Won;Kim, Byeong Woo;Han, Hyoung-Su;Lee, Jae-Shin
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.35 no.5
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    • pp.516-521
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    • 2022
  • We investigated the microstructure, crystal structure, dielectric, and elecromechanical strain properties of lead-free BaTiO3 (BT)-modified (Bi1/2Na1/2)TiO3-SrTiO3 (BNT-ST) piezoelectric ceramics. Samples were prepared by a conventional ceramic processing route. Temperature dependent dielectric properties confirmed that a phase transition from a nonergodic relaxor to an ergodic relaxor was induced when the BT concentration reached 1.5 mol%, interestingly, where the average grain size reached a maximum value of 4.5 ㎛. At the same time, enhanced electromechanical strain (Smax/Emax = 600 pm/V) was obtained. It is suggested that the induced ferroelectric-relaxor phase transition by the BT modification is responsible for the enhancement of electromechanical strain in 1.5 mol% BT-modified BNT-ST ceramics.

Pyroelectricity of BaTiO3-doped PMNT ferroelectric system for pyroelectric sensor

  • Yeon Jung Kim
    • Journal of the Korean institute of surface engineering
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    • v.56 no.6
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    • pp.380-385
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    • 2023
  • In this study, an MPB PMNT system containing 0.05 to 0.10 wt.% BaTiO3 was synthesized using a traditional chemical method and its pyroelectricity was investigated. Pyroelectricity, dielectricity, and ferroelectricity of the synthesized BaTiO3-PMNT system were analyzed by heat treatment at 1240~1280 ℃ for 4 hours to evaluate its applicability as a pyroelectric sensor. Unlike the simple ABO3 ferroelectric, the BaTiO3-doped PMNT system exhibited phase transition characteristics over a wide temperature range typical of complex perovskite structures. Although no dramatic change could be confirmed depending on the amount of BaTiO3 added, stable pyroelectricity was maintained near room temperature and over a wide temperature range. When the amount of BaTiO3 added increased from 0.05BaTiO3-PMNT to 0.10BaTiO3-PMNT, the electric field slightly increased from 5.00×103 kV/m to 6.75×103 kV/m, and the maximum value of remanent polarization slightly increased from 0.223 C/m2 to 0.234 C/m2. The pyroelectric coefficients of 0.05BaTiO3-PMNT and 0.10BaTiO3- PMNT at room temperature were measured to be ~0.0084 C/m2K and ~0.0043 C/m2K, respectively. The relaxor ferroelectric properties of the BaTiO3-PMNT system were confirmed by analyzing the plot of Kmax/K versus (T-Tmax)γ. The BaTiO3-doped MPB PMNT system showed a distinct pyroelectric performance index at room temperature, and the values were Fv ~ 0.0362 m2/C, Fd ~ 0.575×10-4 Pa-1/2.

Electrical Properties of SrBi$_2$$Nb_2$>$O_9$ Thin Films deposited by RF Magnetron Sputtering Method (RF 마그네트론 스퍼터링법에 의해 증착된 SrBi$_2$$Nb_2$>$O_9$ 박막의 전기적 특성에 관한 연구)

  • Zhao, Jin-Shi;Choi, Hoon-Sang;Lee, Kwan;Choi, In-Hoon
    • Korean Journal of Materials Research
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    • v.11 no.4
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    • pp.290-293
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    • 2001
  • The SrBi$_2$Nb$_2$O$_{9}$ (SBN) thin films were deposited on p-type(100) Si substrates by rf magnetron sputtering to confirm the Possibility of Pt/SBN/Si structure for the application of nondestructive read out ferroelectric random access memory (NDRO- FRAM). The SBN thin films were deposited by co-sputtering method with Sr$_2$Nb$_2$O$_{7}$ (SNO) and Bi$_2$O$_3$ ceramic targets. The SBN thin films deposited at room temperature were annealed at $700^{\circ}C$ for 1hr in $O_2$ ambient. The structural and electrical properties of SBN with different power ratios of targets were measured by x-ray diffraction(XRD), scanning electron microscopy(SEM), capacitance-voltage(C-V), and current-voltage(I-V). The C-V curves of the SBN films showed hysteresis curves of a clockwise rotation showing ferroelectricity. When the Power ratio of the SNO/Bi$_2$O$_3$ targets was 120 W/100 W, the SBN thin films had excellent electrical properties. The memory window of SBN thin film was 1.8 V-6.3 V at applied voltage of 3 V-9 V and the leakage current density was 1.5 $\times$ 10$^{-7}$ A/$\textrm{cm}^2$ at applied voltage of 5 V The composition of SBN thin films was analysed by electron probe X-ray micro analyzer(EPMA) and the atomic ratio of Sr:Bi:Nb with pawer ratio of 120 W/100 W was 1:3:2.

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Structural and Electrical Properties of K(Ta,Nb)O3 Ceramics with Variation of Ag Contents for Electrocaloric Devices (전기열량소자용 Ag 첨가량에 따른 K(Ta,Nb)O3 세라믹스의 구조적·전기적 특성)

  • Lee, Min-Sung;Park, Byeong-Jun;Lim, Jeong-Eun;Lee, Sam-Haeng;Lee, Myung-Gyu;Park, Joo-Seok;Lee, Sung-Gap
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.34 no.6
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    • pp.442-448
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    • 2021
  • In this work, the (K1-xAgx)(Ta0.8Nb0.2)O3 (x=0.1-0.4) ceramics were fabricated using mixed-oxide method, and their structural and electrical properties were measured. All specimens represented a pseudo cubic structure with the lattice constant of 0.3989 nm. When 0.4 mol of Ag was added, second phases induced from metallic Ag and K2(Ta,Nb)6O16 phase were observed. Dielectric constant and dielectric loss of K(Ta0.8Nb0.2)O3 specimen doped with 0.3 mol of Ag were 2,737 and 0.446, respectively. The curie temperature was about -5℃, which does not change with Ag addition. The remanent polarization began to decrease sharply around 12~15℃, and the temperature at which the remanent polarization began to decrease as the applied voltage increased shifted to the high temperature side. The electrocaloric effect (ΔT) and electrocaloric efficiency (ΔT/ΔE) of the (K0.7Ag0.3)(Ta0.8Nb0.2)O3 ceramics were 0.01024℃ and 0.01825 KmV-1, respectively.

Investigation on Ferroelectric and Magnetic Properties of Pb(Fe1/2Nb1/2)O3 Fe-Site Engineered with Antisymmetric Exchange Interaction (반대칭 교환 상호작용을 갖도록 Fe-Site가 제어된 PbFe1/2Nb1/2O3의 강유전/자기적 특성 연구)

  • Park, Ji-Hun;Lee, Ju-Hyeon;Cho, Jae-Hyeon;Jang, Jong Moon;Jo, Wook
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.35 no.3
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    • pp.297-302
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    • 2022
  • We investigated the origin of magnetic behaviors induced by an asymmetric spin exchange interaction in Fe-site engineered lead iron niobate [Pb(Fe1/2Nb1/2)O3, PFN], which exhibits a room-temperature multiferroicity. The magnitude of spin exchange interaction was regulated by the introduced transition metals with a distinct Bohr magneton, i.e., Cr, Co, and Ni. All compositions were found to have a single-phase perovskite structure keeping their ferroelectric order except for Cr introduction. We discovered that the incorporation of each transition metal imposes a distinct magnetic behavior on the lead iron niobate system; antiferro-, hard ferro-, and soft ferromagnetism for Cr, Co, and Ni, respectively. This indicates that orbital occupancy and interatomic distance play key roles in the determination of magnetic behavior rather than the magnitude of the individual Bohr magneton. Further investigations are planned, such as X-ray absorption spectroscopy, to clarify the origin of magnetic properties in this system.